Re: [PATCH 3/6] xfs: don't stall cowblocks scan if we can't take locks

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Jan 18, 2021 at 07:39:58PM +0000, Christoph Hellwig wrote:
> On Mon, Jan 18, 2021 at 11:37:18AM -0800, Darrick J. Wong wrote:
> > Ah, I see, you're asking why don't I make xfs_inode_walk responsible for
> > deciding what to do about EAGAIN, instead of open-coding that in the
> > ->execute function.  That would be a nice cleanup since the walk
> > function already has special casing for EFSCORRUPTED.
> > 
> > If I read you correctly, the relevant part of xfs_inode_walk becomes:
> > 
> > 	error = execute(batch[i]...);
> > 	xfs_irele(batch[i]);
> > 	if (error == -EAGAIN) {
> > 		if (args->flags & EOF_SYNC)
> > 			skipped++;
> > 		continue;
> > 	}
> > 
> > and the relevant part of xfs_inode_free_eofblocks becomes:
> > 
> > 	if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL))
> > 		return -EAGAIN;
> > 
> > I think that would work, and afaict it won't cause any serious problems
> > with the deferred inactivation series.
> 
> Exactly!

D'oh.  I tried making that change, but ran into the problem that *args
isn't necessarily an eofb structure, and xfs_qm_dqrele_all_inodes passes
a uint pointer.  I could define a new XFS_INODE_WALK_SYNC flag and
update the blockgc callers to set that if EOF_FLAGS_SYNC is set...

--D