diff options
| author | Anand Jain <anand.jain@oracle.com> | 2016-04-12 21:36:16 +0800 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2016-05-06 15:22:49 +0200 |
| commit | 48b3b9d401ec86899a52003b37331190a35a81a6 (patch) | |
| tree | 3593909dc3a941fdb7c9e567d64fba9b91e48be5 /fs/btrfs/volumes.c | |
| parent | 2473114981a36b4f0f57cf6e9548037d547a71b7 (diff) | |
btrfs: fix lock dep warning move scratch super outside of chunk_mutex
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>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/volumes.c')
| -rw-r--r-- | fs/btrfs/volumes.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 8d3ceb0fd239..c5e0d2d431dc 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1972,11 +1972,8 @@ 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--; @@ -1987,6 +1984,10 @@ 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); /* |