| Message ID | 20160909230338.1493-1-anand.jain@oracle.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Sat, Sep 10, 2016 at 07:03:38AM +0800, Anand Jain wrote: > static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) > { > struct btrfs_device *device, *tmp; > + LIST_HEAD(pending_put); > + INIT_LIST_HEAD(&pending_put); LIST_HEAD declares and initializes the list to an empty one, not necessary to call INIT_LIST_HEAD. > > if (--fs_devices->opened > 0) > return 0; > @@ -906,9 +904,24 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) > mutex_lock(&fs_devices->device_list_mutex); > list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) { > btrfs_close_one_device(device); > + list_add(&device->dev_list, &pending_put); > } > mutex_unlock(&fs_devices->device_list_mutex); > > + /* > + * btrfs_show_devname() is using the device_list_mutex, > + * sometimes a call to blkdev_put() leads vfs calling > + * into this func. So do put outside of device_list_mutex, > + * as of now. > + */ > + while (!list_empty(&pending_put)) { > + device = list_entry(pending_put.next, Could be list_first_entry > + struct btrfs_device, dev_list); > + list_del(&device->dev_list); > + btrfs_close_bdev(device); > + call_rcu(&device->rcu, free_device); > + } > + > WARN_ON(fs_devices->open_devices); > WARN_ON(fs_devices->rw_devices); > fs_devices->opened = 0; After this patch, the function btrfs_close_one_device no longer does what it says, ie. it does not close the device. I'd have to look closer why it allocates a new structure and replaces it in the list, but this looks weird. -- 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
On 09/21/2016 10:26 PM, David Sterba wrote: > On Sat, Sep 10, 2016 at 07:03:38AM +0800, Anand Jain wrote: >> static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) >> { >> struct btrfs_device *device, *tmp; >> + LIST_HEAD(pending_put); >> + INIT_LIST_HEAD(&pending_put); > > LIST_HEAD declares and initializes the list to an empty one, not > necessary to call INIT_LIST_HEAD. Will use struct list_head makes it with inline with rest of the code. >> >> if (--fs_devices->opened > 0) >> return 0; >> @@ -906,9 +904,24 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) >> mutex_lock(&fs_devices->device_list_mutex); >> list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) { >> btrfs_close_one_device(device); >> + list_add(&device->dev_list, &pending_put); >> } >> mutex_unlock(&fs_devices->device_list_mutex); >> >> + /* >> + * btrfs_show_devname() is using the device_list_mutex, >> + * sometimes a call to blkdev_put() leads vfs calling >> + * into this func. So do put outside of device_list_mutex, >> + * as of now. >> + */ >> + while (!list_empty(&pending_put)) { >> + device = list_entry(pending_put.next, > > Could be list_first_entry ok. >> + struct btrfs_device, dev_list); >> + list_del(&device->dev_list); >> + btrfs_close_bdev(device); >> + call_rcu(&device->rcu, free_device); >> + } >> + >> WARN_ON(fs_devices->open_devices); >> WARN_ON(fs_devices->rw_devices); >> fs_devices->opened = 0; > > After this patch, the function btrfs_close_one_device no longer does > what it says, ie. it does not close the device. renamed to btrfs_prepare_close_one_device() > I'd have to look closer > why it allocates a new structure and replaces it in the list, but this > looks weird. I asked this in the ML quite sometime back. yeah reason is unknown. So this reason the sysfs patches (in the ML) is probably got x2 complicated. -Anand > -- > 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
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 1ce584893d1b..66dc3eeca6d0 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -877,8 +877,6 @@ static void btrfs_close_one_device(struct btrfs_device *device) if (device->missing) fs_devices->missing_devices--; - btrfs_close_bdev(device); - new_device = btrfs_alloc_device(NULL, &device->devid, device->uuid); BUG_ON(IS_ERR(new_device)); /* -ENOMEM */ @@ -892,13 +890,13 @@ static void btrfs_close_one_device(struct btrfs_device *device) list_replace_rcu(&device->dev_list, &new_device->dev_list); new_device->fs_devices = device->fs_devices; - - call_rcu(&device->rcu, free_device); } static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) { struct btrfs_device *device, *tmp; + LIST_HEAD(pending_put); + INIT_LIST_HEAD(&pending_put); if (--fs_devices->opened > 0) return 0; @@ -906,9 +904,24 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices) mutex_lock(&fs_devices->device_list_mutex); list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) { btrfs_close_one_device(device); + list_add(&device->dev_list, &pending_put); } mutex_unlock(&fs_devices->device_list_mutex); + /* + * btrfs_show_devname() is using the device_list_mutex, + * sometimes a call to blkdev_put() leads vfs calling + * into this func. So do put outside of device_list_mutex, + * as of now. + */ + while (!list_empty(&pending_put)) { + device = list_entry(pending_put.next, + struct btrfs_device, dev_list); + list_del(&device->dev_list); + btrfs_close_bdev(device); + call_rcu(&device->rcu, free_device); + } + WARN_ON(fs_devices->open_devices); WARN_ON(fs_devices->rw_devices); fs_devices->opened = 0;
btrfs_show_devname() is using the device_list_mutex, sometimes a call to blkdev_put() leads vfs calling into this func. So call blkdev_put() outside of device_list_mutex, as of now. [ 983.284212] ====================================================== [ 983.290401] [ INFO: possible circular locking dependency detected ] [ 983.296677] 4.8.0-rc5-ceph-00023-g1b39cec2 #1 Not tainted [ 983.302081] ------------------------------------------------------- [ 983.308357] umount/21720 is trying to acquire lock: [ 983.313243] (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff9128ec51>] blkdev_put+0x31/0x150 [ 983.321264] [ 983.321264] but task is already holding lock: [ 983.327101] (&fs_devs->device_list_mutex){+.+...}, at: [<ffffffffc033d6f6>] __btrfs_close_devices+0x46/0x200 [btrfs] [ 983.337839] [ 983.337839] which lock already depends on the new lock. [ 983.337839] [ 983.346024] [ 983.346024] the existing dependency chain (in reverse order) is: [ 983.353512] -> #4 (&fs_devs->device_list_mutex){+.+...}: [ 983.359096] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.365143] [<ffffffff91823125>] mutex_lock_nested+0x65/0x350 [ 983.371521] [<ffffffffc02d8116>] btrfs_show_devname+0x36/0x1f0 [btrfs] [ 983.378710] [<ffffffff9129523e>] show_vfsmnt+0x4e/0x150 [ 983.384593] [<ffffffff9126ffc7>] m_show+0x17/0x20 [ 983.389957] [<ffffffff91276405>] seq_read+0x2b5/0x3b0 [ 983.395669] [<ffffffff9124c808>] __vfs_read+0x28/0x100 [ 983.401464] [<ffffffff9124eb3b>] vfs_read+0xab/0x150 [ 983.407080] [<ffffffff9124ec32>] SyS_read+0x52/0xb0 [ 983.412609] [<ffffffff91825fc0>] entry_SYSCALL_64_fastpath+0x23/0xc1 [ 983.419617] -> #3 (namespace_sem){++++++}: [ 983.424024] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.430074] [<ffffffff918239e9>] down_write+0x49/0x80 [ 983.435785] [<ffffffff91272457>] lock_mount+0x67/0x1c0 [ 983.441582] [<ffffffff91272ab2>] do_add_mount+0x32/0xf0 [ 983.447458] [<ffffffff9127363a>] finish_automount+0x5a/0xc0 [ 983.453682] [<ffffffff91259513>] follow_managed+0x1b3/0x2a0 [ 983.459912] [<ffffffff9125b750>] lookup_fast+0x300/0x350 [ 983.465875] [<ffffffff9125d6e7>] path_openat+0x3a7/0xaa0 [ 983.471846] [<ffffffff9125ef75>] do_filp_open+0x85/0xe0 [ 983.477731] [<ffffffff9124c41c>] do_sys_open+0x14c/0x1f0 [ 983.483702] [<ffffffff9124c4de>] SyS_open+0x1e/0x20 [ 983.489240] [<ffffffff91825fc0>] entry_SYSCALL_64_fastpath+0x23/0xc1 [ 983.496254] -> #2 (&sb->s_type->i_mutex_key#3){+.+.+.}: [ 983.501798] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.507855] [<ffffffff918239e9>] down_write+0x49/0x80 [ 983.513558] [<ffffffff91366237>] start_creating+0x87/0x100 [ 983.519703] [<ffffffff91366647>] debugfs_create_dir+0x17/0x100 [ 983.526195] [<ffffffff911df153>] bdi_register+0x93/0x210 [ 983.532165] [<ffffffff911df313>] bdi_register_owner+0x43/0x70 [ 983.538570] [<ffffffff914080fb>] device_add_disk+0x1fb/0x450 [ 983.544888] [<ffffffff91580226>] loop_add+0x1e6/0x290 [ 983.550596] [<ffffffff91fec358>] loop_init+0x10b/0x14f [ 983.556394] [<ffffffff91002207>] do_one_initcall+0xa7/0x180 [ 983.562618] [<ffffffff91f932e0>] kernel_init_freeable+0x1cc/0x266 [ 983.569370] [<ffffffff918174be>] kernel_init+0xe/0x100 [ 983.575166] [<ffffffff9182620f>] ret_from_fork+0x1f/0x40 [ 983.581131] -> #1 (loop_index_mutex){+.+.+.}: [ 983.585801] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.591858] [<ffffffff91823125>] mutex_lock_nested+0x65/0x350 [ 983.598256] [<ffffffff9157ed3f>] lo_open+0x1f/0x60 [ 983.603704] [<ffffffff9128eec3>] __blkdev_get+0x123/0x400 [ 983.609757] [<ffffffff9128f4ea>] blkdev_get+0x34a/0x350 [ 983.615639] [<ffffffff9128f554>] blkdev_open+0x64/0x80 [ 983.621428] [<ffffffff9124aff6>] do_dentry_open+0x1c6/0x2d0 [ 983.627651] [<ffffffff9124c029>] vfs_open+0x69/0x80 [ 983.633181] [<ffffffff9125db74>] path_openat+0x834/0xaa0 [ 983.639152] [<ffffffff9125ef75>] do_filp_open+0x85/0xe0 [ 983.645035] [<ffffffff9124c41c>] do_sys_open+0x14c/0x1f0 [ 983.650999] [<ffffffff9124c4de>] SyS_open+0x1e/0x20 [ 983.656535] [<ffffffff91825fc0>] entry_SYSCALL_64_fastpath+0x23/0xc1 [ 983.663541] -> #0 (&bdev->bd_mutex){+.+.+.}: [ 983.668107] [<ffffffff910def43>] __lock_acquire+0x1003/0x17b0 [ 983.674510] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.680561] [<ffffffff91823125>] mutex_lock_nested+0x65/0x350 [ 983.686967] [<ffffffff9128ec51>] blkdev_put+0x31/0x150 [ 983.692761] [<ffffffffc033481f>] btrfs_close_bdev+0x4f/0x60 [btrfs] [ 983.699699] [<ffffffffc033d77b>] __btrfs_close_devices+0xcb/0x200 [btrfs] [ 983.707178] [<ffffffffc033d8db>] btrfs_close_devices+0x2b/0xa0 [btrfs] [ 983.714380] [<ffffffffc03081c5>] close_ctree+0x265/0x340 [btrfs] [ 983.721061] [<ffffffffc02d7959>] btrfs_put_super+0x19/0x20 [btrfs] [ 983.727908] [<ffffffff91250e2f>] generic_shutdown_super+0x6f/0x100 [ 983.734744] [<ffffffff91250f56>] kill_anon_super+0x16/0x30 [ 983.740888] [<ffffffffc02da97e>] btrfs_kill_super+0x1e/0x130 [btrfs] [ 983.747909] [<ffffffff91250fe9>] deactivate_locked_super+0x49/0x80 [ 983.754745] [<ffffffff912515fd>] deactivate_super+0x5d/0x70 [ 983.760977] [<ffffffff91270a1c>] cleanup_mnt+0x5c/0x80 [ 983.766773] [<ffffffff91270a92>] __cleanup_mnt+0x12/0x20 [ 983.772738] [<ffffffff910aa2fe>] task_work_run+0x7e/0xc0 [ 983.778708] [<ffffffff91081b5a>] exit_to_usermode_loop+0x7e/0xb4 [ 983.785373] [<ffffffff910039eb>] syscall_return_slowpath+0xbb/0xd0 [ 983.792212] [<ffffffff9182605c>] entry_SYSCALL_64_fastpath+0xbf/0xc1 [ 983.799225] [ 983.799225] other info that might help us debug this: [ 983.799225] [ 983.807291] Chain exists of: &bdev->bd_mutex --> namespace_sem --> &fs_devs->device_list_mutex [ 983.816521] Possible unsafe locking scenario: [ 983.816521] [ 983.822489] CPU0 CPU1 [ 983.827043] ---- ---- [ 983.831599] lock(&fs_devs->device_list_mutex); [ 983.836289] lock(namespace_sem); [ 983.842268] lock(&fs_devs->device_list_mutex); [ 983.849478] lock(&bdev->bd_mutex); [ 983.853127] [ 983.853127] *** DEADLOCK *** [ 983.853127] [ 983.859113] 3 locks held by umount/21720: [ 983.863145] #0: (&type->s_umount_key#35){++++..}, at: [<ffffffff912515f5>] deactivate_super+0x55/0x70 [ 983.872713] #1: (uuid_mutex){+.+.+.}, at: [<ffffffffc033d8d3>] btrfs_close_devices+0x23/0xa0 [btrfs] [ 983.882206] #2: (&fs_devs->device_list_mutex){+.+...}, at: [<ffffffffc033d6f6>] __btrfs_close_devices+0x46/0x200 [btrfs] [ 983.893422] [ 983.893422] stack backtrace: [ 983.897824] CPU: 6 PID: 21720 Comm: umount Not tainted 4.8.0-rc5-ceph-00023-g1b39cec2 #1 [ 983.905958] Hardware name: Supermicro SYS-5018R-WR/X10SRW-F, BIOS 1.0c 09/07/2015 [ 983.913492] 0000000000000000 ffff8c8a53c17a38 ffffffff91429521 ffffffff9260f4f0 [ 983.921018] ffffffff92642760 ffff8c8a53c17a88 ffffffff911b2b04 0000000000000050 [ 983.928542] ffffffff9237d620 ffff8c8a5294aee0 ffff8c8a5294aeb8 ffff8c8a5294aee0 [ 983.936072] Call Trace: [ 983.938545] [<ffffffff91429521>] dump_stack+0x85/0xc4 [ 983.943715] [<ffffffff911b2b04>] print_circular_bug+0x1fb/0x20c [ 983.949748] [<ffffffff910def43>] __lock_acquire+0x1003/0x17b0 [ 983.955613] [<ffffffff910dfd0c>] lock_acquire+0x1bc/0x1f0 [ 983.961123] [<ffffffff9128ec51>] ? blkdev_put+0x31/0x150 [ 983.966550] [<ffffffff91823125>] mutex_lock_nested+0x65/0x350 [ 983.972407] [<ffffffff9128ec51>] ? blkdev_put+0x31/0x150 [ 983.977832] [<ffffffff9128ec51>] blkdev_put+0x31/0x150 [ 983.983101] [<ffffffffc033481f>] btrfs_close_bdev+0x4f/0x60 [btrfs] [ 983.989500] [<ffffffffc033d77b>] __btrfs_close_devices+0xcb/0x200 [btrfs] [ 983.996415] [<ffffffffc033d8db>] btrfs_close_devices+0x2b/0xa0 [btrfs] [ 984.003068] [<ffffffffc03081c5>] close_ctree+0x265/0x340 [btrfs] [ 984.009189] [<ffffffff9126cc5e>] ? evict_inodes+0x15e/0x170 [ 984.014881] [<ffffffffc02d7959>] btrfs_put_super+0x19/0x20 [btrfs] [ 984.021176] [<ffffffff91250e2f>] generic_shutdown_super+0x6f/0x100 [ 984.027476] [<ffffffff91250f56>] kill_anon_super+0x16/0x30 [ 984.033082] [<ffffffffc02da97e>] btrfs_kill_super+0x1e/0x130 [btrfs] [ 984.039548] [<ffffffff91250fe9>] deactivate_locked_super+0x49/0x80 [ 984.045839] [<ffffffff912515fd>] deactivate_super+0x5d/0x70 [ 984.051525] [<ffffffff91270a1c>] cleanup_mnt+0x5c/0x80 [ 984.056774] [<ffffffff91270a92>] __cleanup_mnt+0x12/0x20 [ 984.062201] [<ffffffff910aa2fe>] task_work_run+0x7e/0xc0 [ 984.067625] [<ffffffff91081b5a>] exit_to_usermode_loop+0x7e/0xb4 [ 984.073747] [<ffffffff910039eb>] syscall_return_slowpath+0xbb/0xd0 [ 984.080038] [<ffffffff9182605c>] entry_SYSCALL_64_fastpath+0xbf/0xc1 Reported-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Anand Jain <anand.jain@oracle.com> --- v1->v2: Fix typo, remove static thanks Kdave. fs/btrfs/volumes.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)