Re: [PATCH] ovl: skip stale entries in merge dir cache iteration

[Miklos Szeredi <miklos@szeredi.hu>]

On Mon, 19 Jul 2021 at 18:43, Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Mon, Jul 19, 2021 at 6:24 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
> >
> > On Fri, 4 Jun 2021 at 12:43, Amir Goldstein <amir73il@gmail.com> wrote:
> > >
> > > On Mon, Apr 26, 2021 at 6:20 PM Amir Goldstein <amir73il@gmail.com> wrote:
> > > >
> > > > On the first getdents call, ovl_iterate() populates the readdir cache
> > > > with a list of entries, but for upper entries with origin lower inode,
> > > > p->ino remains zero.
> > > >
> > > > Following getdents calls traverse the readdir cache list and call
> > > > ovl_cache_update_ino() for entries with zero p->ino to lookup the entry
> > > > in the overlay and return d_ino that is consistent with st_ino.
> > > >
> > > > If the upper file was unlinked between the first getdents call and the
> > > > getdents call that lists the file entry, ovl_cache_update_ino() will not
> > > > find the entry and fall back to setting d_ino to the upper real st_ino,
> > > > which is inconsistent with how this object was presented to users.
> > > >
> > > > Instead of listing a stale entry with inconsistent d_ino, simply skip
> > > > the stale entry, which is better for users.
> > > >
> > >
> > > Miklos,
> > >
> > > I forgot to follow up on this patch.
> > > Upstream xfstest overlay/077 is failing without this patch.
> >
> > Can't reproduce (on ext4/xfs and "-oxino=on").
> >
> > Is there some trick?
>
> Not sure. overlay/077 fails for me on v5.14.0-rc2 on ext4/xfs.
>
>      QA output created by 077
>     +entry m100 has inconsistent d_ino (234 != 232)
>     +entry f100 has inconsistent d_ino (335 != 16777542)
>      Silence is golden
>
> Maybe you need to build src/t_dir_offset2?

root@kvm:/opt/xfstests-dev# git log -1 --pretty=%h
10f6b231
root@kvm:/opt/xfstests-dev# cat local.config
export TEST_DEV=/dev/vdb1
export TEST_DIR=/test
export SCRATCH_DEV=/dev/vdb2
export SCRATCH_MNT=/scratch
export FSTYP=ext4
export OVERLAY_MOUNT_OPTIONS="-o xino=on"
root@kvm:/opt/xfstests-dev# make src/t_dir_offset2
make: 'src/t_dir_offset2' is up to date.
root@kvm:/opt/xfstests-dev# ./check -overlay overlay/077
FSTYP         -- overlay
PLATFORM      -- Linux/x86_64 kvm 5.14.0-rc2 #276 SMP Tue Jul 20
05:54:44 CEST 2021
MKFS_OPTIONS  -- /scratch
MOUNT_OPTIONS -- -o xino=on /scratch /scratch/ovl-mnt

overlay/077 1s ...  1s
Ran: overlay/077
Passed all 1 tests

root@kvm:/opt/xfstests-dev# cat results/overlay/077.full

Create file in pure upper dir:
getdents at offset 0 returned 192 bytes
created entry p0
entry p0 found as expected

Remove file in pure upper dir:
getdents at offset 0 returned 192 bytes
unlinked entry p100
entry p100 not found as expected

Create file in impure upper dir:
getdents at offset 0 returned 192 bytes
created entry o0
entry o0 found as expected

Remove file in impure upper dir:
getdents at offset 0 returned 192 bytes
unlinked entry o100
entry o100 not found as expected

Create file in merge dir:
getdents at offset 0 returned 192 bytes
created entry m0
entry m0 found as expected

Remove file in merge dir:
getdents at offset 0 returned 192 bytes
unlinked entry m100
entry m100 not found as expected

Create file in former merge dir:
getdents at offset 0 returned 192 bytes
created entry f0
entry f0 found as expected

Remove file in former merge dir:
getdents at offset 0 returned 192 bytes
unlinked entry f100
entry f100 not found as expected

Ideas for further debugging why this test isn't failing for v4.12-rc2?

Thanks,
Miklos