[LTP] [PATCH 1/1] nfs/nfs08.sh: Add test for NFS cache invalidation

[Petr Vorel]

> Hi!
> > v4 [1] of not yet upstreamed patch accidentally broke cache invalidation
> > for directories by clearing NFS_INO_INVALID_DATA inappropriately.
> > Although it was fixed in v5 [2] thus kernel was not actually broken,
> > it's better to prevent this in the future.

> > [1] https://lore.kernel.org/linux-nfs/167649314509.15170.15885497881041431304@noble.neil.brown.name/
> > [2] https://lore.kernel.org/linux-nfs/167943762461.8008.3152357340238024342@noble.neil.brown.name/

...
> > --- /dev/null
> > +++ b/testcases/network/nfs/nfs_stress/nfs08.sh
> > @@ -0,0 +1,20 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0-or-later
> > +# Copyright (c) 2023 Petr Vorel <pvorel@suse.cz>
> > +# Test reproducer for broken NFS cache invalidation for directories.
> > +# Based on reproducer from Neil Brown <neilb@suse.de>
> > +
> > +TST_TESTFUNC="do_test"
> > +
> > +do_test()
> > +{
> > +	tst_res TINFO "testing NFS cache invalidation for directories"
> > +
> > +	touch 1
> > +	EXPECT_PASS 'ls | grep 1'
> > +
> > +	touch 2
> > +	EXPECT_PASS 'ls | grep 2'
> > +}

> I do not get how this actually detects case invalidation, it probably
> does, but slightly better description how this actually excercises the
> case would help.

The behavior is:

"touch 1" asks for data invalidation (new file created), therefore following ls
(EXPECT_PASS 'ls | grep 1') fills the cache.  "touch 2" should again ask for
data invalidation, but it the unfixed v4 version of the patch it did not
resulted to cache invalidation.  Therefore second ls (EXPECT_PASS 'ls | grep 2')
shows just 1, but not 2. i.e. in the affected kernel only second ls failed,
but obviously both should be checked (nobody knows how another bug on cache
invalidation will behave).

I can add the description above to the commit message and adjust the comment in
the file.

Kind regards,
Petr

diff --git testcases/network/nfs/nfs_stress/nfs08.sh testcases/network/nfs/nfs_stress/nfs08.sh
index 8a0f40242..691e221d4 100755
--- testcases/network/nfs/nfs_stress/nfs08.sh
+++ testcases/network/nfs/nfs_stress/nfs08.sh
@@ -2,6 +2,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 # Copyright (c) 2023 Petr Vorel <pvorel@suse.cz>
 # Test reproducer for broken NFS cache invalidation for directories.
+# Kernel patch caused broken cache invalidation, which caused the second 'ls'
+# did not show '2'.
 # Based on reproducer from Neil Brown <neilb@suse.de>
 
 TST_TESTFUNC="do_test"