Re: [PATCH 0/3 v2] xfs: Fix SEEK_HOLE implementation

[Jan Kara <jack@suse.cz>]

On Wed 17-05-17 16:57:46, Jan Kara wrote:
> On Wed 17-05-17 20:31:15, Eryu Guan wrote:
> > Hi Jan,
> > 
> > On Wed, May 17, 2017 at 02:10:43PM +0200, Jan Kara wrote:
> > > Hello,
> > > 
> > > this is the second revision of the patches to fix bugs in XFS's SEEK_HOLE
> > > implementation and cleanup the code a bit.
> > > 
> > > Changes since v1:
> > > * Fixed some more buggy cases
> > > * Simplified code a bit as suggested by Darrick
> > > * Fixed range check as spotted by Brian
> > 
> > I applied this patchset on top of 4.12-rc1 kernel to test your v4 test
> > case, your new test passed all my tests, but I found generic/285
> > regressed with sub-page block size XFS, 285.full showed that failure was
> > from subtest 7
> > 
> > 07. Test file with unwritten extents, only have dirty pages
> > 07.01 SEEK_HOLE expected 0 or 11264, got 0.                       succ
> > 07.02 SEEK_HOLE expected 1 or 11264, got 1.                       succ
> > 07.03 SEEK_DATA expected 10240 or 10240, got -1.                  FAIL
> > 07.04 SEEK_DATA expected 10240 or 10240, got -1.                  FAIL
> > 
> > And manual test showed subtest 8 failed too
> > 
> > # ./src/seek_sanity_test -s 8 -e 8 /mnt/xfs/testfile
> > File system magic#: 0x58465342
> > Allocation size: 4096
> > 
> > 08. Test file with unwritten extents, only have unwritten pages
> > 08.01 SEEK_HOLE expected 0 or 5632, got 0.                        succ
> > 08.02 SEEK_HOLE expected 1 or 5632, got 1.                        succ
> > 08.03 SEEK_DATA expected 5120 or 5120, got -1.                    FAIL
> > 08.04 SEEK_DATA expected 5120 or 5120, got -1.                    FAIL
> > 
> > Other subtests all passed with sub-page block size XFS.
> 
> Strange. It doesn't fail for me this way even with 1k blocksize. I'll
> investigate more tomorrow.

So I've been trying quite hard to reproduce the failure but I failed. Since
you are apparently getting some error out of lseek can you find out which
error it is (likely ENXIO but I'd like to confirm) and where it gets
generated? I don't see how it could possibly happen that SEEK_DATA would
miss that single page generated by this test and how any of my patches
would influence this particular situation. Thanks!

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR