On Thu, May 18, 2017 at 11:03:46AM +0200, Jan Kara wrote:
> 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!
Yes, it's ENXIO, strace log:
...
open("/mnt/xfs/testfile07", O_RDWR|O_CREAT|O_TRUNC, 0644) = 3
write(1, "07. Test file with unwritten ext"..., 6007. Test file with unwritten extents, only have dirty pages
) = 60
fallocate(3, 0, 0, 11264) = 0
pwrite(3, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 1024, 10240) = 1024
lseek(3, 0, SEEK_HOLE) = 0
write(1, "07.01 SEEK_HOLE expected 0 or 11"..., 7107.01 SEEK_HOLE expected 0 or 11264, got 0. succ
) = 71
lseek(3, 1, SEEK_HOLE) = 1
write(1, "07.02 SEEK_HOLE expected 1 or 11"..., 7107.02 SEEK_HOLE expected 1 or 11264, got 1. succ
) = 71
lseek(3, 0, SEEK_DATA) = -1 ENXIO (No such device or address)
write(1, "07.03 SEEK_DATA expected 10240 o"..., 7107.03 SEEK_DATA expected 10240 or 10240, got -1. FAIL
) = 71
lseek(3, 1, SEEK_DATA) = -1 ENXIO (No such device or address)
write(1, "07.04 SEEK_DATA expected 10240 o"..., 7107.04 SEEK_DATA expected 10240 or 10240, got -1. FAIL
...
It's the second patch "xfs: Fix off-by-in in loop termination in
xfs_find_get_desired_pgoff()" introduced the issue for me. ENXIO was
returned from the if (nmap == 1) block in __xfs_seek_hole_data()
/*
* We only received one extent out of the two requested. This
* means we've hit EOF and didn't find what we are looking for.
*/
if (nmap == 1) {
....
/*
* If we were looking for data, it's nowhere to be found
*/
ASSERT(whence == SEEK_DATA);
error = -ENXIO;
goto out_error;
}
Seems that's because the do {} while() loop in xfs_find_get_desired_pgoff() was
broken out earlier due to patch 2.
/* Searching done if the page index is out of range. */
if (page->index >= end) {
goto out;
}
In my case, it returned earlier because page->index == end == 2.
I was testing with 1k block size xfs. xfs_info output:
meta-data=/dev/sdc2 isize=512 agcount=4, agsize=5242880 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1 spinodes=0 rmapbt=0
= reflink=0
data = bsize=1024 blocks=20971520, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=1024 blocks=10240, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Hope this helps, if you need more info please let me know.
Thanks,
Eryu
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