| Message ID | 1d4f72f7fee285b2ddf4bf62b0ac0fd89def5417.1728575379.git.naohiro.aota@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] btrfs: fix error propagation of split bios | expand |
在 2024/10/11 02:27, Naohiro Aota 写道: > The purpose of btrfs_bbio_propagate_error() shall be propagating an error > of split bio to its original btrfs_bio, and tell the error to the upper > layer. However, it's not working well on some cases. > > * Case 1. Immediate (or quick) end_bio with an error > > When btrfs sends btrfs_bio to mirrored devices, btrfs calls > btrfs_bio_end_io() when all the mirroring bios are completed. If that > btrfs_bio was split, it is from btrfs_clone_bioset and its end_io function > is btrfs_orig_write_end_io. For this case, btrfs_bbio_propagate_error() > accesses the orig_bbio's bio context to increase the error count. > > That works well in most cases. However, if the end_io is called enough > fast, orig_bbio's (remaining part after split) bio context may not be > properly set at that time. Since the bio context is set when the orig_bbio > (the last btrfs_bio) is sent to devices, that might be too late for earlier > split btrfs_bio's completion. That will result in NULL pointer > dereference. > > That bug is easily reproducible by running btrfs/146 on zoned devices [1] > and it shows the following trace. > > [1] You need raid-stripe-tree feature as it create "-d raid0 -m raid1" FS. > > [ 20.923980][ T13] BUG: kernel NULL pointer dereference, address: 0000000000000020 > [ 20.925234][ T13] #PF: supervisor read access in kernel mode > [ 20.926122][ T13] #PF: error_code(0x0000) - not-present page > [ 20.927118][ T13] PGD 0 P4D 0 > [ 20.927607][ T13] Oops: Oops: 0000 [#1] PREEMPT SMP PTI > [ 20.928424][ T13] CPU: 1 UID: 0 PID: 13 Comm: kworker/u32:1 Not tainted 6.11.0-rc7-BTRFS-ZNS+ #474 > [ 20.929740][ T13] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 20.930697][ T13] Workqueue: writeback wb_workfn (flush-btrfs-5) > [ 20.931643][ T13] RIP: 0010:btrfs_bio_end_io+0xae/0xc0 [btrfs] > [ 20.932573][ T1415] BTRFS error (device dm-0): bdev /dev/mapper/error-test errs: wr 2, rd 0, flush 0, corrupt 0, gen 0 > [ 20.932871][ T13] Code: ba e1 48 8b 7b 10 e8 f1 f5 f6 ff eb da 48 81 bf 10 01 00 00 40 0c 33 a0 74 09 40 88 b5 f1 00 00 00 eb b8 48 8b 85 18 01 00 00 <48> 8b 40 20 0f b7 50 24 f0 01 50 20 eb a3 0f 1f 40 00 90 90 90 90 > [ 20.936623][ T13] RSP: 0018:ffffc9000006f248 EFLAGS: 00010246 > [ 20.937543][ T13] RAX: 0000000000000000 RBX: ffff888005a7f080 RCX: ffffc9000006f1dc > [ 20.938788][ T13] RDX: 0000000000000000 RSI: 000000000000000a RDI: ffff888005a7f080 > [ 20.940016][ T13] RBP: ffff888011dfc540 R08: 0000000000000000 R09: 0000000000000001 > [ 20.941227][ T13] R10: ffffffff82e508e0 R11: 0000000000000005 R12: ffff88800ddfbe58 > [ 20.942375][ T13] R13: ffff888005a7f080 R14: ffff888005a7f158 R15: ffff888005a7f158 > [ 20.943531][ T13] FS: 0000000000000000(0000) GS:ffff88803ea80000(0000) knlGS:0000000000000000 > [ 20.944838][ T13] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 20.945811][ T13] CR2: 0000000000000020 CR3: 0000000002e22006 CR4: 0000000000370ef0 > [ 20.946984][ T13] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 20.948150][ T13] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 20.949327][ T13] Call Trace: > [ 20.949949][ T13] <TASK> > [ 20.950374][ T13] ? __die_body.cold+0x19/0x26 > [ 20.951066][ T13] ? page_fault_oops+0x13e/0x2b0 > [ 20.951766][ T13] ? _printk+0x58/0x73 > [ 20.952358][ T13] ? do_user_addr_fault+0x5f/0x750 > [ 20.953120][ T13] ? exc_page_fault+0x76/0x240 > [ 20.953827][ T13] ? asm_exc_page_fault+0x22/0x30 > [ 20.954606][ T13] ? btrfs_bio_end_io+0xae/0xc0 [btrfs] > [ 20.955616][ T13] ? btrfs_log_dev_io_error+0x7f/0x90 [btrfs] > [ 20.956682][ T13] btrfs_orig_write_end_io+0x51/0x90 [btrfs] > [ 20.957769][ T13] dm_submit_bio+0x5c2/0xa50 [dm_mod] > [ 20.958623][ T13] ? find_held_lock+0x2b/0x80 > [ 20.959339][ T13] ? blk_try_enter_queue+0x90/0x1e0 > [ 20.960228][ T13] __submit_bio+0xe0/0x130 > [ 20.960879][ T13] ? ktime_get+0x10a/0x160 > [ 20.961546][ T13] ? lockdep_hardirqs_on+0x74/0x100 > [ 20.962310][ T13] submit_bio_noacct_nocheck+0x199/0x410 > [ 20.963140][ T13] btrfs_submit_bio+0x7d/0x150 [btrfs] > [ 20.964089][ T13] btrfs_submit_chunk+0x1a1/0x6d0 [btrfs] > [ 20.965066][ T13] ? lockdep_hardirqs_on+0x74/0x100 > [ 20.965824][ T13] ? __folio_start_writeback+0x10/0x2c0 > [ 20.966659][ T13] btrfs_submit_bbio+0x1c/0x40 [btrfs] > [ 20.967617][ T13] submit_one_bio+0x44/0x60 [btrfs] > [ 20.968536][ T13] submit_extent_folio+0x13f/0x330 [btrfs] > [ 20.969552][ T13] ? btrfs_set_range_writeback+0xa3/0xd0 [btrfs] > [ 20.970625][ T13] extent_writepage_io+0x18b/0x360 [btrfs] > [ 20.971632][ T13] extent_write_locked_range+0x17c/0x340 [btrfs] > [ 20.972702][ T13] ? __pfx_end_bbio_data_write+0x10/0x10 [btrfs] > [ 20.973857][ T13] run_delalloc_cow+0x71/0xd0 [btrfs] > [ 20.974841][ T13] btrfs_run_delalloc_range+0x176/0x500 [btrfs] > [ 20.975870][ T13] ? find_lock_delalloc_range+0x119/0x260 [btrfs] > [ 20.976911][ T13] writepage_delalloc+0x2ab/0x480 [btrfs] > [ 20.977792][ T13] extent_write_cache_pages+0x236/0x7d0 [btrfs] > [ 20.978728][ T13] btrfs_writepages+0x72/0x130 [btrfs] > [ 20.979531][ T13] do_writepages+0xd4/0x240 > [ 20.980111][ T13] ? find_held_lock+0x2b/0x80 > [ 20.980695][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 > [ 20.981461][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 > [ 20.982213][ T13] __writeback_single_inode+0x5c/0x4c0 > [ 20.982859][ T13] ? do_raw_spin_unlock+0x49/0xb0 > [ 20.983439][ T13] writeback_sb_inodes+0x22c/0x560 > [ 20.984079][ T13] __writeback_inodes_wb+0x4c/0xe0 > [ 20.984886][ T13] wb_writeback+0x1d6/0x3f0 > [ 20.985536][ T13] wb_workfn+0x334/0x520 > [ 20.986044][ T13] process_one_work+0x1ee/0x570 > [ 20.986580][ T13] ? lock_is_held_type+0xc6/0x130 > [ 20.987142][ T13] worker_thread+0x1d1/0x3b0 > [ 20.987918][ T13] ? __pfx_worker_thread+0x10/0x10 > [ 20.988690][ T13] kthread+0xee/0x120 > [ 20.989180][ T13] ? __pfx_kthread+0x10/0x10 > [ 20.989915][ T13] ret_from_fork+0x30/0x50 > [ 20.990615][ T13] ? __pfx_kthread+0x10/0x10 > [ 20.991336][ T13] ret_from_fork_asm+0x1a/0x30 > [ 20.992106][ T13] </TASK> > [ 20.992482][ T13] Modules linked in: dm_mod btrfs blake2b_generic xor raid6_pq rapl > [ 20.993406][ T13] CR2: 0000000000000020 > [ 20.993884][ T13] ---[ end trace 0000000000000000 ]--- > [ 20.993954][ T1415] BUG: kernel NULL pointer dereference, address: 0000000000000020 > > * Case 2. Earlier completion of orig_bbio for mirrored btrfs_bios > > btrfs_bbio_propagate_error() assumes the end_io function for orig_bbio is > called last among split bios. In that case, btrfs_orig_write_end_io() sets > the bio->bi_status to BLK_STS_IOERR by seeing