On Thu, Mar 25, 2021 at 05:21:18PM -0700, Darrick J. Wong wrote:

From: Christoph Hellwig <hch@lst.de>

Using xfs_inode_walk in xfs_qm_dqrele_all_inodes is complete overkill,
given that function simplify wants to iterate all live inodes known
to the VFS.  Just iterate over the s_inodes list.

I'm not sure that assertion is true. We attach dquots during inode
inactivation after the VFS has removed the inode from the s_inodes
list and evicted the inode. Hence there is a window between the
inode being removed from the sb->s_inodes lists and it being marked
XFS_IRECLAIMABLE where we can attach dquots to the inode.

Indeed, an inode marked XFS_IRECLAIMABLE that has gone through
evict -> destroy -> inactive -> nlink != 0 -> xfs_free_ eofblocks()
can have referenced dquots attached to it and require dqrele() to be
called to release them.

Hence I think that xfs_qm_dqrele_all_inodes() is broken if all it is
doing is walking vfs referenced inodes, because it doesn't actually
release the dquots attached to reclaimable inodes. If this did
actually release all dquots, then there wouldn't be a need for the
xfs_qm_dqdetach() call in xfs_reclaim_inode() just before it's
handed to RCU to be freed....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com