On Fri, Apr 27, 2012 at 06:55:13PM +0800, Miao Xie wrote: > But I found you add a trylock for ->s_umount in cleaner_kthread(), this method > can fix the deadlock problem, I think. It may be introduced by the other patch, > could you send that patch to me? I found if we fail to trylock ->cleaner_mutex, > we will forget to unlock ->s_umount. the unlock was not visible within the diff context, the full patch is: --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1578,11 +1578,13 @@ static int cleaner_kthread(void *arg) vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE); if (!(root->fs_info->sb->s_flags & MS_RDONLY) && + down_read_trylock(&root->fs_info->sb->s_umount) && mutex_trylock(&root->fs_info->cleaner_mutex)) { btrfs_run_delayed_iputs(root); btrfs_clean_old_snapshots(root); mutex_unlock(&root->fs_info->cleaner_mutex); btrfs_run_defrag_inodes(root->fs_info); + up_read(&root->fs_info->sb->s_umount); } if (freezing(current)) { --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3413,7 +3413,9 @@ static int shrink_delalloc(struct btrfs_ max_reclaim >> PAGE_CACHE_SHIFT); while (loops < 1024) { /* have the flusher threads jump in and do some IO */ - smp_mb(); + if (btrfs_fs_closing(root->fs_info)) + return -EAGAIN; + nr_pages = min_t(unsigned long, nr_pages, root->fs_info->delalloc_bytes >> PAGE_CACHE_SHIFT); writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages); --- after close_tree starts the "fs_closing" check will prevent further calls to writeback. I don't remember from who the patch acutally comes from (via irc), it was noted as a workaround for the cleaner deadlock until it gets fully solved (re your patches http://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg13897.html and reference to balance and scrub: http://www.spinics.net/lists/linux-btrfs/msg14056.html ) david -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html