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authorAnand Jain <anand.jain@oracle.com>2016-04-12 16:36:16 +0300
committerDavid Sterba <dsterba@suse.com>2016-05-06 16:22:49 +0300
commit48b3b9d401ec86899a52003b37331190a35a81a6 (patch)
tree3593909dc3a941fdb7c9e567d64fba9b91e48be5 /fs/btrfs
parent2473114981a36b4f0f57cf6e9548037d547a71b7 (diff)
downloadlinux-48b3b9d401ec86899a52003b37331190a35a81a6.tar.xz
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')
-rw-r--r--fs/btrfs/volumes.c9
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);
/*