Re: [PATCH 06/10] xfs: move transaction handling to xfs_bmapi_convert_delalloc

[Christoph Hellwig <hch@lst.de>]

On Thu, Feb 14, 2019 at 11:38:16AM -0800, Darrick J. Wong wrote:
> > +	xfs_ilock(ip, XFS_ILOCK_EXCL);
> > +	xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
> 
> Aha, this is the problem -- this operation involves deferred rmap
> updates, which means that we have to retain the ILOCK until we've
> finished processing the rmap updates so that another thread cannot jump
> in and start modifying the file's bmap while we're still trying to
> finish the rmap updates.

Hmm, if our automatic unlock doesn't work with deferred operations
we should probably just get rid of that mechanism entirely, as it is
highly unsafe..

> 
> The patch below fixes generic/127 for me, for this configuration:
> 
> FSTYP=xfs
> MKFS_OPTIONS="-m reflink=1,rmapbt=1 -i sparse=1"
> MOUNT_OPTIONS="-o usrquota,grpquota,prjquota"

I didn't have -i sparc in my test config, but I doubt it makes
difference.  Let me check if I could reproduce the original issue
with it.