Re: [PATCH next 2/3] shmem: Fix data loss when folio truncated

[Hugh Dickins <hughd@google.com>]

On Fri, 7 Jan 2022, Matthew Wilcox wrote:
> On Sun, Jan 02, 2022 at 05:34:05PM -0800, Hugh Dickins wrote:
> > xfstests generic 098 214 263 286 412 used to pass on huge tmpfs (well,
> > three of those _require_odirect, enabled by a shmem_direct_IO() stub),
> > but still fail even with the partial_end fix.
> > 
> > generic/098 output mismatch shows actual data loss:
> >     --- tests/generic/098.out
> >     +++ /home/hughd/xfstests/results//generic/098.out.bad
> >     @@ -4,9 +4,7 @@
> >      wrote 32768/32768 bytes at offset 262144
> >      XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >      File content after remount:
> >     -0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa
> >     -*
> >     -0400000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >     +0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >     ...
> 
> generic/098 is passing for me ;-(  I'm using 'always' for THPs.
> I'll have to try harder.  Regardless, I think your fix is good ...

Worrying that the test behaves differently.  Your 'always':
you have '-o huge=always' in the exported TMPFS_MOUNT_OPTIONS?
That should be enough, but I admit to belt and braces by also
echo force > /sys/kernel/mm/transparent_hugepage/shmem_enabled

Hugh
I also back up with