diff mbox

Btrfs: fix write corruption due to bio cloning on raid5/6

Message ID 20170713140954.2243-1-fdmanana@kernel.org (mailing list archive)
State New, archived
Headers show

Commit Message

Filipe Manana July 13, 2017, 2:09 p.m. UTC 
From: Filipe Manana <fdmanana@suse.com>

The recent changes to make bio cloning faster (added in the 4.13 merge
window) by using the bio_clone_fast() API introduced a regression on
raid5/6 modes, because cloned bios have an invalid bi_vcnt field
(therefore it can not be used) and the raid5/6 code uses the
bio_for_each_segment_all() API to iterate the segments of a bio, and this
API uses a bio's bi_vcnt field.

The issue is very simple to trigger by doing for example a direct IO write
against a raid5 or raid6 filesystem and then attempting to read what we
wrote before:

  $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
  $ mount /dev/sdc /mnt
  $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
  $ od -t x1 /mnt/foobar
  od: /mnt/foobar: read error: Input/output error

For that example, the following is also reported in dmesg/syslog:

  [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
  [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
  [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
  [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
  [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1

A scrub will also fail correcting bad copies, mentioning the following in
dmesg/syslog:

  [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
  [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
  [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
  [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
  [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
  [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
  [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
  [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
  [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
  [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
  [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
  [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
  [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
  [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
  [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
  [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
  [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
  [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
  [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
  [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
  [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
  [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
  [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
  [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
  [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
  [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
  [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
  [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde

So fix this by using the bio_for_each_segment() API and setting before
the bio's bi_iter field to the value of the corresponding btrfs bio
container's saved iterator if we are processing a cloned bio in the
raid5/6 code (the same code processes both cloned and non-cloned bios).

This incorrect iteration of cloned bios was also causing some occasional
BUG_ONs when running fstest btrfs/064, which have a trace like the
following:

  [ 6674.416156] ------------[ cut here ]------------
  [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
  [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
  [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
  [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
  [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
  [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
  [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
  [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
  [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
  [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
  [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
  [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
  [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
  [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
  [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
  [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
  [ 6674.416239] Call Trace:
  [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
  [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
  [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
  [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
  [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
  [ 6674.416331]  bio_endio+0x17d/0x1b3
  [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
  [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
  [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
  [ 6674.416381]  process_one_work+0x276/0x4b6
  [ 6674.416384]  worker_thread+0x1ac/0x266
  [ 6674.416386]  ? rescuer_thread+0x278/0x278
  [ 6674.416387]  kthread+0x106/0x10e
  [ 6674.416389]  ? __list_del_entry+0x22/0x22
  [ 6674.416391]  ret_from_fork+0x27/0x40
  [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
  [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
  [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

Comments

David Sterba July 13, 2017, 4:08 p.m. UTC | #1 
On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The recent changes to make bio cloning faster (added in the 4.13 merge
> window) by using the bio_clone_fast() API introduced a regression on
> raid5/6 modes, because cloned bios have an invalid bi_vcnt field
> (therefore it can not be used) and the raid5/6 code uses the
> bio_for_each_segment_all() API to iterate the segments of a bio, and this
> API uses a bio's bi_vcnt field.

Good catch! I'm going to add assertions to all remaining
bio_for_each_segment_all calls so that cloned bios do not get
accidentally iterated that way.

Other raid levels seem to be fine with the usecase you've provided, I'm
now running fstests with the assertions.
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Liu Bo July 13, 2017, 4:36 p.m. UTC | #2 
On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> The recent changes to make bio cloning faster (added in the 4.13 merge
> window) by using the bio_clone_fast() API introduced a regression on
> raid5/6 modes, because cloned bios have an invalid bi_vcnt field
> (therefore it can not be used) and the raid5/6 code uses the
> bio_for_each_segment_all() API to iterate the segments of a bio, and this
> API uses a bio's bi_vcnt field.
> 
> The issue is very simple to trigger by doing for example a direct IO write
> against a raid5 or raid6 filesystem and then attempting to read what we
> wrote before:
> 
>   $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
>   $ mount /dev/sdc /mnt
>   $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
>   $ od -t x1 /mnt/foobar
>   od: /mnt/foobar: read error: Input/output error
> 
> For that example, the following is also reported in dmesg/syslog:
> 
>   [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
>   [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
>   [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
>   [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>   [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
> 
> A scrub will also fail correcting bad copies, mentioning the following in
> dmesg/syslog:
> 
>   [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
>   [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
>   [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
>   [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>   [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
>   [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>   [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
>   [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>   [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
>   [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>   [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
>   [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>   [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
>   [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
>   [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>   [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
>   [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
>   [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
>   [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>   [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
>   [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
>   [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
>   [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
>   [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
>   [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
>   [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
>   [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
>   [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde
> 
> So fix this by using the bio_for_each_segment() API and setting before
> the bio's bi_iter field to the value of the corresponding btrfs bio
> container's saved iterator if we are processing a cloned bio in the
> raid5/6 code (the same code processes both cloned and non-cloned bios).
> 
> This incorrect iteration of cloned bios was also causing some occasional
> BUG_ONs when running fstest btrfs/064, which have a trace like the
> following:
> 
>   [ 6674.416156] ------------[ cut here ]------------
>   [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
>   [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
>   [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
>   [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
>   [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>   [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
>   [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
>   [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
>   [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
>   [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
>   [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
>   [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
>   [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
>   [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
>   [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
>   [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
>   [ 6674.416239] Call Trace:
>   [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
>   [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
>   [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
>   [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
>   [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
>   [ 6674.416331]  bio_endio+0x17d/0x1b3
>   [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
>   [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
>   [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
>   [ 6674.416381]  process_one_work+0x276/0x4b6
>   [ 6674.416384]  worker_thread+0x1ac/0x266
>   [ 6674.416386]  ? rescuer_thread+0x278/0x278
>   [ 6674.416387]  kthread+0x106/0x10e
>   [ 6674.416389]  ? __list_del_entry+0x22/0x22
>   [ 6674.416391]  ret_from_fork+0x27/0x40
>   [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
>   [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
>   [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---
>

Thank you so much for the fix!


> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> index b9abb0b01021..b89d07003697 100644
> --- a/fs/btrfs/raid56.c
> +++ b/fs/btrfs/raid56.c
> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
>  {
>  	struct bio *bio;
> -	struct bio_vec *bvec;
>  	u64 start;
>  	unsigned long stripe_offset;
>  	unsigned long page_index;
> -	int i;
>  
>  	spin_lock_irq(&rbio->bio_list_lock);
>  	bio_list_for_each(bio, &rbio->bio_list) {
> +		struct bio_vec bvec;
> +		struct bvec_iter iter;
> +		int i = 0;
> +
>  		start = (u64)bio->bi_iter.bi_sector << 9;
>  		stripe_offset = start - rbio->bbio->raid_map[0];
>  		page_index = stripe_offset >> PAGE_SHIFT;
>  
> -		bio_for_each_segment_all(bvec, bio, i)
> -			rbio->bio_pages[page_index + i] = bvec->bv_page;
> +		if (bio_flagged(bio, BIO_CLONED))
> +			bio->bi_iter = btrfs_io_bio(bio)->iter;
> +

I think we can use use bio->bi_iter directly as the bio is not
submitted yet, i.e. bi_iter is not advanced yet.

> +		bio_for_each_segment(bvec, bio, iter) {
> +			rbio->bio_pages[page_index + i] = bvec.bv_page;
> +			i++;
> +		}
>  	}
>  	spin_unlock_irq(&rbio->bio_list_lock);
>  }
> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
>   */
>  static void set_bio_pages_uptodate(struct bio *bio)
>  {
> -	struct bio_vec *bvec;
> -	int i;
> +	struct bio_vec bvec;
> +	struct bvec_iter iter;
> +
> +	if (bio_flagged(bio, BIO_CLONED))
> +		bio->bi_iter = btrfs_io_bio(bio)->iter;
>

Ditto.

Others look good.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

-liubo

> -	bio_for_each_segment_all(bvec, bio, i)
> -		SetPageUptodate(bvec->bv_page);
> +	bio_for_each_segment(bvec, bio, iter)
> +		SetPageUptodate(bvec.bv_page);
>  }
>  
>  /*
> -- 
> 2.11.0
> 
> --
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Filipe Manana July 13, 2017, 4:46 p.m. UTC | #3 
On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
>> From: Filipe Manana <fdmanana@suse.com>
>>
>> The recent changes to make bio cloning faster (added in the 4.13 merge
>> window) by using the bio_clone_fast() API introduced a regression on
>> raid5/6 modes, because cloned bios have an invalid bi_vcnt field
>> (therefore it can not be used) and the raid5/6 code uses the
>> bio_for_each_segment_all() API to iterate the segments of a bio, and this
>> API uses a bio's bi_vcnt field.
>>
>> The issue is very simple to trigger by doing for example a direct IO write
>> against a raid5 or raid6 filesystem and then attempting to read what we
>> wrote before:
>>
>>   $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
>>   $ mount /dev/sdc /mnt
>>   $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
>>   $ od -t x1 /mnt/foobar
>>   od: /mnt/foobar: read error: Input/output error
>>
>> For that example, the following is also reported in dmesg/syslog:
>>
>>   [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
>>   [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
>>   [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
>>   [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>   [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
>>
>> A scrub will also fail correcting bad copies, mentioning the following in
>> dmesg/syslog:
>>
>>   [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
>>   [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
>>   [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
>>   [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>>   [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
>>   [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>>   [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
>>   [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>>   [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
>>   [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>>   [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
>>   [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>>   [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
>>   [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
>>   [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>>   [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
>>   [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
>>   [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
>>   [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>>   [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
>>   [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
>>   [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
>>   [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
>>   [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
>>   [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
>>   [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
>>   [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
>>   [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde
>>
>> So fix this by using the bio_for_each_segment() API and setting before
>> the bio's bi_iter field to the value of the corresponding btrfs bio
>> container's saved iterator if we are processing a cloned bio in the
>> raid5/6 code (the same code processes both cloned and non-cloned bios).
>>
>> This incorrect iteration of cloned bios was also causing some occasional
>> BUG_ONs when running fstest btrfs/064, which have a trace like the
>> following:
>>
>>   [ 6674.416156] ------------[ cut here ]------------
>>   [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
>>   [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
>>   [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
>>   [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
>>   [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>>   [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
>>   [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
>>   [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
>>   [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
>>   [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
>>   [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
>>   [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
>>   [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
>>   [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
>>   [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
>>   [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>   [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
>>   [ 6674.416239] Call Trace:
>>   [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
>>   [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
>>   [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
>>   [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
>>   [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
>>   [ 6674.416331]  bio_endio+0x17d/0x1b3
>>   [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
>>   [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
>>   [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
>>   [ 6674.416381]  process_one_work+0x276/0x4b6
>>   [ 6674.416384]  worker_thread+0x1ac/0x266
>>   [ 6674.416386]  ? rescuer_thread+0x278/0x278
>>   [ 6674.416387]  kthread+0x106/0x10e
>>   [ 6674.416389]  ? __list_del_entry+0x22/0x22
>>   [ 6674.416391]  ret_from_fork+0x27/0x40
>>   [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
>>   [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
>>   [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---
>>
>
> Thank you so much for the fix!
>
>
>> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>> ---
>>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
>>  1 file changed, 18 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
>> index b9abb0b01021..b89d07003697 100644
>> --- a/fs/btrfs/raid56.c
>> +++ b/fs/btrfs/raid56.c
>> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
>>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
>>  {
>>       struct bio *bio;
>> -     struct bio_vec *bvec;
>>       u64 start;
>>       unsigned long stripe_offset;
>>       unsigned long page_index;
>> -     int i;
>>
>>       spin_lock_irq(&rbio->bio_list_lock);
>>       bio_list_for_each(bio, &rbio->bio_list) {
>> +             struct bio_vec bvec;
>> +             struct bvec_iter iter;
>> +             int i = 0;
>> +
>>               start = (u64)bio->bi_iter.bi_sector << 9;
>>               stripe_offset = start - rbio->bbio->raid_map[0];
>>               page_index = stripe_offset >> PAGE_SHIFT;
>>
>> -             bio_for_each_segment_all(bvec, bio, i)
>> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
>> +             if (bio_flagged(bio, BIO_CLONED))
>> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
>> +
>
> I think we can use use bio->bi_iter directly as the bio is not
> submitted yet, i.e. bi_iter is not advanced yet.

I've seen it cause problems by not setting it. I.e. the bio was
iterated before somewhere else.
Which lead to the following trace:

[ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
[ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
i2c_core button sunrpc loop auto
fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
crc32c_generic raid1 raid0 multipath line
ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
btrfs]
[ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
4.12.0-rc6-btrfs-next-47+ #1
[ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
[ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
[ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
[ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
[ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
[ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
[ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
[ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
[ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
[ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
knlGS:0000000000000000
[ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
[ 3955.731730] Call Trace:
[ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
[ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
[ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
[ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
[ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
[ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
[ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
[ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
[ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
[ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
[ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
[ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
[ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
[ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
[ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
[ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
[ 3955.731730]  do_writepages+0x3c/0x72
[ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
[ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
[ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
[ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
[ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
[ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
[ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
[ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
[ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
[ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
[ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
[ 3955.731730]  mount_fs+0x67/0x114
[ 3955.731730]  vfs_kern_mount+0x6b/0xdb
[ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
[ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
[ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
[ 3955.731730]  mount_fs+0x67/0x114
[ 3955.731730]  vfs_kern_mount+0x6b/0xdb
[ 3955.731730]  do_mount+0x6e3/0x96d
[ 3955.731730]  ? strndup_user+0x3f/0x73
[ 3955.731730]  SyS_mount+0x77/0x9f
[ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
[ 3955.731730] RIP: 0033:0x7f68fd12a0ba
[ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
00000000000000a5
[ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
[ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
[ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
[ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
[ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
[ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
[ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
31 c9
[ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
[ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---


>
>> +             bio_for_each_segment(bvec, bio, iter) {
>> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
>> +                     i++;
>> +             }
>>       }
>>       spin_unlock_irq(&rbio->bio_list_lock);
>>  }
>> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
>>   */
>>  static void set_bio_pages_uptodate(struct bio *bio)
>>  {
>> -     struct bio_vec *bvec;
>> -     int i;
>> +     struct bio_vec bvec;
>> +     struct bvec_iter iter;
>> +
>> +     if (bio_flagged(bio, BIO_CLONED))
>> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
>>
>
> Ditto.
>
> Others look good.
>
> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
>
> -liubo
>
>> -     bio_for_each_segment_all(bvec, bio, i)
>> -             SetPageUptodate(bvec->bv_page);
>> +     bio_for_each_segment(bvec, bio, iter)
>> +             SetPageUptodate(bvec.bv_page);
>>  }
>>
>>  /*
>> --
>> 2.11.0
>>
>> --
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Liu Bo July 13, 2017, 5:06 p.m. UTC | #4 
On Thu, Jul 13, 2017 at 05:46:13PM +0100, Filipe Manana wrote:
> On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> > On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> >> From: Filipe Manana <fdmanana@suse.com>
> >>
[...]
> >
> >
> >> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> >> ---
> >>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
> >>  1 file changed, 18 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> >> index b9abb0b01021..b89d07003697 100644
> >> --- a/fs/btrfs/raid56.c
> >> +++ b/fs/btrfs/raid56.c
> >> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
> >>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
> >>  {
> >>       struct bio *bio;
> >> -     struct bio_vec *bvec;
> >>       u64 start;
> >>       unsigned long stripe_offset;
> >>       unsigned long page_index;
> >> -     int i;
> >>
> >>       spin_lock_irq(&rbio->bio_list_lock);
> >>       bio_list_for_each(bio, &rbio->bio_list) {
> >> +             struct bio_vec bvec;
> >> +             struct bvec_iter iter;
> >> +             int i = 0;
> >> +
> >>               start = (u64)bio->bi_iter.bi_sector << 9;
> >>               stripe_offset = start - rbio->bbio->raid_map[0];
> >>               page_index = stripe_offset >> PAGE_SHIFT;
> >>
> >> -             bio_for_each_segment_all(bvec, bio, i)
> >> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
> >> +             if (bio_flagged(bio, BIO_CLONED))
> >> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> +
> >
> > I think we can use use bio->bi_iter directly as the bio is not
> > submitted yet, i.e. bi_iter is not advanced yet.
> 
> I've seen it cause problems by not setting it. I.e. the bio was
> iterated before somewhere else.
> Which lead to the following trace:
>

This is coming from a free space inode flush during mount time and
it's full of buffered writes, the bio in use is not a cloned one.

Interesting...let me check locally.

-liubo

> [ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
> [ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
> parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
> i2c_core button sunrpc loop auto
> fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
> async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
> crc32c_generic raid1 raid0 multipath line
> ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
> virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
> btrfs]
> [ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
> 4.12.0-rc6-btrfs-next-47+ #1
> [ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
> [ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
> [ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
> [ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
> [ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
> [ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
> [ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
> [ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
> [ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
> [ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
> knlGS:0000000000000000
> [ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
> [ 3955.731730] Call Trace:
> [ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
> [ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
> [ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
> [ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
> [ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
> [ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
> [ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
> [ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
> [ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
> [ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
> [ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
> [ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
> [ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
> [ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
> [ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
> [ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
> [ 3955.731730]  do_writepages+0x3c/0x72
> [ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
> [ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
> [ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
> [ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
> [ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
> [ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
> [ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
> [ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
> [ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
> [ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
> [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> [ 3955.731730]  mount_fs+0x67/0x114
> [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> [ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
> [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> [ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
> [ 3955.731730]  mount_fs+0x67/0x114
> [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> [ 3955.731730]  do_mount+0x6e3/0x96d
> [ 3955.731730]  ? strndup_user+0x3f/0x73
> [ 3955.731730]  SyS_mount+0x77/0x9f
> [ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
> [ 3955.731730] RIP: 0033:0x7f68fd12a0ba
> [ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
> 00000000000000a5
> [ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
> [ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
> [ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
> [ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
> [ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
> [ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
> [ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
> 15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
> c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
> 31 c9
> [ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
> [ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---
> 
> 
> >
> >> +             bio_for_each_segment(bvec, bio, iter) {
> >> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
> >> +                     i++;
> >> +             }
> >>       }
> >>       spin_unlock_irq(&rbio->bio_list_lock);
> >>  }
> >> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> >>   */
> >>  static void set_bio_pages_uptodate(struct bio *bio)
> >>  {
> >> -     struct bio_vec *bvec;
> >> -     int i;
> >> +     struct bio_vec bvec;
> >> +     struct bvec_iter iter;
> >> +
> >> +     if (bio_flagged(bio, BIO_CLONED))
> >> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
> >>
> >
> > Ditto.
> >
> > Others look good.
> >
> > Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> >
> > -liubo
> >
> >> -     bio_for_each_segment_all(bvec, bio, i)
> >> -             SetPageUptodate(bvec->bv_page);
> >> +     bio_for_each_segment(bvec, bio, iter)
> >> +             SetPageUptodate(bvec.bv_page);
> >>  }
> >>
> >>  /*
> >> --
> >> 2.11.0
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
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Liu Bo July 13, 2017, 6 p.m. UTC | #5 
On Thu, Jul 13, 2017 at 10:06:32AM -0700, Liu Bo wrote:
> On Thu, Jul 13, 2017 at 05:46:13PM +0100, Filipe Manana wrote:
> > On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> > > On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> > >> From: Filipe Manana <fdmanana@suse.com>
> > >>
> [...]
> > >
> > >
> > >> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> > >> ---
> > >>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
> > >>  1 file changed, 18 insertions(+), 8 deletions(-)
> > >>
> > >> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> > >> index b9abb0b01021..b89d07003697 100644
> > >> --- a/fs/btrfs/raid56.c
> > >> +++ b/fs/btrfs/raid56.c
> > >> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
> > >>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
> > >>  {
> > >>       struct bio *bio;
> > >> -     struct bio_vec *bvec;
> > >>       u64 start;
> > >>       unsigned long stripe_offset;
> > >>       unsigned long page_index;
> > >> -     int i;
> > >>
> > >>       spin_lock_irq(&rbio->bio_list_lock);
> > >>       bio_list_for_each(bio, &rbio->bio_list) {
> > >> +             struct bio_vec bvec;
> > >> +             struct bvec_iter iter;
> > >> +             int i = 0;
> > >> +
> > >>               start = (u64)bio->bi_iter.bi_sector << 9;
> > >>               stripe_offset = start - rbio->bbio->raid_map[0];
> > >>               page_index = stripe_offset >> PAGE_SHIFT;
> > >>
> > >> -             bio_for_each_segment_all(bvec, bio, i)
> > >> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
> > >> +             if (bio_flagged(bio, BIO_CLONED))
> > >> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
> > >> +
> > >
> > > I think we can use use bio->bi_iter directly as the bio is not
> > > submitted yet, i.e. bi_iter is not advanced yet.
> > 
> > I've seen it cause problems by not setting it. I.e. the bio was
> > iterated before somewhere else.
> > Which lead to the following trace:
> >
> 
> This is coming from a free space inode flush during mount time and
> it's full of buffered writes, the bio in use is not a cloned one.
> 
> Interesting...let me check locally.
>

I ran the mentioned script in the commit log without the part of
setting bio->bi_iter to btrfs_io_bio(bio)->iter.

