[LTP] [PATCH] fanotify10, fanotify23: fix cleanup of vfs_cache_pressure

[Wei Gao]

On Tue, Jun 24, 2025 at 07:41:46AM +0200, Amir Goldstein wrote:
> On Tue, Jun 24, 2025 at 6:39 AM Wei Gao <wegao@suse.com> wrote:
> >
> > On Mon, Jun 23, 2025 at 09:37:17AM +0200, Amir Goldstein wrote:
> > > Avoid setting vfs_cache_pressure to zero if test was not run
> > > because kernel does not support fanotify.
> > >
> > > Reported-by: Al Viro <viro@zeniv.linux.org.uk>
> > > Link: https://lore.kernel.org/linux-fsdevel/20250622215140.GX1880847@ZenIV/
> > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > ---
> > >  testcases/kernel/syscalls/fanotify/fanotify10.c | 8 ++++----
> > >  testcases/kernel/syscalls/fanotify/fanotify23.c | 8 ++++----
> > >  2 files changed, 8 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/testcases/kernel/syscalls/fanotify/fanotify10.c b/testcases/kernel/syscalls/fanotify/fanotify10.c
> > > index ccb4f55df..2d33416f3 100644
> > > --- a/testcases/kernel/syscalls/fanotify/fanotify10.c
> > > +++ b/testcases/kernel/syscalls/fanotify/fanotify10.c
> > > @@ -102,7 +102,6 @@ static int ignore_mark_unsupported;
> > >  #define DROP_CACHES_FILE "/proc/sys/vm/drop_caches"
> > >  #define CACHE_PRESSURE_FILE "/proc/sys/vm/vfs_cache_pressure"
> > >
> > > -static int old_cache_pressure;
> > >  static pid_t child_pid;
> > >  static int bind_mount_created;
> > >  static unsigned int num_classes = NUM_CLASSES;
> > > @@ -925,7 +924,6 @@ static void setup(void)
> > >       SAFE_MKDIR(MNT2_PATH, 0755);
> > >       mount_cycle();
> > >
> > > -     SAFE_FILE_SCANF(CACHE_PRESSURE_FILE, "%d", &old_cache_pressure);
> > >       /* Set high priority for evicting inodes */
> > >       SAFE_FILE_PRINTF(CACHE_PRESSURE_FILE, "500");
> > >  }
> > > @@ -939,8 +937,6 @@ static void cleanup(void)
> > >       if (bind_mount_created)
> > >               SAFE_UMOUNT(MNT2_PATH);
> > >
> > > -     SAFE_FILE_PRINTF(CACHE_PRESSURE_FILE, "%d", old_cache_pressure);
> > > -
> > >       for (i = 0; i < max_file_multi; i++) {
> > >               char path[PATH_MAX];
> > >
> > > @@ -972,6 +968,10 @@ static struct tst_test test = {
> > >               TEST_APP,
> > >               NULL
> > >       },
> > > +     .save_restore = (const struct tst_path_val[]) {
> > > +             {CACHE_PRESSURE_FILE, NULL, TST_SR_TCONF},
> > > +             {}
> > > +     },
> > >       .tags = (const struct tst_tag[]) {
> > >               {"linux-git", "9bdda4e9cf2d"},
> > >               {"linux-git", "2f02fd3fa13e"},
> > > diff --git a/testcases/kernel/syscalls/fanotify/fanotify23.c b/testcases/kernel/syscalls/fanotify/fanotify23.c
> > > index 26c9e87fb..36c7779da 100644
> > > --- a/testcases/kernel/syscalls/fanotify/fanotify23.c
> > > +++ b/testcases/kernel/syscalls/fanotify/fanotify23.c
> > > @@ -35,7 +35,6 @@
> > >  #define DROP_CACHES_FILE "/proc/sys/vm/drop_caches"
> > >  #define CACHE_PRESSURE_FILE "/proc/sys/vm/vfs_cache_pressure"
> > >
> > > -static int old_cache_pressure;
> > >  static int fd_notify;
> > >
> > >  static unsigned long long event_set[EVENT_MAX];
> > > @@ -234,7 +233,6 @@ static void setup(void)
> > >                                               FAN_MARK_FILESYSTEM,
> > >                                               FAN_ATTRIB, MOUNT_PATH);
> > >
> > > -     SAFE_FILE_SCANF(CACHE_PRESSURE_FILE, "%d", &old_cache_pressure);
> > >       /* Set high priority for evicting inodes */
> > >       SAFE_FILE_PRINTF(CACHE_PRESSURE_FILE, "500");
> > >  }
> > > @@ -243,8 +241,6 @@ static void cleanup(void)
> > >  {
> > >       if (fd_notify > 0)
> > >               SAFE_CLOSE(fd_notify);
> > > -
> > > -     SAFE_FILE_PRINTF(CACHE_PRESSURE_FILE, "%d", old_cache_pressure);
> > >  }
> > >
> > >  static struct tst_test test = {
> > > @@ -259,6 +255,10 @@ static struct tst_test test = {
> > >               {.type = "ext2"},
> > >               {}
> > >       },
> > > +     .save_restore = (const struct tst_path_val[]) {
> > > +             {CACHE_PRESSURE_FILE, NULL, TST_SR_TCONF},
> > > +             {}
> > > +     },
> > >  };
> > >
> > >  #else
> > > --
> > > 2.43.0
> >
> > For me this patch more looks like an improvement instead of a fix.
> > Thanks for your patch.
> >
> 
> It is a fix to the problem reported by Al Viro in the linked message.
Thanks, after check email carefully, i guess the the test skip initial
old_cache_pressure in setup but do wirte 0 to old_cache_pressure in
cleanup trigger the issue.
> 
> Thanks,
> Amir.