the bioc->error [2]. > Otherwise, the increased orig_bio's bioc->error is not checked by anyone > and return BLK_STS_OK to the upper layer. > > [2] Actually, this is not true. Because we only increases orig_bioc->errors > by max_errors, the condition "atomic_read(&bioc->error) > bioc->max_errors" > is still not met if only one split btrfs_bio fails. > > * Case 3. Later completion of orig_bbio for un-mirrored btrfs_bios > > In contrast to the above case, btrfs_bbio_propagate_error() is not working > well if un-mirrored orig_bbio is completed last. It sets > orig_bbio->bio.bi_status to the btrfs_bio's error. But, that is easily > over-written by orig_bbio's completion status. If the status is BLK_STS_OK, > the upper layer would not know the failure. > > * Solution > > Considering the above cases, we can only save the error status in the > orig_bbio (remaining part after split) itself as it is always > available. Also, the saved error status should be propagated when all the > split btrfs_bios are finished (i.e, bbio->pending_ios == 0). > > This commit introduces "status" to btrfs_bbio and saves the first error of > split bios to original btrfs_bio's "status" variable. When all the split > bios are finished, the saved status is loaded into original btrfs_bio's > status. > > With this commit, btrfs/146 on zoned devices does not hit the NULL pointer > dereference. > > Fixes: 852eee62d31a ("btrfs: allow btrfs_submit_bio to split bios") > CC: stable@vger.kernel.org # 6.6+ > Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Thanks, Qu > --- > - v1: https://lore.kernel.org/linux-btrfs/db5c272fc27c59ddded5c691373c26458698cb1a.1728489285.git.naohiro.aota@wdc.com/ > - v2 > - Replace atomic_t usage to blk_status_t and cmpxchg() > --- > fs/btrfs/bio.c | 36 ++++++++++++------------------------ > fs/btrfs/bio.h | 3 +++ > 2 files changed, 15 insertions(+), 24 deletions(-) > > diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c > index 056f8a171bba..af12b23c8531 100644 > --- a/fs/btrfs/bio.c > +++ b/fs/btrfs/bio.c > @@ -49,6 +49,7 @@ void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_fs_info *fs_info, > bbio->end_io = end_io; > bbio->private = private; > atomic_set(&bbio->pending_ios, 1); > + WRITE_ONCE(bbio->status, BLK_STS_OK); > } > > /* > @@ -120,41 +121,28 @@ static void __btrfs_bio_end_io(struct btrfs_bio *bbio) > } > } > > -static void btrfs_orig_write_end_io(struct bio *bio); > - > -static void btrfs_bbio_propagate_error(struct btrfs_bio *bbio, > - struct btrfs_bio *orig_bbio) > -{ > - /* > - * For writes we tolerate nr_mirrors - 1 write failures, so we can't > - * just blindly propagate a write failure here. Instead increment the > - * error count in the original I/O context so that it is guaranteed to > - * be larger than the error tolerance. > - */ > - if (bbio->bio.bi_end_io == &btrfs_orig_write_end_io) { > - struct btrfs_io_stripe *orig_stripe = orig_bbio->bio.bi_private; > - struct btrfs_io_context *orig_bioc = orig_stripe->bioc; > - > - atomic_add(orig_bioc->max_errors, &orig_bioc->error); > - } else { > - orig_bbio->bio.bi_status = bbio->bio.bi_status; > - } > -} > - > void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status) > { > bbio->bio.bi_status = status; > if (bbio->bio.bi_pool == &btrfs_clone_bioset) { > struct btrfs_bio *orig_bbio = bbio->private; > > - if (bbio->bio.bi_status) > - btrfs_bbio_propagate_error(bbio, orig_bbio); > btrfs_cleanup_bio(bbio); > bbio = orig_bbio; > } > > - if (atomic_dec_and_test(&bbio->pending_ios)) > + /* At this point, bbio always points to the original btrfs_bio. Save the > + * first error in it. > + */ > + if (status != BLK_STS_OK) > + cmpxchg(&bbio->status, BLK_STS_OK, status); > + > + if (atomic_dec_and_test(&bbio->pending_ios)) { > + /* Load split bio's error which might be set above. */ > + if (status == BLK_STS_OK) > + bbio->bio.bi_status = READ_ONCE(bbio->status); > __btrfs_bio_end_io(bbio); > + } > } > > static int next_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror) > diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h > index e48612340745..566c3e1d077b 100644 > --- a/fs/btrfs/bio.h > +++ b/fs/btrfs/bio.h > @@ -79,6 +79,9 @@ struct btrfs_bio { > /* File system that this I/O operates on. */ > struct btrfs_fs_info *fs_info; > > + /* Set the error status of split bio. */ > + blk_status_t status; > + > /* > * This member must come last, bio_alloc_bioset will allocate enough > * bytes for entire btrfs_bio but relies on bio being last.
Looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
On 10.10.24 17:58, Naohiro Aota wrote: > > [ 20.923980][ T13] BUG: kernel NULL pointer dereference, address: 0000000000000020 > [ 20.925234][ T13] #PF: supervisor read access in kernel mode > [ 20.926122][ T13] #PF: error_code(0x0000) - not-present page > [ 20.927118][ T13] PGD 0 P4D 0 > [ 20.927607][ T13] Oops: Oops: 0000 [#1] PREEMPT SMP PTI > [ 20.928424][ T13] CPU: 1 UID: 0 PID: 13 Comm: kworker/u32:1 Not tainted 6.11.0-rc7-BTRFS-ZNS+ #474 > [ 20.929740][ T13] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 20.930697][ T13] Workqueue: writeback wb_workfn (flush-btrfs-5) > [ 20.931643][ T13] RIP: 0010:btrfs_bio_end_io+0xae/0xc0 [btrfs] > [ 20.932573][ T1415] BTRFS error (device dm-0): bdev /dev/mapper/error-test errs: wr 2, rd 0, flush 0, corrupt 0, gen 0 > [ 20.932871][ T13] Code: ba e1 48 8b 7b 10 e8 f1 f5 f6 ff eb da 48 81 bf 10 01 00 00 40 0c 33 a0 74 09 40 88 b5 f1 00 00 00 eb b8 48 8b 85 18 01 00 00 <48> 8b 40 20 0f b7 50 24 f0 01 50 20 eb a3 0f 1f 40 00 90 90 90 90 > [ 20.936623][ T13] RSP: 0018:ffffc9000006f248 EFLAGS: 00010246 > [ 20.937543][ T13] RAX: 0000000000000000 RBX: ffff888005a7f080 RCX: ffffc9000006f1dc > [ 20.938788][ T13] RDX: 0000000000000000 RSI: 000000000000000a RDI: ffff888005a7f080 > [ 20.940016][ T13] RBP: ffff888011dfc540 R08: 0000000000000000 R09: 0000000000000001 > [ 20.941227][ T13] R10: ffffffff82e508e0 R11: 0000000000000005 R12: ffff88800ddfbe58 > [ 20.942375][ T13] R13: ffff888005a7f080 R14: ffff888005a7f158 R15: ffff888005a7f158 > [ 20.943531][ T13] FS: 0000000000000000(0000) GS:ffff88803ea80000(0000) knlGS:0000000000000000 > [ 20.944838][ T13] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 20.945811][ T13] CR2: 0000000000000020 CR3: 0000000002e22006 CR4: 0000000000370ef0 > [ 20.946984][ T13] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 20.948150][ T13] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 20.949327][ T13] Call Trace: > [ 20.949949][ T13] <TASK> > [ 20.950374][ T13] ? __die_body.cold+0x19/0x26 > [ 20.951066][ T13] ? page_fault_oops+0x13e/0x2b0 > [ 20.951766][ T13] ? _printk+0x58/0x73 > [ 20.952358][ T13] ? do_user_addr_fault+0x5f/0x750 > [ 20.953120][ T13] ? exc_page_fault+0x76/0x240 > [ 20.953827][ T13] ? asm_exc_page_fault+0x22/0x30 > [ 20.954606][ T13] ? btrfs_bio_end_io+0xae/0xc0 [btrfs] > [ 20.955616][ T13] ? btrfs_log_dev_io_error+0x7f/0x90 [btrfs] > [ 20.956682][ T13] btrfs_orig_write_end_io+0x51/0x90 [btrfs] > [ 20.957769][ T13] dm_submit_bio+0x5c2/0xa50 [dm_mod] > [ 20.958623][ T13] ? find_held_lock+0x2b/0x80 > [ 20.959339][ T13] ? blk_try_enter_queue+0x90/0x1e0 > [ 20.960228][ T13] __submit_bio+0xe0/0x130 > [ 20.960879][ T13] ? ktime_get+0x10a/0x160 > [ 20.961546][ T13] ? lockdep_hardirqs_on+0x74/0x100 > [ 20.962310][ T13] submit_bio_noacct_nocheck+0x199/0x410 > [ 20.963140][ T13] btrfs_submit_bio+0x7d/0x150 [btrfs] > [ 20.964089][ T13] btrfs_submit_chunk+0x1a1/0x6d0 [btrfs] > [ 20.965066][ T13] ? lockdep_hardirqs_on+0x74/0x100 > [ 20.965824][ T13] ? __folio_start_writeback+0x10/0x2c0 > [ 20.966659][ T13] btrfs_submit_bbio+0x1c/0x40 [btrfs] > [ 20.967617][ T13] submit_one_bio+0x44/0x60 [btrfs] > [ 20.968536][ T13] submit_extent_folio+0x13f/0x330 [btrfs] > [ 20.969552][ T13] ? btrfs_set_range_writeback+0xa3/0xd0 [btrfs] > [ 20.970625][ T13] extent_writepage_io+0x18b/0x360 [btrfs] > [ 20.971632][ T13] extent_write_locked_range+0x17c/0x340 [btrfs] > [ 20.972702][ T13] ? __pfx_end_bbio_data_write+0x10/0x10 [btrfs] > [ 20.973857][ T13] run_delalloc_cow+0x71/0xd0 [btrfs] > [ 20.974841][ T13] btrfs_run_delalloc_range+0x176/0x500 [btrfs] > [ 20.975870][ T13] ? find_lock_delalloc_range+0x119/0x260 [btrfs] > [ 20.976911][ T13] writepage_delalloc+0x2ab/0x480 [btrfs] > [ 20.977792][ T13] extent_write_cache_pages+0x236/0x7d0 [btrfs] > [ 20.978728][ T13] btrfs_writepages+0x72/0x130 [btrfs] > [ 20.979531][ T13] do_writepages+0xd4/0x240 > [ 20.980111][ T13] ? find_held_lock+0x2b/0x80 > [ 20.980695][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 > [ 20.981461][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 > [ 20.982213][ T13] __writeback_single_inode+0x5c/0x4c0 > [ 20.982859][ T13] ? do_raw_spin_unlock+0x49/0xb0 > [ 20.983439][ T13] writeback_sb_inodes+0x22c/0x560 > [ 20.984079][ T13] __writeback_inodes_wb+0x4c/0xe0 > [ 20.984886][ T13] wb_writeback+0x1d6/0x3f0 > [ 20.985536][ T13] wb_workfn+0x334/0x520 > [ 20.986044][ T13] process_one_work+0x1ee/0x570 > [ 20.986580][ T13] ? lock_is_held_type+0xc6/0x130 > [ 20.987142][ T13] worker_thread+0x1d1/0x3b0 > [ 20.987918][ T13] ? __pfx_worker_thread+0x10/0x10 > [ 20.988690][ T13] kthread+0xee/0x120 > [ 20.989180][ T13] ? __pfx_kthread+0x10/0x10 > [ 20.989915][ T13] ret_from_fork+0x30/0x50 > [ 20.990615][ T13] ? __pfx_kthread+0x10/0x10 > [ 20.991336][ T13] ret_from_fork_asm+0x1a/0x30 > [ 20.992106][ T13] </TASK> > [ 20.992482][ T13] Modules linked in: dm_mod btrfs blake2b_generic xor raid6_pq rapl > [ 20.993406][ T13] CR2: 0000000000000020 > [ 20.993884][ T13] ---[ end trace 0000000000000000 ]--- > [ 20.993954][ T1415] BUG: kernel NULL pointer dereference, address: 0000000000000020 Can you trim the timestamps when applying? Otherwise looks good, Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c index 056f8a171bba..af12b23c8531 100644 --- a/fs/btrfs/bio.c +++ b/fs/btrfs/bio.c @@ -49,6 +49,7 @@ void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_fs_info *fs_info, bbio->end_io = end_io; bbio->private = private; atomic_set(&bbio->pending_ios, 1); + WRITE_ONCE(bbio->status, BLK_STS_OK); } /* @@ -120,41 +121,28 @@ static void __btrfs_bio_end_io(struct btrfs_bio *bbio) } } -static void btrfs_orig_write_end_io(struct bio *bio); - -static void btrfs_bbio_propagate_error(struct btrfs_bio *bbio, - struct btrfs_bio *orig_bbio) -{ - /* - * For writes we tolerate nr_mirrors - 1 write failures, so we can't - * just blindly propagate a write failure here. Instead increment the - * error count in the original I/O context so that it is guaranteed to - * be larger than the error tolerance. - */ - if (bbio->bio.bi_end_io == &btrfs_orig_write_end_io) { - struct btrfs_io_stripe *orig_stripe = orig_bbio->bio.bi_private; - struct btrfs_io_context *orig_bioc = orig_stripe->bioc; - - atomic_add(orig_bioc->max_errors, &orig_bioc->error); - } else { - orig_bbio->bio.bi_status = bbio->bio.bi_status; - } -} - void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status) { bbio->bio.bi_status = status; if (bbio->bio.bi_pool == &btrfs_clone_bioset) { struct btrfs_bio *orig_bbio = bbio->private; - if (bbio->bio.bi_status) - btrfs_bbio_propagate_error(bbio, orig_bbio); btrfs_cleanup_bio(bbio); bbio = orig_bbio; } - if (atomic_dec_and_test(&bbio->pending_ios)) + /* At this point, bbio always points to the original btrfs_bio. Save the + * first error in it. + */ + if (status != BLK_STS_OK) + cmpxchg(&bbio->status, BLK_STS_OK, status); + + if (atomic_dec_and_test(&bbio->pending_ios)) { + /* Load split bio's error which might be set above. */ + if (status == BLK_STS_OK) + bbio->bio.bi_status = READ_ONCE(bbio->status); __btrfs_bio_end_io(bbio); + } } static int next_repair_mirror(struct btrfs_failed_bio *fbio, int cur_mirror) diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h index e48612340745..566c3e1d077b 100644 --- a/fs/btrfs/bio.h +++ b/fs/btrfs/bio.h @@ -79,6 +79,9 @@ struct btrfs_bio { /* File system that this I/O operates on. */ struct btrfs_fs_info *fs_info; + /* Set the error status of split bio. */ + blk_status_t status; + /* * This member must come last, bio_alloc_bioset will allocate enough * bytes for entire btrfs_bio but relies on bio being last.
The purpose of btrfs_bbio_propagate_error() shall be propagating an error of split bio to its original btrfs_bio, and tell the error to the upper layer. However, it's not working well on some cases. * Case 1. Immediate (or quick) end_bio with an error When btrfs sends btrfs_bio to mirrored devices, btrfs calls btrfs_bio_end_io() when all the mirroring bios are completed. If that btrfs_bio was split, it is from btrfs_clone_bioset and its end_io function is btrfs_orig_write_end_io. For this case, btrfs_bbio_propagate_error() accesses the orig_bbio's bio context to increase the error count. That works well in most cases. However, if the end_io is called enough fast, orig_bbio's (remaining part after split) bio context may not be properly set at that time. Since the bio context is set when the orig_bbio (the last btrfs_bio) is sent to devices, that might be too late for earlier split btrfs_bio's completion. That will result in NULL pointer dereference. That bug is easily reproducible by running btrfs/146 on zoned devices [1] and it shows the following trace. [1] You need raid-stripe-tree feature as it create "-d raid0 -m raid1" FS. [ 20.923980][ T13] BUG: kernel NULL pointer dereference, address: 0000000000000020 [ 20.925234][ T13] #PF: supervisor read access in kernel mode [ 20.926122][ T13] #PF: error_code(0x0000) - not-present page [ 20.927118][ T13] PGD 0 P4D 0 [ 20.927607][ T13] Oops: Oops: 0000 [#1] PREEMPT SMP PTI [ 20.928424][ T13] CPU: 1 UID: 0 PID: 13 Comm: kworker/u32:1 Not tainted 6.11.0-rc7-BTRFS-ZNS+ #474 [ 20.929740][ T13] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 20.930697][ T13] Workqueue: writeback wb_workfn (flush-btrfs-5) [ 20.931643][ T13] RIP: 0010:btrfs_bio_end_io+0xae/0xc0 [btrfs] [ 20.932573][ T1415] BTRFS error (device dm-0): bdev /dev/mapper/error-test errs: wr 2, rd 0, flush 0, corrupt 0, gen 0 [ 20.932871][ T13] Code: ba e1 48 8b 7b 10 e8 f1 f5 f6 ff eb da 48 81 bf 10 01 00 00 40 0c 33 a0 74 09 40 88 b5 f1 00 00 00 eb b8 48 8b 85 18 01 00 00 <48> 8b 40 20 0f b7 50 24 f0 01 50 20 eb a3 0f 1f 40 00 90 90 90 90 [ 20.936623][ T13] RSP: 0018:ffffc9000006f248 EFLAGS: 00010246 [ 20.937543][ T13] RAX: 0000000000000000 RBX: ffff888005a7f080 RCX: ffffc9000006f1dc [ 20.938788][ T13] RDX: 0000000000000000 RSI: 000000000000000a RDI: ffff888005a7f080 [ 20.940016][ T13] RBP: ffff888011dfc540 R08: 0000000000000000 R09: 0000000000000001 [ 20.941227][ T13] R10: ffffffff82e508e0 R11: 0000000000000005 R12: ffff88800ddfbe58 [ 20.942375][ T13] R13: ffff888005a7f080 R14: ffff888005a7f158 R15: ffff888005a7f158 [ 20.943531][ T13] FS: 0000000000000000(0000) GS:ffff88803ea80000(0000) knlGS:0000000000000000 [ 20.944838][ T13] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 20.945811][ T13] CR2: 0000000000000020 CR3: 0000000002e22006 CR4: 0000000000370ef0 [ 20.946984][ T13] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 20.948150][ T13] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 20.949327][ T13] Call Trace: [ 20.949949][ T13] <TASK> [ 20.950374][ T13] ? __die_body.cold+0x19/0x26 [ 20.951066][ T13] ? page_fault_oops+0x13e/0x2b0 [ 20.951766][ T13] ? _printk+0x58/0x73 [ 20.952358][ T13] ? do_user_addr_fault+0x5f/0x750 [ 20.953120][ T13] ? exc_page_fault+0x76/0x240 [ 20.953827][ T13] ? asm_exc_page_fault+0x22/0x30 [ 20.954606][ T13] ? btrfs_bio_end_io+0xae/0xc0 [btrfs] [ 20.955616][ T13] ? btrfs_log_dev_io_error+0x7f/0x90 [btrfs] [ 20.956682][ T13] btrfs_orig_write_end_io+0x51/0x90 [btrfs] [ 20.957769][ T13] dm_submit_bio+0x5c2/0xa50 [dm_mod] [ 20.958623][ T13] ? find_held_lock+0x2b/0x80 [ 20.959339][ T13] ? blk_try_enter_queue+0x90/0x1e0 [ 20.960228][ T13] __submit_bio+0xe0/0x130 [ 20.960879][ T13] ? ktime_get+0x10a/0x160 [ 20.961546][ T13] ? lockdep_hardirqs_on+0x74/0x100 [ 20.962310][ T13] submit_bio_noacct_nocheck+0x199/0x410 [ 20.963140][ T13] btrfs_submit_bio+0x7d/0x150 [btrfs] [ 20.964089][ T13] btrfs_submit_chunk+0x1a1/0x6d0 [btrfs] [ 20.965066][ T13] ? lockdep_hardirqs_on+0x74/0x100 [ 20.965824][ T13] ? __folio_start_writeback+0x10/0x2c0 [ 20.966659][ T13] btrfs_submit_bbio+0x1c/0x40 [btrfs] [ 20.967617][ T13] submit_one_bio+0x44/0x60 [btrfs] [ 20.968536][ T13] submit_extent_folio+0x13f/0x330 [btrfs] [ 20.969552][ T13] ? btrfs_set_range_writeback+0xa3/0xd0 [btrfs] [ 20.970625][ T13] extent_writepage_io+0x18b/0x360 [btrfs] [ 20.971632][ T13] extent_write_locked_range+0x17c/0x340 [btrfs] [ 20.972702][ T13] ? __pfx_end_bbio_data_write+0x10/0x10 [btrfs] [ 20.973857][ T13] run_delalloc_cow+0x71/0xd0 [btrfs] [ 20.974841][ T13] btrfs_run_delalloc_range+0x176/0x500 [btrfs] [ 20.975870][ T13] ? find_lock_delalloc_range+0x119/0x260 [btrfs] [ 20.976911][ T13] writepage_delalloc+0x2ab/0x480 [btrfs] [ 20.977792][ T13] extent_write_cache_pages+0x236/0x7d0 [btrfs] [ 20.978728][ T13] btrfs_writepages+0x72/0x130 [btrfs] [ 20.979531][ T13] do_writepages+0xd4/0x240 [ 20.980111][ T13] ? find_held_lock+0x2b/0x80 [ 20.980695][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 [ 20.981461][ T13] ? wbc_attach_and_unlock_inode+0x12c/0x290 [ 20.982213][ T13] __writeback_single_inode+0x5c/0x4c0 [ 20.982859][ T13] ? do_raw_spin_unlock+0x49/0xb0 [ 20.983439][ T13] writeback_sb_inodes+0x22c/0x560 [ 20.984079][ T13] __writeback_inodes_wb+0x4c/0xe0 [ 20.984886][ T13] wb_writeback+0x1d6/0x3f0 [ 20.985536][ T13] wb_workfn+0x334/0x520 [ 20.986044][ T13] process_one_work+0x1ee/0x570 [ 20.986580][ T13] ? lock_is_held_type+0xc6/0x130 [ 20.987142][ T13] worker_thread+0x1d1/0x3b0 [ 20.987918][ T13] ? __pfx_worker_thread+0x10/0x10 [ 20.988690][ T13] kthread+0xee/0x120 [ 20.989180][ T13] ? __pfx_kthread+0x10/0x10 [ 20.989915][ T13] ret_from_fork+0x30/0x50 [ 20.990615][ T13] ? __pfx_kthread+0x10/0x10 [ 20.991336][ T13] ret_from_fork_asm+0x1a/0x30 [ 20.992106][ T13] </TASK> [ 20.992482][ T13] Modules linked in: dm_mod btrfs blake2b_generic xor raid6_pq rapl [ 20.993406][ T13] CR2: 0000000000000020 [ 20.993884][ T13] ---[ end trace 0000000000000000 ]--- [ 20.993954][ T1415] BUG: kernel NULL pointer dereference, address: 0000000000000020 * Case 2. Earlier completion of orig_bbio for mirrored btrfs_bios btrfs_bbio_propagate_error() assumes the end_io function for orig_bbio is called last among split bios. In that case, btrfs_orig_write_end_io() sets the bio->bi_status to BLK_STS_IOERR by seeing the bioc->error [2]. Otherwise, the increased orig_bio's bioc->error is not checked by anyone and return BLK_STS_OK to the upper layer. [2] Actually, this is not true. Because we only increases orig_bioc->errors by max_errors, the condition "atomic_read(&bioc->error) > bioc->max_errors" is still not met if only one split btrfs_bio fails. * Case 3. Later completion of orig_bbio for un-mirrored btrfs_bios In contrast to the above case, btrfs_bbio_propagate_error() is not working well if un-mirrored orig_bbio is completed last. It sets orig_bbio->bio.bi_status to the btrfs_bio's error. But, that is easily over-written by orig_bbio's completion status. If the status is BLK_STS_OK, the upper layer would not know the failure. * Solution Considering the above cases, we can only save the error status in the orig_bbio (remaining part after split) itself as it is always available. Also, the saved error status should be propagated when all the split btrfs_bios are finished (i.e, bbio->pending_ios == 0). This commit introduces "status" to btrfs_bbio and saves the first error of split bios to original btrfs_bio's "status" variable. When all the split bios are finished, the saved status is loaded into original btrfs_bio's status. With this commit, btrfs/146 on zoned devices does not hit the NULL pointer dereference. Fixes: 852eee62d31a ("btrfs: allow btrfs_submit_bio to split bios") CC: stable@vger.kernel.org # 6.6+ Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> --- - v1: https://lore.kernel.org/linux-btrfs/db5c272fc27c59ddded5c691373c26458698cb1a.1728489285.git.naohiro.aota@wdc.com/ - v2 - Replace atomic_t usage to blk_status_t and cmpxchg() --- fs/btrfs/bio.c | 36 ++++++++++++------------------------ fs/btrfs/bio.h | 3 +++ 2 files changed, 15 insertions(+), 24 deletions(-)