$ mkfs.btrfs -f -d raid5 /dev/sd[cde]

$ mount /dev/sde /mnt/btrfs

$ xfs_io -f -d -c "pwrite 0 128K" /mnt/btrfs/foobar
wrote 131072/131072 bytes at offset 0
128 KiB, 32 ops; 0.0000 sec (5.842 MiB/sec and 1495.6766 ops/sec)

$ od -t x1 /mnt/btrfs/foobar 
0000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
*
0400000

$ uname -r
4.12.0+

It works fine without causing 'generic protection' during mount.

thanks,

-liubo

> -liubo
> 
> > [ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
> > [ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
> > parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
> > i2c_core button sunrpc loop auto
> > fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
> > async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
> > crc32c_generic raid1 raid0 multipath line
> > ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
> > virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
> > btrfs]
> > [ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
> > 4.12.0-rc6-btrfs-next-47+ #1
> > [ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> > BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
> > [ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
> > [ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
> > [ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
> > [ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
> > [ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
> > [ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
> > [ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
> > [ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
> > [ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
> > knlGS:0000000000000000
> > [ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
> > [ 3955.731730] Call Trace:
> > [ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
> > [ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
> > [ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
> > [ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
> > [ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
> > [ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
> > [ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
> > [ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
> > [ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
> > [ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
> > [ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
> > [ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
> > [ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
> > [ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
> > [ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
> > [ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
> > [ 3955.731730]  do_writepages+0x3c/0x72
> > [ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
> > [ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
> > [ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
> > [ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
> > [ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
> > [ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
> > [ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
> > [ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
> > [ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
> > [ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> > [ 3955.731730]  mount_fs+0x67/0x114
> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> > [ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> > [ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
> > [ 3955.731730]  mount_fs+0x67/0x114
> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> > [ 3955.731730]  do_mount+0x6e3/0x96d
> > [ 3955.731730]  ? strndup_user+0x3f/0x73
> > [ 3955.731730]  SyS_mount+0x77/0x9f
> > [ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
> > [ 3955.731730] RIP: 0033:0x7f68fd12a0ba
> > [ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
> > 00000000000000a5
> > [ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
> > [ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
> > [ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
> > [ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
> > [ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
> > [ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
> > [ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
> > 15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
> > c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
> > 31 c9
> > [ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
> > [ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---
> > 
> > 
> > >
> > >> +             bio_for_each_segment(bvec, bio, iter) {
> > >> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
> > >> +                     i++;
> > >> +             }
> > >>       }
> > >>       spin_unlock_irq(&rbio->bio_list_lock);
> > >>  }
> > >> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> > >>   */
> > >>  static void set_bio_pages_uptodate(struct bio *bio)
> > >>  {
> > >> -     struct bio_vec *bvec;
> > >> -     int i;
> > >> +     struct bio_vec bvec;
> > >> +     struct bvec_iter iter;
> > >> +
> > >> +     if (bio_flagged(bio, BIO_CLONED))
> > >> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
> > >>
> > >
> > > Ditto.
> > >
> > > Others look good.
> > >
> > > Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> > >
> > > -liubo
> > >
> > >> -     bio_for_each_segment_all(bvec, bio, i)
> > >> -             SetPageUptodate(bvec->bv_page);
> > >> +     bio_for_each_segment(bvec, bio, iter)
> > >> +             SetPageUptodate(bvec.bv_page);
> > >>  }
> > >>
> > >>  /*
> > >> --
> > >> 2.11.0
> > >>
> > >> --
> > >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> > >> the body of a message to majordomo@vger.kernel.org
> > >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
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Filipe Manana July 13, 2017, 6:11 p.m. UTC | #6 
On Thu, Jul 13, 2017 at 7:00 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> On Thu, Jul 13, 2017 at 10:06:32AM -0700, Liu Bo wrote:
>> On Thu, Jul 13, 2017 at 05:46:13PM +0100, Filipe Manana wrote:
>> > On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
>> > > On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
>> > >> From: Filipe Manana <fdmanana@suse.com>
>> > >>
>> [...]
>> > >
>> > >
>> > >> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>> > >> ---
>> > >>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
>> > >>  1 file changed, 18 insertions(+), 8 deletions(-)
>> > >>
>> > >> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
>> > >> index b9abb0b01021..b89d07003697 100644
>> > >> --- a/fs/btrfs/raid56.c
>> > >> +++ b/fs/btrfs/raid56.c
>> > >> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
>> > >>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
>> > >>  {
>> > >>       struct bio *bio;
>> > >> -     struct bio_vec *bvec;
>> > >>       u64 start;
>> > >>       unsigned long stripe_offset;
>> > >>       unsigned long page_index;
>> > >> -     int i;
>> > >>
>> > >>       spin_lock_irq(&rbio->bio_list_lock);
>> > >>       bio_list_for_each(bio, &rbio->bio_list) {
>> > >> +             struct bio_vec bvec;
>> > >> +             struct bvec_iter iter;
>> > >> +             int i = 0;
>> > >> +
>> > >>               start = (u64)bio->bi_iter.bi_sector << 9;
>> > >>               stripe_offset = start - rbio->bbio->raid_map[0];
>> > >>               page_index = stripe_offset >> PAGE_SHIFT;
>> > >>
>> > >> -             bio_for_each_segment_all(bvec, bio, i)
>> > >> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
>> > >> +             if (bio_flagged(bio, BIO_CLONED))
>> > >> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
>> > >> +
>> > >
>> > > I think we can use use bio->bi_iter directly as the bio is not
>> > > submitted yet, i.e. bi_iter is not advanced yet.
>> >
>> > I've seen it cause problems by not setting it. I.e. the bio was
>> > iterated before somewhere else.
>> > Which lead to the following trace:
>> >
>>
>> This is coming from a free space inode flush during mount time and
>> it's full of buffered writes, the bio in use is not a cloned one.
>>
>> Interesting...let me check locally.
>>
>
> I ran the mentioned script in the commit log without the part of
> setting bio->bi_iter to btrfs_io_bio(bio)->iter.
>
> $ mkfs.btrfs -f -d raid5 /dev/sd[cde]
>
> $ mount /dev/sde /mnt/btrfs
>
> $ xfs_io -f -d -c "pwrite 0 128K" /mnt/btrfs/foobar
> wrote 131072/131072 bytes at offset 0
> 128 KiB, 32 ops; 0.0000 sec (5.842 MiB/sec and 1495.6766 ops/sec)
>
> $ od -t x1 /mnt/btrfs/foobar
> 0000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
> *
> 0400000
>
> $ uname -r
> 4.12.0+
>
> It works fine without causing 'generic protection' during mount.

Yes, the trace was not from running the test mentioned in the
changelog, but rather btrfs/0[60-74] iirc or some other stress tests.
It doesn't happen always as well.

>
> thanks,
>
> -liubo
>
>> -liubo
>>
>> > [ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
>> > [ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
>> > parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
>> > i2c_core button sunrpc loop auto
>> > fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
>> > async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
>> > crc32c_generic raid1 raid0 multipath line
>> > ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
>> > virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
>> > btrfs]
>> > [ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
>> > 4.12.0-rc6-btrfs-next-47+ #1
>> > [ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> > BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>> > [ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
>> > [ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
>> > [ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
>> > [ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
>> > [ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
>> > [ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
>> > [ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
>> > [ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
>> > [ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
>> > knlGS:0000000000000000
>> > [ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > [ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
>> > [ 3955.731730] Call Trace:
>> > [ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
>> > [ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
>> > [ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
>> > [ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
>> > [ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
>> > [ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
>> > [ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
>> > [ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
>> > [ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
>> > [ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
>> > [ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
>> > [ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
>> > [ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
>> > [ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
>> > [ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
>> > [ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
>> > [ 3955.731730]  do_writepages+0x3c/0x72
>> > [ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
>> > [ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
>> > [ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
>> > [ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
>> > [ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
>> > [ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
>> > [ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
>> > [ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
>> > [ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
>> > [ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
>> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
>> > [ 3955.731730]  mount_fs+0x67/0x114
>> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
>> > [ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
>> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
>> > [ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
>> > [ 3955.731730]  mount_fs+0x67/0x114
>> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
>> > [ 3955.731730]  do_mount+0x6e3/0x96d
>> > [ 3955.731730]  ? strndup_user+0x3f/0x73
>> > [ 3955.731730]  SyS_mount+0x77/0x9f
>> > [ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
>> > [ 3955.731730] RIP: 0033:0x7f68fd12a0ba
>> > [ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
>> > 00000000000000a5
>> > [ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
>> > [ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
>> > [ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
>> > [ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
>> > [ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
>> > [ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
>> > [ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
>> > 15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
>> > c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
>> > 31 c9
>> > [ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
>> > [ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---
>> >
>> >
>> > >
>> > >> +             bio_for_each_segment(bvec, bio, iter) {
>> > >> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
>> > >> +                     i++;
>> > >> +             }
>> > >>       }
>> > >>       spin_unlock_irq(&rbio->bio_list_lock);
>> > >>  }
>> > >> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
>> > >>   */
>> > >>  static void set_bio_pages_uptodate(struct bio *bio)
>> > >>  {
>> > >> -     struct bio_vec *bvec;
>> > >> -     int i;
>> > >> +     struct bio_vec bvec;
>> > >> +     struct bvec_iter iter;
>> > >> +
>> > >> +     if (bio_flagged(bio, BIO_CLONED))
>> > >> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
>> > >>
>> > >
>> > > Ditto.
>> > >
>> > > Others look good.
>> > >
>> > > Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
>> > >
>> > > -liubo
>> > >
>> > >> -     bio_for_each_segment_all(bvec, bio, i)
>> > >> -             SetPageUptodate(bvec->bv_page);
>> > >> +     bio_for_each_segment(bvec, bio, iter)
>> > >> +             SetPageUptodate(bvec.bv_page);
>> > >>  }
>> > >>
>> > >>  /*
>> > >> --
>> > >> 2.11.0
>> > >>
>> > >> --
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Liu Bo July 13, 2017, 7:09 p.m. UTC | #7 
On Thu, Jul 13, 2017 at 07:11:24PM +0100, Filipe Manana wrote:
> On Thu, Jul 13, 2017 at 7:00 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> > On Thu, Jul 13, 2017 at 10:06:32AM -0700, Liu Bo wrote:
> >> On Thu, Jul 13, 2017 at 05:46:13PM +0100, Filipe Manana wrote:
> >> > On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> >> > > On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> >> > >> From: Filipe Manana <fdmanana@suse.com>
> >> > >>
> >> [...]
> >> > >
> >> > >
> >> > >> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> >> > >> ---
> >> > >>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
> >> > >>  1 file changed, 18 insertions(+), 8 deletions(-)
> >> > >>
> >> > >> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> >> > >> index b9abb0b01021..b89d07003697 100644
> >> > >> --- a/fs/btrfs/raid56.c
> >> > >> +++ b/fs/btrfs/raid56.c
> >> > >> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
> >> > >>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
> >> > >>  {
> >> > >>       struct bio *bio;
> >> > >> -     struct bio_vec *bvec;
> >> > >>       u64 start;
> >> > >>       unsigned long stripe_offset;
> >> > >>       unsigned long page_index;
> >> > >> -     int i;
> >> > >>
> >> > >>       spin_lock_irq(&rbio->bio_list_lock);
> >> > >>       bio_list_for_each(bio, &rbio->bio_list) {
> >> > >> +             struct bio_vec bvec;
> >> > >> +             struct bvec_iter iter;
> >> > >> +             int i = 0;
> >> > >> +
> >> > >>               start = (u64)bio->bi_iter.bi_sector << 9;
> >> > >>               stripe_offset = start - rbio->bbio->raid_map[0];
> >> > >>               page_index = stripe_offset >> PAGE_SHIFT;
> >> > >>
> >> > >> -             bio_for_each_segment_all(bvec, bio, i)
> >> > >> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
> >> > >> +             if (bio_flagged(bio, BIO_CLONED))
> >> > >> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> > >> +
> >> > >
> >> > > I think we can use use bio->bi_iter directly as the bio is not
> >> > > submitted yet, i.e. bi_iter is not advanced yet.
> >> >
> >> > I've seen it cause problems by not setting it. I.e. the bio was
> >> > iterated before somewhere else.
> >> > Which lead to the following trace:
> >> >
> >>
> >> This is coming from a free space inode flush during mount time and
> >> it's full of buffered writes, the bio in use is not a cloned one.
> >>
> >> Interesting...let me check locally.
> >>
> >
> > I ran the mentioned script in the commit log without the part of
> > setting bio->bi_iter to btrfs_io_bio(bio)->iter.
> >
> > $ mkfs.btrfs -f -d raid5 /dev/sd[cde]
> >
> > $ mount /dev/sde /mnt/btrfs
> >
> > $ xfs_io -f -d -c "pwrite 0 128K" /mnt/btrfs/foobar
> > wrote 131072/131072 bytes at offset 0
> > 128 KiB, 32 ops; 0.0000 sec (5.842 MiB/sec and 1495.6766 ops/sec)
> >
> > $ od -t x1 /mnt/btrfs/foobar
> > 0000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
> > *
> > 0400000
> >
> > $ uname -r
> > 4.12.0+
> >
> > It works fine without causing 'generic protection' during mount.
> 
> Yes, the trace was not from running the test mentioned in the
> changelog, but rather btrfs/0[60-74] iirc or some other stress tests.
> It doesn't happen always as well.
>

