| Message ID | 1460468176-534-1-git-send-email-anand.jain@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Tue, Apr 12, 2016 at 09:36:16PM +0800, Anand Jain wrote: > Move scratch super outside of the chunk lock to avoid below > lockdep warning. The better place to scratch super is in > the function btrfs_rm_dev_replace_free_srcdev() just before > free_device, which is outside of the chunk lock as well. > > To reproduce: > (fresh boot) > mkfs.btrfs -f -draid5 -mraid5 /dev/sdc /dev/sdd /dev/sde > mount /dev/sdc /btrfs > dd if=/dev/zero of=/btrfs/tf1 bs=4096 count=100 > (get devmgt from https://github.com/asj/devmgt.git) > devmgt detach /dev/sde > dd if=/dev/zero of=/btrfs/tf1 bs=4096 count=100 > sync > btrfs replace start -Brf 3 /dev/sdf /btrfs <-- > devmgt attach host7 > > ====================================================== > [ INFO: possible circular locking dependency detected ] > 4.6.0-rc2asj+ #1 Not tainted > --------------------------------------------------- > > btrfs/2174 is trying to acquire lock: > (sb_writers){.+.+.+}, at: > [<ffffffff812449b4>] __sb_start_write+0xb4/0xf0 > > but task is already holding lock: > (&fs_info->chunk_mutex){+.+.+.}, at: > [<ffffffffa05c5f55>] btrfs_dev_replace_finishing+0x145/0x980 [btrfs] > > which lock already depends on the new lock. > > Chain exists of: > sb_writers --> &fs_devs->device_list_mutex --> &fs_info->chunk_mutex > Possible unsafe locking scenario: > CPU0 CPU1 > ---- ---- > lock(&fs_info->chunk_mutex); > lock(&fs_devs->device_list_mutex); > lock(&fs_info->chunk_mutex); > lock(sb_writers); > > *** DEADLOCK *** > > -> #0 (sb_writers){.+.+.+}: > [<ffffffff810e6415>] __lock_acquire+0x1bc5/0x1ee0 > [<ffffffff810e707e>] lock_acquire+0xbe/0x210 > [<ffffffff810df49a>] percpu_down_read+0x4a/0xa0 > [<ffffffff812449b4>] __sb_start_write+0xb4/0xf0 > [<ffffffff81265534>] mnt_want_write+0x24/0x50 > [<ffffffff812508a2>] path_openat+0x952/0x1190 > [<ffffffff81252451>] do_filp_open+0x91/0x100 > [<ffffffff8123f5cc>] file_open_name+0xfc/0x140 > [<ffffffff8123f643>] filp_open+0x33/0x60 > [<ffffffffa0572bb6>] update_dev_time+0x16/0x40 [btrfs] > [<ffffffffa057f60d>] btrfs_scratch_superblocks+0x5d/0xb0 [btrfs] > [<ffffffffa057f70e>] btrfs_rm_dev_replace_remove_srcdev+0xae/0xd0 [btrfs] > [<ffffffffa05c62c5>] btrfs_dev_replace_finishing+0x4b5/0x980 [btrfs] > [<ffffffffa05c6ae8>] btrfs_dev_replace_start+0x358/0x530 [btrfs] > > Signed-off-by: Anand Jain <anand.jain@oracle.com> Added to for-next. -- 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
====================================================== [ INFO: possible circular locking dependency detected ] 4.6.0-rc2asj+ #1 Not tainted --------------------------------------------------- btrfs/2174 is trying to acquire lock: (sb_writers){.+.+.+}, at: [<ffffffff812449b4>] __sb_start_write+0xb4/0xf0 but task is already holding lock: (&fs_info->chunk_mutex){+.+.+.}, at: [<ffffffffa05c5f55>] btrfs_dev_replace_finishing+0x145/0x980 [btrfs] which lock already depends on the new lock. Chain exists of: sb_writers --> &fs_devs->device_list_mutex --> &fs_info->chunk_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->chunk_mutex); lock(&fs_devs->device_list_mutex); lock(&fs_info->chunk_mutex); lock(sb_writers); *** DEADLOCK *** -> #0 (sb_writers){.+.+.+}: [<ffffffff810e6415>] __lock_acquire+0x1bc5/0x1ee0 [<ffffffff810e707e>] lock_acquire+0xbe/0x210 [<ffffffff810df49a>] percpu_down_read+0x4a/0xa0 [<ffffffff812449b4>] __sb_start_write+0xb4/0xf0 [<ffffffff81265534>] mnt_want_write+0x24/0x50 [<ffffffff812508a2>] path_openat+0x952/0x1190 [<ffffffff81252451>] do_filp_open+0x91/0x100 [<ffffffff8123f5cc>] file_open_name+0xfc/0x140 [<ffffffff8123f643>] filp_open+0x33/0x60 [<ffffffffa0572bb6>] update_dev_time+0x16/0x40 [btrfs] [<ffffffffa057f60d>] btrfs_scratch_superblocks+0x5d/0xb0 [btrfs] [<ffffffffa057f70e>] btrfs_rm_dev_replace_remove_srcdev+0xae/0xd0 [btrfs] [<ffffffffa05c62c5>] btrfs_dev_replace_finishing+0x4b5/0x980 [btrfs] [<ffffffffa05c6ae8>] btrfs_dev_replace_start+0x358/0x530 [btrfs] Signed-off-by: Anand Jain <anand.jain@oracle.com> --- fs/btrfs/volumes.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 31bd791d6506..9d72dabdddfc 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1968,11 +1968,8 @@ void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_fs_info *fs_info, if (srcdev->missing) fs_devices->missing_devices--; - if (srcdev->writeable) { + if (srcdev->writeable) fs_devices->rw_devices--; - /* zero out the old super if it is writable */ - btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str); - } if (srcdev->bdev) fs_devices->open_devices--; @@ -1983,6 +1980,10 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info, { struct btrfs_fs_devices *fs_devices = srcdev->fs_devices; + if (srcdev->writeable) { + /* zero out the old super if it is writable */ + btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str); + } call_rcu(&srcdev->rcu, free_device); /*