On Wed, Aug 30, 2017 at 12:53:21AM -0700, Christoph Hellwig wrote:
> On Tue, Aug 29, 2017 at 09:41:02PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Make sure that we update the rmapbt correctly when we collapse-range a
> > file and the extents on both sides of the hole can be merged. We can
> > construct this pretty trivially with insert-range and write, so test
> > that too.
>
> Does this break on the current tree? From code inspection I suspect
> the current code is doing the wrong thing there.
AFAICR the existing rmap code in bmse_shift_one /does/ work, though only
due to the subtlety that xfs_rmap_{,un}map_extent is smart enough to
automatically merge and unmerge rmap extents for you.
Hence if you have the following:
AAAAABBBAAAAAAAA
Where both A's could be merged after BBB goes away:
AAAAAAAAAAAAA---
The deferred rmap code will merge the two A regions into a single rmap
extent record automatically.
Hmm, so I guess that means that in the patch "xfs: use xfs_iext_*_extent
helpers in xfs_bmap_shift_extents" you can replace the three xfs_rmap
calls in xfs_bmse_merge with:
/* update reverse mapping */
error = xfs_rmap_unmap_extent(mp, dfops, ip, whichfork, got);
if (error)
return error;
memcpy(&new, got, sizeof(new));
new.br_startoff = left->br_startoff + left->br_blockcount;
return xfs_rmap_map_extent(mp, dfops, ip, whichfork, &new);
...which saves us a deferred op. Ok, will propose that in the actual
thread.
> > +./src/punch-alternating -o $((16 * blksz / file_blksz)) \
>
> Shouldn't we always use $here/src/progname ?
Ok, I didn't realize that. There are a lot of programs that still use ./src....
--D
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