I see, then it might be caused by some other problems, as the trace
shows, it's a buffered write whose bio is not cloned, so it still
takes bio->bi_iter for the iteration.

The 'general protection' was in finish_rmw(), could you please check
if that points to somewhere inside this bio_for_each_segment() helper?

thanks,

-liubo

> >
> > thanks,
> >
> > -liubo
> >
> >> -liubo
> >>
> >> > [ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
> >> > [ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
> >> > parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
> >> > i2c_core button sunrpc loop auto
> >> > fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
> >> > async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
> >> > crc32c_generic raid1 raid0 multipath line
> >> > ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
> >> > virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
> >> > btrfs]
> >> > [ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
> >> > 4.12.0-rc6-btrfs-next-47+ #1
> >> > [ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> >> > BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
> >> > [ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
> >> > [ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
> >> > [ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
> >> > [ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
> >> > [ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
> >> > [ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
> >> > [ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
> >> > [ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
> >> > [ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
> >> > knlGS:0000000000000000
> >> > [ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> > [ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
> >> > [ 3955.731730] Call Trace:
> >> > [ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
> >> > [ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
> >> > [ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
> >> > [ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
> >> > [ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
> >> > [ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
> >> > [ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
> >> > [ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
> >> > [ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
> >> > [ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
> >> > [ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
> >> > [ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
> >> > [ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
> >> > [ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
> >> > [ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
> >> > [ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
> >> > [ 3955.731730]  do_writepages+0x3c/0x72
> >> > [ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
> >> > [ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
> >> > [ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
> >> > [ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
> >> > [ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
> >> > [ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
> >> > [ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
> >> > [ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
> >> > [ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
> >> > [ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
> >> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> >> > [ 3955.731730]  mount_fs+0x67/0x114
> >> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> >> > [ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
> >> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
> >> > [ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
> >> > [ 3955.731730]  mount_fs+0x67/0x114
> >> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
> >> > [ 3955.731730]  do_mount+0x6e3/0x96d
> >> > [ 3955.731730]  ? strndup_user+0x3f/0x73
> >> > [ 3955.731730]  SyS_mount+0x77/0x9f
> >> > [ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
> >> > [ 3955.731730] RIP: 0033:0x7f68fd12a0ba
> >> > [ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
> >> > 00000000000000a5
> >> > [ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
> >> > [ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
> >> > [ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
> >> > [ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
> >> > [ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
> >> > [ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
> >> > [ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
> >> > 15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
> >> > c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
> >> > 31 c9
> >> > [ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
> >> > [ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---
> >> >
> >> >
> >> > >
> >> > >> +             bio_for_each_segment(bvec, bio, iter) {
> >> > >> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
> >> > >> +                     i++;
> >> > >> +             }
> >> > >>       }
> >> > >>       spin_unlock_irq(&rbio->bio_list_lock);
> >> > >>  }
> >> > >> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> >> > >>   */
> >> > >>  static void set_bio_pages_uptodate(struct bio *bio)
> >> > >>  {
> >> > >> -     struct bio_vec *bvec;
> >> > >> -     int i;
> >> > >> +     struct bio_vec bvec;
> >> > >> +     struct bvec_iter iter;
> >> > >> +
> >> > >> +     if (bio_flagged(bio, BIO_CLONED))
> >> > >> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> > >>
> >> > >
> >> > > Ditto.
> >> > >
> >> > > Others look good.
> >> > >
> >> > > Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> >> > >
> >> > > -liubo
> >> > >
> >> > >> -     bio_for_each_segment_all(bvec, bio, i)
> >> > >> -             SetPageUptodate(bvec->bv_page);
> >> > >> +     bio_for_each_segment(bvec, bio, iter)
> >> > >> +             SetPageUptodate(bvec.bv_page);
> >> > >>  }
> >> > >>
> >> > >>  /*
> >> > >> --
> >> > >> 2.11.0
> >> > >>
> >> > >> --
> >> > >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> >> > >> the body of a message to majordomo@vger.kernel.org
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Liu Bo July 13, 2017, 10:38 p.m. UTC | #8 
On Thu, Jul 13, 2017 at 09:36:19AM -0700, Liu Bo wrote:
> On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> > 
> > The recent changes to make bio cloning faster (added in the 4.13 merge
> > window) by using the bio_clone_fast() API introduced a regression on
> > raid5/6 modes, because cloned bios have an invalid bi_vcnt field
> > (therefore it can not be used) and the raid5/6 code uses the
> > bio_for_each_segment_all() API to iterate the segments of a bio, and this
> > API uses a bio's bi_vcnt field.
> > 
> > The issue is very simple to trigger by doing for example a direct IO write
> > against a raid5 or raid6 filesystem and then attempting to read what we
> > wrote before:
> > 
> >   $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
> >   $ mount /dev/sdc /mnt
> >   $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
> >   $ od -t x1 /mnt/foobar
> >   od: /mnt/foobar: read error: Input/output error
> > 
> > For that example, the following is also reported in dmesg/syslog:
> > 
> >   [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
> >   [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
> >   [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
> >   [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >   [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
> > 
> > A scrub will also fail correcting bad copies, mentioning the following in
> > dmesg/syslog:
> > 
> >   [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
> >   [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
> >   [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
> >   [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >   [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
> >   [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >   [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
> >   [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
> >   [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
> >   [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >   [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
> >   [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
> >   [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
> >   [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
> >   [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
> >   [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
> >   [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
> >   [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
> >   [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
> >   [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
> >   [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
> >   [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
> >   [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
> >   [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
> >   [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
> >   [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
> >   [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
> >   [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde
> > 
> > So fix this by using the bio_for_each_segment() API and setting before
> > the bio's bi_iter field to the value of the corresponding btrfs bio
> > container's saved iterator if we are processing a cloned bio in the
> > raid5/6 code (the same code processes both cloned and non-cloned bios).
> > 
> > This incorrect iteration of cloned bios was also causing some occasional
> > BUG_ONs when running fstest btrfs/064, which have a trace like the
> > following:
> > 
> >   [ 6674.416156] ------------[ cut here ]------------
> >   [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
> >   [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
> >   [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
> >   [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
> >   [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
> >   [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
> >   [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
> >   [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
> >   [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
> >   [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
> >   [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
> >   [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
> >   [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
> >   [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
> >   [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
> >   [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >   [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
> >   [ 6674.416239] Call Trace:
> >   [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
> >   [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
> >   [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
> >   [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
> >   [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
> >   [ 6674.416331]  bio_endio+0x17d/0x1b3
> >   [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
> >   [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
> >   [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
> >   [ 6674.416381]  process_one_work+0x276/0x4b6
> >   [ 6674.416384]  worker_thread+0x1ac/0x266
> >   [ 6674.416386]  ? rescuer_thread+0x278/0x278
> >   [ 6674.416387]  kthread+0x106/0x10e
> >   [ 6674.416389]  ? __list_del_entry+0x22/0x22
> >   [ 6674.416391]  ret_from_fork+0x27/0x40
> >   [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
> >   [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
> >   [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---
> >
> 
> Thank you so much for the fix!
> 
> 
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> > ---
> >  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
> >  1 file changed, 18 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> > index b9abb0b01021..b89d07003697 100644
> > --- a/fs/btrfs/raid56.c
> > +++ b/fs/btrfs/raid56.c
> > @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
> >  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
> >  {
> >  	struct bio *bio;
> > -	struct bio_vec *bvec;
> >  	u64 start;
> >  	unsigned long stripe_offset;
> >  	unsigned long page_index;
> > -	int i;
> >  
> >  	spin_lock_irq(&rbio->bio_list_lock);
> >  	bio_list_for_each(bio, &rbio->bio_list) {
> > +		struct bio_vec bvec;
> > +		struct bvec_iter iter;
> > +		int i = 0;
> > +
> >  		start = (u64)bio->bi_iter.bi_sector << 9;
> >  		stripe_offset = start - rbio->bbio->raid_map[0];
> >  		page_index = stripe_offset >> PAGE_SHIFT;
> >  
> > -		bio_for_each_segment_all(bvec, bio, i)
> > -			rbio->bio_pages[page_index + i] = bvec->bv_page;
> > +		if (bio_flagged(bio, BIO_CLONED))
> > +			bio->bi_iter = btrfs_io_bio(bio)->iter;
> > +
> 
> I think we can use use bio->bi_iter directly as the bio is not
> submitted yet, i.e. bi_iter is not advanced yet.
> 
> > +		bio_for_each_segment(bvec, bio, iter) {
> > +			rbio->bio_pages[page_index + i] = bvec.bv_page;
> > +			i++;
> > +		}
> >  	}
> >  	spin_unlock_irq(&rbio->bio_list_lock);
> >  }
> > @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> >   */
> >  static void set_bio_pages_uptodate(struct bio *bio)
> >  {
> > -	struct bio_vec *bvec;
> > -	int i;
> > +	struct bio_vec bvec;
> > +	struct bvec_iter iter;
> > +
> > +	if (bio_flagged(bio, BIO_CLONED))
> > +		bio->bi_iter = btrfs_io_bio(bio)->iter;
> >

It is not necessary to update set_bio_pages_uptodate() because the bio
here is for reading pages in RMW and no way it could be a cloned one.

thanks,

-liubo

> 
> Ditto.
> 
> Others look good.
> 
> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> 
> -liubo
> 
> > -	bio_for_each_segment_all(bvec, bio, i)
> > -		SetPageUptodate(bvec->bv_page);
> > +	bio_for_each_segment(bvec, bio, iter)
> > +		SetPageUptodate(bvec.bv_page);
> >  }
> >  
> >  /*
> > -- 
> > 2.11.0
> > 
> > --
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Filipe Manana July 14, 2017, 8:51 a.m. UTC | #9 
On Thu, Jul 13, 2017 at 8:09 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> On Thu, Jul 13, 2017 at 07:11:24PM +0100, Filipe Manana wrote:
>> On Thu, Jul 13, 2017 at 7:00 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
>> > On Thu, Jul 13, 2017 at 10:06:32AM -0700, Liu Bo wrote:
>> >> On Thu, Jul 13, 2017 at 05:46:13PM +0100, Filipe Manana wrote:
>> >> > On Thu, Jul 13, 2017 at 5:36 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
>> >> > > On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
>> >> > >> From: Filipe Manana <fdmanana@suse.com>
>> >> > >>
>> >> [...]
>> >> > >
>> >> > >
>> >> > >> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>> >> > >> ---
>> >> > >>  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
>> >> > >>  1 file changed, 18 insertions(+), 8 deletions(-)
>> >> > >>
>> >> > >> diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
>> >> > >> index b9abb0b01021..b89d07003697 100644
>> >> > >> --- a/fs/btrfs/raid56.c
>> >> > >> +++ b/fs/btrfs/raid56.c
>> >> > >> @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
>> >> > >>  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
>> >> > >>  {
>> >> > >>       struct bio *bio;
>> >> > >> -     struct bio_vec *bvec;
>> >> > >>       u64 start;
>> >> > >>       unsigned long stripe_offset;
>> >> > >>       unsigned long page_index;
>> >> > >> -     int i;
>> >> > >>
>> >> > >>       spin_lock_irq(&rbio->bio_list_lock);
>> >> > >>       bio_list_for_each(bio, &rbio->bio_list) {
>> >> > >> +             struct bio_vec bvec;
>> >> > >> +             struct bvec_iter iter;
>> >> > >> +             int i = 0;
>> >> > >> +
>> >> > >>               start = (u64)bio->bi_iter.bi_sector << 9;
>> >> > >>               stripe_offset = start - rbio->bbio->raid_map[0];
>> >> > >>               page_index = stripe_offset >> PAGE_SHIFT;
>> >> > >>
>> >> > >> -             bio_for_each_segment_all(bvec, bio, i)
>> >> > >> -                     rbio->bio_pages[page_index + i] = bvec->bv_page;
>> >> > >> +             if (bio_flagged(bio, BIO_CLONED))
>> >> > >> +                     bio->bi_iter = btrfs_io_bio(bio)->iter;
>> >> > >> +
>> >> > >
>> >> > > I think we can use use bio->bi_iter directly as the bio is not
>> >> > > submitted yet, i.e. bi_iter is not advanced yet.
>> >> >
>> >> > I've seen it cause problems by not setting it. I.e. the bio was
>> >> > iterated before somewhere else.
>> >> > Which lead to the following trace:
>> >> >
>> >>
>> >> This is coming from a free space inode flush during mount time and
>> >> it's full of buffered writes, the bio in use is not a cloned one.
>> >>
>> >> Interesting...let me check locally.
>> >>
>> >
>> > I ran the mentioned script in the commit log without the part of
>> > setting bio->bi_iter to btrfs_io_bio(bio)->iter.
>> >
>> > $ mkfs.btrfs -f -d raid5 /dev/sd[cde]
>> >
>> > $ mount /dev/sde /mnt/btrfs
>> >
>> > $ xfs_io -f -d -c "pwrite 0 128K" /mnt/btrfs/foobar
>> > wrote 131072/131072 bytes at offset 0
>> > 128 KiB, 32 ops; 0.0000 sec (5.842 MiB/sec and 1495.6766 ops/sec)
>> >
>> > $ od -t x1 /mnt/btrfs/foobar
>> > 0000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
>> > *
>> > 0400000
>> >
>> > $ uname -r
>> > 4.12.0+
>> >
>> > It works fine without causing 'generic protection' during mount.
>>
>> Yes, the trace was not from running the test mentioned in the
>> changelog, but rather btrfs/0[60-74] iirc or some other stress tests.
>> It doesn't happen always as well.
>>
>
> I see, then it might be caused by some other problems, as the trace
> shows, it's a buffered write whose bio is not cloned, so it still
> takes bio->bi_iter for the iteration.
>
> The 'general protection' was in finish_rmw(), could you please check
> if that points to somewhere inside this bio_for_each_segment() helper?

(gdb) list *(finish_rmw+0x1d6)
0x97eb4 is in finish_rmw (fs/btrfs/raid56.c:1252).
1247
1248 raid6_call.gen_syndrome(rbio->real_stripes, PAGE_SIZE,
1249 pointers);
1250 } else {
1251 /* raid5 */
1252 memcpy(pointers[nr_data], pointers[0], PAGE_SIZE);
1253 run_xor(pointers + 1, nr_data - 1, PAGE_SIZE);
1254 }
1255
1256

finish_rmw() does not call bio_for_each_segment nor any equivalent, so
it's the consequence of a previous call to one of those iterators,
such as at index_rbio_pages setting bio_pages[] with some invalid
memory address for example.

