[LTP] [PATCH 5/5] syscalls/fanotify10: Add test cases for evictable ignore mark

[Amir Goldstein]

On Thu, Jun 30, 2022 at 9:27 AM Jan Stancek <jstancek@redhat.com> wrote:
>
> On Mon, Jun 13, 2022 at 4:39 PM Amir Goldstein <amir73il@gmail.com> wrote:
> >
> > Test multiple groups with evictable mark with ignore mask
> >
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > ---
> >  .../kernel/syscalls/fanotify/fanotify10.c     | 78 +++++++++++++++++++
> >  1 file changed, 78 insertions(+)
> >
> > diff --git a/testcases/kernel/syscalls/fanotify/fanotify10.c b/testcases/kernel/syscalls/fanotify/fanotify10.c
> > index b9a50672d..52277d0b7 100644
> > --- a/testcases/kernel/syscalls/fanotify/fanotify10.c
> > +++ b/testcases/kernel/syscalls/fanotify/fanotify10.c
> > @@ -71,6 +71,7 @@ static char event_buf[EVENT_BUF_LEN];
> >  static int exec_events_unsupported;
> >  static int fan_report_dfid_unsupported;
> >  static int filesystem_mark_unsupported;
> > +static int evictable_mark_unsupported;
> >
> >  #define MOUNT_PATH "fs_mnt"
> >  #define MNT2_PATH "mntpoint"
> > @@ -90,6 +91,10 @@ static int filesystem_mark_unsupported;
> >  #define FILE_EXEC_PATH2 MNT2_PATH"/"TEST_APP
> >  #define FILE2_EXEC_PATH2 MNT2_PATH"/"TEST_APP2
> >
> > +#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;
> > @@ -98,12 +103,14 @@ enum {
> >         FANOTIFY_INODE,
> >         FANOTIFY_MOUNT,
> >         FANOTIFY_FILESYSTEM,
> > +       FANOTIFY_EVICTABLE,
> >  };
> >
> >  static struct fanotify_mark_type fanotify_mark_types[] = {
> >         INIT_FANOTIFY_MARK_TYPE(INODE),
> >         INIT_FANOTIFY_MARK_TYPE(MOUNT),
> >         INIT_FANOTIFY_MARK_TYPE(FILESYSTEM),
> > +       INIT_FANOTIFY_MARK_TYPE(EVICTABLE),
> >  };
> >
> >  static struct tcase {
> > @@ -289,14 +296,59 @@ static struct tcase {
> >                 0,
> >                 FILE_PATH, FAN_OPEN, FAN_OPEN
> >         },
> > +       /* Evictable ignore mark test cases */
> > +       {
> > +               "don't ignore mount events created on file with evicted ignore mark",
> > +               MOUNT_PATH, FANOTIFY_MOUNT,
> > +               FILE_PATH, FANOTIFY_EVICTABLE,
> > +               0,
> > +               FILE_PATH, FAN_OPEN, FAN_OPEN
> > +       },
> > +       {
> > +               "don't ignore fs events created on a file with evicted ignore mark",
> > +               MOUNT_PATH, FANOTIFY_FILESYSTEM,
> > +               FILE_PATH, FANOTIFY_EVICTABLE,
> > +               0,
> > +               FILE_PATH, FAN_OPEN, FAN_OPEN
> > +       },
> > +       {
> > +               "don't ignore mount events created inside a parent with evicted ignore mark",
> > +               MOUNT_PATH, FANOTIFY_MOUNT,
> > +               DIR_PATH, FANOTIFY_EVICTABLE,
> > +               FAN_EVENT_ON_CHILD,
> > +               FILE_PATH, FAN_OPEN, FAN_OPEN
> > +       },
> > +       {
> > +               "don't ignore fs events created inside a parent with evicted ignore mark",
> > +               MOUNT_PATH, FANOTIFY_FILESYSTEM,
> > +               DIR_PATH, FANOTIFY_EVICTABLE,
> > +               FAN_EVENT_ON_CHILD,
> > +               FILE_PATH, FAN_OPEN, FAN_OPEN
> > +       },
>
> Hi,
>
> we are seeing some sporadic failures from this last testcase, with
> recent upstream kernels (v5.19-rc4-14-g941e3e791269).
> Has anyone also ran into it and knows if it's bug on test side or kernel?
>
> fanotify10.c:496: TINFO: Test #27: don't ignore fs events created
> inside a parent with evicted ignore mark
> fanotify10.c:338: TPASS: No fanotify inode marks as expected
> fanotify10.c:338: TPASS: No fanotify inode marks as expected
> fanotify10.c:338: TPASS: No fanotify inode marks as expected
> fanotify10.c:340: TFAIL: Unexpected inode mark (mflags=240,
> mask=8000020 ignored_mask=20)

It is a test bug.
The problem is that we want to evict an inode, but there is no
reliable mechanism to do that.

This is the reason for this workaround in fanotify23:

        /* Shrinkers on other fs do not work reliably enough to
guarantee mark eviction on drop_caches */
        .dev_fs_type = "ext2",

I did not encounter the problem with fanotify10 myself, but it should
be the same.
fanotify10 is not filesystem dependent, so if you can apply the same workaround
from fanotify23 and it works on your systems we can do that.

Thanks,
Amir.