diff options
| author | Wang Shilong <wangsl.fnst@cn.fujitsu.com> | 2014-02-19 19:24:17 +0800 |
|---|---|---|
| committer | Josef Bacik <jbacik@fb.com> | 2014-03-10 15:16:53 -0400 |
| commit | 12cf93728dfba237b46001a95479829c7179cdc9 (patch) | |
| tree | e109418ffb99606add276a2c4a7845881098b147 | |
| parent | 6cf7f77e6ba55cc1469aaf795507d274402892e9 (diff) | |
Btrfs: device_replace: fix deadlock for nocow case
commit cb7ab02156e4 cause a following deadlock found by
xfstests,btrfs/011:
Thread1 is commiting transaction which is blocked at
btrfs_scrub_pause().
Thread2 is calling btrfs_file_aio_write() which has held
inode's @i_mutex and commit transaction(blocked because
Thread1 is committing transaction).
Thread3 is copy_nocow_page worker which will also try to
hold inode @i_mutex, so thread3 will wait Thread1 finished.
Thread4 is waiting pending workers finished which will wait
Thread3 finished. So the problem is like this:
Thread1--->Thread4--->Thread3--->Thread2---->Thread1
Deadlock happens! we fix it by letting Thread1 go firstly,
which means we won't block transaction commit while we are
waiting pending workers finished.
Reported-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
| -rw-r--r-- | fs/btrfs/scrub.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index 51c342b9f5ef..f2f8803ea79c 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -2686,10 +2686,23 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx, wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0); - atomic_set(&sctx->wr_ctx.flush_all_writes, 0); + atomic_inc(&fs_info->scrubs_paused); + wake_up(&fs_info->scrub_pause_wait); + + /* + * must be called before we decrease @scrub_paused. + * make sure we don't block transaction commit while + * we are waiting pending workers finished. + */ wait_event(sctx->list_wait, atomic_read(&sctx->workers_pending) == 0); - scrub_blocked_if_needed(fs_info); + atomic_set(&sctx->wr_ctx.flush_all_writes, 0); + + mutex_lock(&fs_info->scrub_lock); + __scrub_blocked_if_needed(fs_info); + atomic_dec(&fs_info->scrubs_paused); + mutex_unlock(&fs_info->scrub_lock); + wake_up(&fs_info->scrub_pause_wait); btrfs_put_block_group(cache); if (ret) |