>
> thanks,
>
> -liubo
>
>> >
>> > thanks,
>> >
>> > -liubo
>> >
>> >> -liubo
>> >>
>> >> > [ 3955.729020] general protection fault: 0000 [#1] PREEMPT SMP
>> >> > [ 3955.729845] Modules linked in: btrfs ppdev tpm_tis evdev psmouse
>> >> > parport_pc sg tpm_tis_core i2c_piix4 parport tpm pcspkr serio_raw
>> >> > i2c_core button sunrpc loop auto
>> >> > fs4 ext4 crc16 jbd2 mbcache raid10 raid456 async_raid6_recov
>> >> > async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c
>> >> > crc32c_generic raid1 raid0 multipath line
>> >> > ar md_mod sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix libata
>> >> > virtio_pci virtio_ring scsi_mod virtio e1000 floppy [last unloaded:
>> >> > btrfs]
>> >> > [ 3955.731730] CPU: 15 PID: 26361 Comm: mount Not tainted
>> >> > 4.12.0-rc6-btrfs-next-47+ #1
>> >> > [ 3955.731730] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> >> > BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>> >> > [ 3955.731730] task: ffff880235b5d680 task.stack: ffffc90002498000
>> >> > [ 3955.731730] RIP: 0010:finish_rmw+0x1d6/0x3c4 [btrfs]
>> >> > [ 3955.731730] RSP: 0018:ffffc9000249b3d8 EFLAGS: 00010246
>> >> > [ 3955.731730] RAX: ffff880235e86000 RBX: ffff880210e23800 RCX: 0000000000000400
>> >> > [ 3955.731730] RDX: ffff880000000000 RSI: db73880000000000 RDI: ffff880235e86000
>> >> > [ 3955.731730] RBP: ffffc9000249b470 R08: 0000000000000001 R09: 0000000000000001
>> >> > [ 3955.731730] R10: ffffc9000249b310 R11: 0000000000000003 R12: ffffc9000249b3d8
>> >> > [ 3955.731730] R13: 0000000000000000 R14: 0000000000000003 R15: ffffc9000249b3f0
>> >> > [ 3955.731730] FS:  00007f68fda61480(0000) GS:ffff88023f5c0000(0000)
>> >> > knlGS:0000000000000000
>> >> > [ 3955.731730] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> >> > [ 3955.731730] CR2: 000056403c233680 CR3: 000000021049e000 CR4: 00000000000006e0
>> >> > [ 3955.731730] Call Trace:
>> >> > [ 3955.731730]  full_stripe_write+0x69/0x93 [btrfs]
>> >> > [ 3955.731730]  raid56_parity_write+0xa4/0x110 [btrfs]
>> >> > [ 3955.731730]  btrfs_map_bio+0xca/0x259 [btrfs]
>> >> > [ 3955.731730]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
>> >> > [ 3955.731730]  submit_one_bio+0x5d/0x7b [btrfs]
>> >> > [ 3955.731730]  submit_extent_page.constprop.30+0x99/0x165 [btrfs]
>> >> > [ 3955.731730]  ? __test_set_page_writeback+0x1aa/0x1bc
>> >> > [ 3955.731730]  __extent_writepage_io+0x328/0x3a2 [btrfs]
>> >> > [ 3955.731730]  ? end_extent_writepage+0xc4/0xc4 [btrfs]
>> >> > [ 3955.731730]  __extent_writepage+0x236/0x2bd [btrfs]
>> >> > [ 3955.731730]  extent_write_cache_pages.constprop.27+0x1ed/0x35e [btrfs]
>> >> > [ 3955.731730]  extent_writepages+0x4c/0x5d [btrfs]
>> >> > [ 3955.731730]  ? rcu_read_lock_sched_held+0x57/0x6c
>> >> > [ 3955.731730]  ? btrfs_set_bit_hook+0x233/0x233 [btrfs]
>> >> > [ 3955.731730]  ? __clear_extent_bit+0x2ab/0x2ca [btrfs]
>> >> > [ 3955.731730]  btrfs_writepages+0x28/0x2a [btrfs]
>> >> > [ 3955.731730]  do_writepages+0x3c/0x72
>> >> > [ 3955.731730]  __filemap_fdatawrite_range+0x5a/0x63
>> >> > [ 3955.731730]  filemap_fdatawrite_range+0x13/0x15
>> >> > [ 3955.731730]  btrfs_fdatawrite_range+0x20/0x46 [btrfs]
>> >> > [ 3955.731730]  __btrfs_write_out_cache+0x2db/0x3aa [btrfs]
>> >> > [ 3955.731730]  btrfs_write_out_cache+0x8a/0xcd [btrfs]
>> >> > [ 3955.731730]  btrfs_start_dirty_block_groups+0x190/0x394 [btrfs]
>> >> > [ 3955.731730]  btrfs_commit_transaction+0xdd/0x7d6 [btrfs]
>> >> > [ 3955.731730]  btrfs_create_uuid_tree+0xa3/0x10e [btrfs]
>> >> > [ 3955.731730]  open_ctree+0x1ed5/0x21b5 [btrfs]
>> >> > [ 3955.731730]  btrfs_mount+0x9b6/0xb14 [btrfs]
>> >> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
>> >> > [ 3955.731730]  mount_fs+0x67/0x114
>> >> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
>> >> > [ 3955.731730]  btrfs_mount+0x1a1/0xb14 [btrfs]
>> >> > [ 3955.731730]  ? trace_hardirqs_on_caller+0x150/0x1ac
>> >> > [ 3955.731730]  ? lockdep_init_map+0x17f/0x1d1
>> >> > [ 3955.731730]  mount_fs+0x67/0x114
>> >> > [ 3955.731730]  vfs_kern_mount+0x6b/0xdb
>> >> > [ 3955.731730]  do_mount+0x6e3/0x96d
>> >> > [ 3955.731730]  ? strndup_user+0x3f/0x73
>> >> > [ 3955.731730]  SyS_mount+0x77/0x9f
>> >> > [ 3955.731730]  entry_SYSCALL_64_fastpath+0x18/0xad
>> >> > [ 3955.731730] RIP: 0033:0x7f68fd12a0ba
>> >> > [ 3955.731730] RSP: 002b:00007fffa95cc358 EFLAGS: 00000202 ORIG_RAX:
>> >> > 00000000000000a5
>> >> > [ 3955.731730] RAX: ffffffffffffffda RBX: ffffffff81092dd9 RCX: 00007f68fd12a0ba
>> >> > [ 3955.731730] RDX: 000055abf6a10240 RSI: 000055abf6a10280 RDI: 000055abf6a10260
>> >> > [ 3955.731730] RBP: ffffc9000249bf98 R08: 0000000000000000 R09: 0000000000000020
>> >> > [ 3955.731730] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000000000000046
>> >> > [ 3955.731730] R13: ffffc9000249bf78 R14: 0000000000000000 R15: 00000000ffffffff
>> >> > [ 3955.731730]  ? trace_hardirqs_off_caller+0x3f/0xa3
>> >> > [ 3955.731730] Code: 01 00 00 49 89 47 08 4c 89 e2 be 00 10 00 00 ff
>> >> > 15 b9 a5 ef ff eb 37 48 8b 45 a0 49 8b 34 24 b9 00 04 00 00 49 8b 04
>> >> > c4 48 89 c7 <f3> a5 8b 75 9c 48 8b 7d 90 e8 16 f4 ff ff eb 13 8b 75 bc
>> >> > 31 c9
>> >> > [ 3955.731730] RIP: finish_rmw+0x1d6/0x3c4 [btrfs] RSP: ffffc9000249b3d8
>> >> > [ 3955.823152] ---[ end trace 5bf4b7e7b83f4313 ]---
>> >> >
>> >> >
>> >> > >
>> >> > >> +             bio_for_each_segment(bvec, bio, iter) {
>> >> > >> +                     rbio->bio_pages[page_index + i] = bvec.bv_page;
>> >> > >> +                     i++;
>> >> > >> +             }
>> >> > >>       }
>> >> > >>       spin_unlock_irq(&rbio->bio_list_lock);
>> >> > >>  }
>> >> > >> @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
>> >> > >>   */
>> >> > >>  static void set_bio_pages_uptodate(struct bio *bio)
>> >> > >>  {
>> >> > >> -     struct bio_vec *bvec;
>> >> > >> -     int i;
>> >> > >> +     struct bio_vec bvec;
>> >> > >> +     struct bvec_iter iter;
>> >> > >> +
>> >> > >> +     if (bio_flagged(bio, BIO_CLONED))
>> >> > >> +             bio->bi_iter = btrfs_io_bio(bio)->iter;
>> >> > >>
>> >> > >
>> >> > > Ditto.
>> >> > >
>> >> > > Others look good.
>> >> > >
>> >> > > Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
>> >> > >
>> >> > > -liubo
>> >> > >
>> >> > >> -     bio_for_each_segment_all(bvec, bio, i)
>> >> > >> -             SetPageUptodate(bvec->bv_page);
>> >> > >> +     bio_for_each_segment(bvec, bio, iter)
>> >> > >> +             SetPageUptodate(bvec.bv_page);
>> >> > >>  }
>> >> > >>
>> >> > >>  /*
>> >> > >> --
>> >> > >> 2.11.0
>> >> > >>
>> >> > >> --
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Filipe Manana July 14, 2017, 9:04 a.m. UTC | #10 
On Thu, Jul 13, 2017 at 11:38 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> On Thu, Jul 13, 2017 at 09:36:19AM -0700, Liu Bo wrote:
>> On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
>> > From: Filipe Manana <fdmanana@suse.com>
>> >
>> > The recent changes to make bio cloning faster (added in the 4.13 merge
>> > window) by using the bio_clone_fast() API introduced a regression on
>> > raid5/6 modes, because cloned bios have an invalid bi_vcnt field
>> > (therefore it can not be used) and the raid5/6 code uses the
>> > bio_for_each_segment_all() API to iterate the segments of a bio, and this
>> > API uses a bio's bi_vcnt field.
>> >
>> > The issue is very simple to trigger by doing for example a direct IO write
>> > against a raid5 or raid6 filesystem and then attempting to read what we
>> > wrote before:
>> >
>> >   $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
>> >   $ mount /dev/sdc /mnt
>> >   $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
>> >   $ od -t x1 /mnt/foobar
>> >   od: /mnt/foobar: read error: Input/output error
>> >
>> > For that example, the following is also reported in dmesg/syslog:
>> >
>> >   [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
>> >   [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
>> >   [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
>> >   [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >   [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
>> >
>> > A scrub will also fail correcting bad copies, mentioning the following in
>> > dmesg/syslog:
>> >
>> >   [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
>> >   [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
>> >   [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
>> >   [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>> >   [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
>> >   [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>> >   [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
>> >   [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>> >   [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
>> >   [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
>> >   [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
>> >   [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
>> >   [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
>> >   [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
>> >   [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>> >   [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
>> >   [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
>> >   [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
>> >   [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
>> >   [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
>> >   [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
>> >   [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
>> >   [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
>> >   [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
>> >   [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
>> >   [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
>> >   [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
>> >   [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde
>> >
>> > So fix this by using the bio_for_each_segment() API and setting before
>> > the bio's bi_iter field to the value of the corresponding btrfs bio
>> > container's saved iterator if we are processing a cloned bio in the
>> > raid5/6 code (the same code processes both cloned and non-cloned bios).
>> >
>> > This incorrect iteration of cloned bios was also causing some occasional
>> > BUG_ONs when running fstest btrfs/064, which have a trace like the
>> > following:
>> >
>> >   [ 6674.416156] ------------[ cut here ]------------
>> >   [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
>> >   [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
>> >   [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
>> >   [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
>> >   [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
>> >   [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
>> >   [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
>> >   [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
>> >   [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
>> >   [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
>> >   [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
>> >   [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
>> >   [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
>> >   [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
>> >   [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
>> >   [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> >   [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
>> >   [ 6674.416239] Call Trace:
>> >   [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
>> >   [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
>> >   [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
>> >   [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
>> >   [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
>> >   [ 6674.416331]  bio_endio+0x17d/0x1b3
>> >   [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
>> >   [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
>> >   [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
>> >   [ 6674.416381]  process_one_work+0x276/0x4b6
>> >   [ 6674.416384]  worker_thread+0x1ac/0x266
>> >   [ 6674.416386]  ? rescuer_thread+0x278/0x278
>> >   [ 6674.416387]  kthread+0x106/0x10e
>> >   [ 6674.416389]  ? __list_del_entry+0x22/0x22
>> >   [ 6674.416391]  ret_from_fork+0x27/0x40
>> >   [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
>> >   [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
>> >   [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---
>> >
>>
>> Thank you so much for the fix!
>>
>>
>> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
>> > ---
>> >  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
>> >  1 file changed, 18 insertions(+), 8 deletions(-)
>> >
>> > diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
>> > index b9abb0b01021..b89d07003697 100644
>> > --- a/fs/btrfs/raid56.c
>> > +++ b/fs/btrfs/raid56.c
>> > @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
>> >  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
>> >  {
>> >     struct bio *bio;
>> > -   struct bio_vec *bvec;
>> >     u64 start;
>> >     unsigned long stripe_offset;
>> >     unsigned long page_index;
>> > -   int i;
>> >
>> >     spin_lock_irq(&rbio->bio_list_lock);
>> >     bio_list_for_each(bio, &rbio->bio_list) {
>> > +           struct bio_vec bvec;
>> > +           struct bvec_iter iter;
>> > +           int i = 0;
>> > +
>> >             start = (u64)bio->bi_iter.bi_sector << 9;
>> >             stripe_offset = start - rbio->bbio->raid_map[0];
>> >             page_index = stripe_offset >> PAGE_SHIFT;
>> >
>> > -           bio_for_each_segment_all(bvec, bio, i)
>> > -                   rbio->bio_pages[page_index + i] = bvec->bv_page;
>> > +           if (bio_flagged(bio, BIO_CLONED))
>> > +                   bio->bi_iter = btrfs_io_bio(bio)->iter;
>> > +
>>
>> I think we can use use bio->bi_iter directly as the bio is not
>> submitted yet, i.e. bi_iter is not advanced yet.
>>
>> > +           bio_for_each_segment(bvec, bio, iter) {
>> > +                   rbio->bio_pages[page_index + i] = bvec.bv_page;
>> > +                   i++;
>> > +           }
>> >     }
>> >     spin_unlock_irq(&rbio->bio_list_lock);
>> >  }
>> > @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
>> >   */
>> >  static void set_bio_pages_uptodate(struct bio *bio)
>> >  {
>> > -   struct bio_vec *bvec;
>> > -   int i;
>> > +   struct bio_vec bvec;
>> > +   struct bvec_iter iter;
>> > +
>> > +   if (bio_flagged(bio, BIO_CLONED))
>> > +           bio->bi_iter = btrfs_io_bio(bio)->iter;
>> >
>
> It is not necessary to update set_bio_pages_uptodate() because the bio
> here is for reading pages in RMW and no way it could be a cloned one.

