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@xxxxxxxxxxxxxx> Signed-off-by: Wang Shilong <wangsl.fnst@xxxxxxxxxxxxxx> --- fs/btrfs/scrub.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index 51c342b..f2f8803 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) -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
