Re: [PATCH] Btrfs: fix missing delayed iputs on unmount

[Omar Sandoval <osandov@osandov.com>]

On Wed, Oct 31, 2018 at 03:41:47PM +0800, Lu Fengqi wrote:
> On Tue, Oct 30, 2018 at 05:14:42PM -0700, Omar Sandoval wrote:
> >From: Omar Sandoval <osandov@fb.com>
> >
> >There's a race between close_ctree() and cleaner_kthread().
> >close_ctree() sets btrfs_fs_closing(), and the cleaner stops when it
> >sees it set, but this is racy; the cleaner might have already checked
> >the bit and could be cleaning stuff. In particular, if it deletes unused
> >block groups, it will create delayed iputs for the free space cache
> >inodes. As of "btrfs: don't run delayed_iputs in commit", we're no
> >longer running delayed iputs after a commit. Therefore, if the cleaner
> >creates more delayed iputs after delayed iputs are run in
> >btrfs_commit_super(), we will leak inodes on unmount and get a busy
> 
> Since the assert added via commit e187831e1875 ("btrfs: assert on non-empty
> delayed iputs") wasn't triggered, it doesn't seem to be the cause of inode
> leak.

This was in our production build without CONFIG_BTRFS_ASSERT.