From my testing I've never seen this function getting cloned bios as
well. But I'm afraid we don't have full test coverage and it scares me
to have code around that can cause silent corruptions or crashes due
to such subtle details (bi_vcnt can't be used for cloned bios and it's
not obvious which APIs from the block layer make use of it without
reading their code). Plus a quick look I had at btrfs_map_bio()
suggested it can clone bios used for read operations through
btrfs_submit_bio_hook() for example. So that's why I changed that
function too to be able to deal both with cloned and non-cloned bios.

>
> thanks,
>
> -liubo
>
>>
>> Ditto.
>>
>> Others look good.
>>
>> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
>>
>> -liubo
>>
>> > -   bio_for_each_segment_all(bvec, bio, i)
>> > -           SetPageUptodate(bvec->bv_page);
>> > +   bio_for_each_segment(bvec, bio, iter)
>> > +           SetPageUptodate(bvec.bv_page);
>> >  }
>> >
>> >  /*
>> > --
>> > 2.11.0
>> >
>> > --
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>> > the body of a message to majordomo@vger.kernel.org
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>> --
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David Sterba July 14, 2017, 12:45 p.m. UTC | #11 
On Fri, Jul 14, 2017 at 10:04:34AM +0100, Filipe Manana wrote:
> On Thu, Jul 13, 2017 at 11:38 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> > On Thu, Jul 13, 2017 at 09:36:19AM -0700, Liu Bo wrote:
> >> On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> >> > @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> >> >   */
> >> >  static void set_bio_pages_uptodate(struct bio *bio)
> >> >  {
> >> > -   struct bio_vec *bvec;
> >> > -   int i;
> >> > +   struct bio_vec bvec;
> >> > +   struct bvec_iter iter;
> >> > +
> >> > +   if (bio_flagged(bio, BIO_CLONED))
> >> > +           bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> >
> >
> > It is not necessary to update set_bio_pages_uptodate() because the bio
> > here is for reading pages in RMW and no way it could be a cloned one.
> 
> >From my testing I've never seen this function getting cloned bios as
> well. But I'm afraid we don't have full test coverage and it scares me
> to have code around that can cause silent corruptions or crashes due
> to such subtle details (bi_vcnt can't be used for cloned bios and it's
> not obvious which APIs from the block layer make use of it without
> reading their code). Plus a quick look I had at btrfs_map_bio()
> suggested it can clone bios used for read operations through
> btrfs_submit_bio_hook() for example. So that's why I changed that
> function too to be able to deal both with cloned and non-cloned bios.

I agree with that approach. My first reaction was to switch to
bio_for_each_segment everywhere, but this would increase stack
consumption by 32 bytes, so with the asserts in place I hope we'd catch
potential cloned/bi_vcnt violations. As you point out, the API is not
clear on that.
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Liu Bo July 14, 2017, 4:56 p.m. UTC | #12 
On Fri, Jul 14, 2017 at 10:04:34AM +0100, Filipe Manana wrote:
> On Thu, Jul 13, 2017 at 11:38 PM, Liu Bo <bo.li.liu@oracle.com> wrote:
> > On Thu, Jul 13, 2017 at 09:36:19AM -0700, Liu Bo wrote:
> >> On Thu, Jul 13, 2017 at 03:09:54PM +0100, fdmanana@kernel.org wrote:
> >> > From: Filipe Manana <fdmanana@suse.com>
> >> >
> >> > The recent changes to make bio cloning faster (added in the 4.13 merge
> >> > window) by using the bio_clone_fast() API introduced a regression on
> >> > raid5/6 modes, because cloned bios have an invalid bi_vcnt field
> >> > (therefore it can not be used) and the raid5/6 code uses the
> >> > bio_for_each_segment_all() API to iterate the segments of a bio, and this
> >> > API uses a bio's bi_vcnt field.
> >> >
> >> > The issue is very simple to trigger by doing for example a direct IO write
> >> > against a raid5 or raid6 filesystem and then attempting to read what we
> >> > wrote before:
> >> >
> >> >   $ mkfs.btrfs -m raid5 -d raid5 -f /dev/sdc /dev/sdd /dev/sde /dev/sdf
> >> >   $ mount /dev/sdc /mnt
> >> >   $ xfs_io -f -d -c "pwrite -S 0xab 0 1M" /mnt/foobar
> >> >   $ od -t x1 /mnt/foobar
> >> >   od: /mnt/foobar: read error: Input/output error
> >> >
> >> > For that example, the following is also reported in dmesg/syslog:
> >> >
> >> >   [18274.985557] btrfs_print_data_csum_error: 18 callbacks suppressed
> >> >   [18274.995277] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18274.997205] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.025221] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.047422] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.054818] BTRFS warning (device sdf): csum failed root 5 ino 257 off 4096 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.054834] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.054943] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 2
> >> >   [18275.055207] BTRFS warning (device sdf): csum failed root 5 ino 257 off 8192 csum 0x98f94189 expected csum 0x94374193 mirror 3
> >> >   [18275.055571] BTRFS warning (device sdf): csum failed root 5 ino 257 off 0 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >   [18275.062171] BTRFS warning (device sdf): csum failed root 5 ino 257 off 12288 csum 0x98f94189 expected csum 0x94374193 mirror 1
> >> >
> >> > A scrub will also fail correcting bad copies, mentioning the following in
> >> > dmesg/syslog:
> >> >
> >> >   [18276.128696] scrub_handle_errored_block: 498 callbacks suppressed
> >> >   [18276.129617] BTRFS warning (device sdf): checksum error at logical 2186346496 on dev /dev/sde, sector 2116608, root 5, inode 257, offset 65536, length 4096, links $
> >> >   [18276.149235] btrfs_dev_stat_print_on_error: 498 callbacks suppressed
> >> >   [18276.157897] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >> >   [18276.206059] BTRFS warning (device sdf): checksum error at logical 2186477568 on dev /dev/sdd, sector 2116736, root 5, inode 257, offset 196608, length 4096, links$
> >> >   [18276.206059] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >> >   [18276.306552] BTRFS warning (device sdf): checksum error at logical 2186543104 on dev /dev/sdd, sector 2116864, root 5, inode 257, offset 262144, length 4096, links$
> >> >   [18276.319152] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
> >> >   [18276.394316] BTRFS warning (device sdf): checksum error at logical 2186739712 on dev /dev/sdf, sector 2116992, root 5, inode 257, offset 458752, length 4096, links$
> >> >   [18276.396348] BTRFS error (device sdf): bdev /dev/sdf errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
> >> >   [18276.434127] BTRFS warning (device sdf): checksum error at logical 2186870784 on dev /dev/sde, sector 2117120, root 5, inode 257, offset 589824, length 4096, links$
> >> >   [18276.434127] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
> >> >   [18276.500504] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186477568 on dev /dev/sdd
> >> >   [18276.538400] BTRFS warning (device sdf): checksum error at logical 2186481664 on dev /dev/sdd, sector 2116744, root 5, inode 257, offset 200704, length 4096, links$
> >> >   [18276.540452] BTRFS error (device sdf): bdev /dev/sdd errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
> >> >   [18276.542012] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186481664 on dev /dev/sdd
> >> >   [18276.585030] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186346496 on dev /dev/sde
> >> >   [18276.598306] BTRFS warning (device sdf): checksum error at logical 2186412032 on dev /dev/sde, sector 2116736, root 5, inode 257, offset 131072, length 4096, links$
> >> >   [18276.598310] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 3, gen 0
> >> >   [18276.598582] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186350592 on dev /dev/sde
> >> >   [18276.603455] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 4, gen 0
> >> >   [18276.638362] BTRFS warning (device sdf): checksum error at logical 2186354688 on dev /dev/sde, sector 2116624, root 5, inode 257, offset 73728, length 4096, links $
> >> >   [18276.640445] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 5, gen 0
> >> >   [18276.645942] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186354688 on dev /dev/sde
> >> >   [18276.657204] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186412032 on dev /dev/sde
> >> >   [18276.660563] BTRFS warning (device sdf): checksum error at logical 2186416128 on dev /dev/sde, sector 2116744, root 5, inode 257, offset 135168, length 4096, links$
> >> >   [18276.664609] BTRFS error (device sdf): bdev /dev/sde errs: wr 0, rd 0, flush 0, corrupt 6, gen 0
> >> >   [18276.664609] BTRFS error (device sdf): unable to fixup (regular) error at logical 2186358784 on dev /dev/sde
> >> >
> >> > So fix this by using the bio_for_each_segment() API and setting before
> >> > the bio's bi_iter field to the value of the corresponding btrfs bio
> >> > container's saved iterator if we are processing a cloned bio in the
> >> > raid5/6 code (the same code processes both cloned and non-cloned bios).
> >> >
> >> > This incorrect iteration of cloned bios was also causing some occasional
> >> > BUG_ONs when running fstest btrfs/064, which have a trace like the
> >> > following:
> >> >
> >> >   [ 6674.416156] ------------[ cut here ]------------
> >> >   [ 6674.416157] kernel BUG at fs/btrfs/raid56.c:1897!
> >> >   [ 6674.416159] invalid opcode: 0000 [#1] PREEMPT SMP
> >> >   [ 6674.416160] Modules linked in: dm_flakey dm_mod dax ppdev tpm_tis parport_pc tpm_tis_core evdev tpm psmouse sg i2c_piix4 pcspkr parport i2c_core serio_raw button s
> >> >   [ 6674.416184] CPU: 3 PID: 19236 Comm: kworker/u32:10 Not tainted 4.12.0-rc6-btrfs-next-44+ #1
> >> >   [ 6674.416185] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
> >> >   [ 6674.416210] Workqueue: btrfs-endio btrfs_endio_helper [btrfs]
> >> >   [ 6674.416211] task: ffff880147f6c740 task.stack: ffffc90001fb8000
> >> >   [ 6674.416229] RIP: 0010:__raid_recover_end_io+0x1ac/0x370 [btrfs]
> >> >   [ 6674.416230] RSP: 0018:ffffc90001fbbb90 EFLAGS: 00010217
> >> >   [ 6674.416231] RAX: ffff8801ff4b4f00 RBX: 0000000000000002 RCX: 0000000000000001
> >> >   [ 6674.416232] RDX: ffff880099b045d8 RSI: ffffffff81a5f6e0 RDI: 0000000000000004
> >> >   [ 6674.416232] RBP: ffffc90001fbbbc8 R08: 0000000000000001 R09: 0000000000000001
> >> >   [ 6674.416233] R10: ffffc90001fbbac8 R11: 0000000000001000 R12: 0000000000000002
> >> >   [ 6674.416234] R13: ffff880099b045c0 R14: 0000000000000004 R15: ffff88012bff2000
> >> >   [ 6674.416235] FS:  0000000000000000(0000) GS:ffff88023f2c0000(0000) knlGS:0000000000000000
> >> >   [ 6674.416235] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> >   [ 6674.416236] CR2: 00007f28cf282000 CR3: 00000001000c6000 CR4: 00000000000006e0
> >> >   [ 6674.416239] Call Trace:
> >> >   [ 6674.416259]  __raid56_parity_recover+0xfc/0x16e [btrfs]
> >> >   [ 6674.416276]  raid56_parity_recover+0x157/0x16b [btrfs]
> >> >   [ 6674.416293]  btrfs_map_bio+0xe0/0x259 [btrfs]
> >> >   [ 6674.416310]  btrfs_submit_bio_hook+0xbf/0x147 [btrfs]
> >> >   [ 6674.416327]  end_bio_extent_readpage+0x27b/0x4a0 [btrfs]
> >> >   [ 6674.416331]  bio_endio+0x17d/0x1b3
> >> >   [ 6674.416346]  end_workqueue_fn+0x3c/0x3f [btrfs]
> >> >   [ 6674.416362]  btrfs_scrubparity_helper+0x1aa/0x3b8 [btrfs]
> >> >   [ 6674.416379]  btrfs_endio_helper+0xe/0x10 [btrfs]
> >> >   [ 6674.416381]  process_one_work+0x276/0x4b6
> >> >   [ 6674.416384]  worker_thread+0x1ac/0x266
> >> >   [ 6674.416386]  ? rescuer_thread+0x278/0x278
> >> >   [ 6674.416387]  kthread+0x106/0x10e
> >> >   [ 6674.416389]  ? __list_del_entry+0x22/0x22
> >> >   [ 6674.416391]  ret_from_fork+0x27/0x40
> >> >   [ 6674.416395] Code: 44 89 e2 be 00 10 00 00 ff 15 b0 ab ef ff eb 72 4d 89 e8 89 d9 44 89 e2 be 00 10 00 00 ff 15 a3 ab ef ff eb 5d 41 83 fc ff 74 02 <0f> 0b 49 63 97
> >> >   [ 6674.416432] RIP: __raid_recover_end_io+0x1ac/0x370 [btrfs] RSP: ffffc90001fbbb90
> >> >   [ 6674.416434] ---[ end trace 74d56ebe7489dd6a ]---
> >> >
> >>
> >> Thank you so much for the fix!
> >>
> >>
> >> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> >> > ---
> >> >  fs/btrfs/raid56.c | 26 ++++++++++++++++++--------
> >> >  1 file changed, 18 insertions(+), 8 deletions(-)
> >> >
> >> > diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> >> > index b9abb0b01021..b89d07003697 100644
> >> > --- a/fs/btrfs/raid56.c
> >> > +++ b/fs/btrfs/raid56.c
> >> > @@ -1136,20 +1136,27 @@ static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
> >> >  static void index_rbio_pages(struct btrfs_raid_bio *rbio)
> >> >  {
> >> >     struct bio *bio;
> >> > -   struct bio_vec *bvec;
> >> >     u64 start;
> >> >     unsigned long stripe_offset;
> >> >     unsigned long page_index;
> >> > -   int i;
> >> >
> >> >     spin_lock_irq(&rbio->bio_list_lock);
> >> >     bio_list_for_each(bio, &rbio->bio_list) {
> >> > +           struct bio_vec bvec;
> >> > +           struct bvec_iter iter;
> >> > +           int i = 0;
> >> > +
> >> >             start = (u64)bio->bi_iter.bi_sector << 9;
> >> >             stripe_offset = start - rbio->bbio->raid_map[0];
> >> >             page_index = stripe_offset >> PAGE_SHIFT;
> >> >
> >> > -           bio_for_each_segment_all(bvec, bio, i)
> >> > -                   rbio->bio_pages[page_index + i] = bvec->bv_page;
> >> > +           if (bio_flagged(bio, BIO_CLONED))
> >> > +                   bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> > +
> >>
> >> I think we can use use bio->bi_iter directly as the bio is not
> >> submitted yet, i.e. bi_iter is not advanced yet.
> >>
> >> > +           bio_for_each_segment(bvec, bio, iter) {
> >> > +                   rbio->bio_pages[page_index + i] = bvec.bv_page;
> >> > +                   i++;
> >> > +           }
> >> >     }
> >> >     spin_unlock_irq(&rbio->bio_list_lock);
> >> >  }
> >> > @@ -1423,11 +1430,14 @@ static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
> >> >   */
> >> >  static void set_bio_pages_uptodate(struct bio *bio)
> >> >  {
> >> > -   struct bio_vec *bvec;
> >> > -   int i;
> >> > +   struct bio_vec bvec;
> >> > +   struct bvec_iter iter;
> >> > +
> >> > +   if (bio_flagged(bio, BIO_CLONED))
> >> > +           bio->bi_iter = btrfs_io_bio(bio)->iter;
> >> >
> >
> > It is not necessary to update set_bio_pages_uptodate() because the bio
> > here is for reading pages in RMW and no way it could be a cloned one.
> 
> From my testing I've never seen this function getting cloned bios as
> well. But I'm afraid we don't have full test coverage and it scares me
> to have code around that can cause silent corruptions or crashes due
> to such subtle details (bi_vcnt can't be used for cloned bios and it's
> not obvious which APIs from the block layer make use of it without
> reading their code). Plus a quick look I had at btrfs_map_bio()
> suggested it can clone bios used for read operations through
> btrfs_submit_bio_hook() for example. So that's why I changed that
> function too to be able to deal both with cloned and non-cloned bios.
>

Thanks for putting the explanation.  I'm OK with setting an extra
fence.

(Just to clarify it, unlike writes, reads on raid56 will read data
directly from disk, so it doesn't make difference whether it's cloned
or not.  For read retry, it adds the page to a newly created bio, so
it's not a cloned, either.)

thanks,
-liubo

> >
> > thanks,
> >
> > -liubo
> >
> >>
> >> Ditto.
> >>
> >> Others look good.
> >>
> >> Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
> >>
> >> -liubo
> >>
> >> > -   bio_for_each_segment_all(bvec, bio, i)
> >> > -           SetPageUptodate(bvec->bv_page);
> >> > +   bio_for_each_segment(bvec, bio, iter)
> >> > +           SetPageUptodate(bvec.bv_page);
> >> >  }
> >> >
> >> >  /*
> >> > --
> >> > 2.11.0
> >> >
> >> > --
> >> > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> >> > the body of a message to majordomo@vger.kernel.org
> >> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> >> the body of a message to majordomo@vger.kernel.org
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diff mbox

Patch

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index b9abb0b01021..b89d07003697 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1136,20 +1136,27 @@  static void validate_rbio_for_rmw(struct btrfs_raid_bio *rbio)
 static void index_rbio_pages(struct btrfs_raid_bio *rbio)
 {
 	struct bio *bio;
-	struct bio_vec *bvec;
 	u64 start;
 	unsigned long stripe_offset;
 	unsigned long page_index;
-	int i;
 
 	spin_lock_irq(&rbio->bio_list_lock);
 	bio_list_for_each(bio, &rbio->bio_list) {
+		struct bio_vec bvec;
+		struct bvec_iter iter;
+		int i = 0;
+
 		start = (u64)bio->bi_iter.bi_sector << 9;
 		stripe_offset = start - rbio->bbio->raid_map[0];
 		page_index = stripe_offset >> PAGE_SHIFT;
 
-		bio_for_each_segment_all(bvec, bio, i)
-			rbio->bio_pages[page_index + i] = bvec->bv_page;
+		if (bio_flagged(bio, BIO_CLONED))
+			bio->bi_iter = btrfs_io_bio(bio)->iter;
+
+		bio_for_each_segment(bvec, bio, iter) {
+			rbio->bio_pages[page_index + i] = bvec.bv_page;
+			i++;
+		}
 	}
 	spin_unlock_irq(&rbio->bio_list_lock);
 }
@@ -1423,11 +1430,14 @@  static int fail_bio_stripe(struct btrfs_raid_bio *rbio,
  */
 static void set_bio_pages_uptodate(struct bio *bio)
 {
-	struct bio_vec *bvec;
-	int i;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+
+	if (bio_flagged(bio, BIO_CLONED))
+		bio->bi_iter = btrfs_io_bio(bio)->iter;
 
-	bio_for_each_segment_all(bvec, bio, i)
-		SetPageUptodate(bvec->bv_page);
+	bio_for_each_segment(bvec, bio, iter)
+		SetPageUptodate(bvec.bv_page);
 }
 
 /*