On Wed, Feb 18, 2026 at 12:31 AM Amir Goldstein <[email protected]> wrote:
>
> On Wed, Feb 18, 2026 at 5:22 AM T.J. Mercier <[email protected]> wrote:
> >
> > Add two new tests that verify inotify events are sent when memcg files
> > are removed.
> >
> > Signed-off-by: T.J. Mercier <[email protected]>
> > Acked-by: Tejun Heo <[email protected]>
>
> Feel free to add:
> Acked-by: Amir Goldstein <[email protected]>
Thanks!
> Although...
>
> > ---
> > .../selftests/cgroup/test_memcontrol.c | 122 ++++++++++++++++++
> > 1 file changed, 122 insertions(+)
> >
> > diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c
> > b/tools/testing/selftests/cgroup/test_memcontrol.c
> > index 4e1647568c5b..2b065d03b730 100644
> > --- a/tools/testing/selftests/cgroup/test_memcontrol.c
> > +++ b/tools/testing/selftests/cgroup/test_memcontrol.c
> > @@ -10,6 +10,7 @@
> > #include <sys/stat.h>
> > #include <sys/types.h>
> > #include <unistd.h>
> > +#include <sys/inotify.h>
> > #include <sys/socket.h>
> > #include <sys/wait.h>
> > #include <arpa/inet.h>
> > @@ -1625,6 +1626,125 @@ static int test_memcg_oom_group_score_events(const
> > char *root)
> > return ret;
> > }
> >
> > +static int read_event(int inotify_fd, int expected_event, int expected_wd)
> > +{
> > + struct inotify_event event;
> > + ssize_t len = 0;
> > +
> > + len = read(inotify_fd, &event, sizeof(event));
> > + if (len < (ssize_t)sizeof(event))
> > + return -1;
> > +
> > + if (event.mask != expected_event || event.wd != expected_wd) {
> > + fprintf(stderr,
> > + "event does not match expected values: mask %d
> > (expected %d) wd %d (expected %d)\n",
> > + event.mask, expected_event, event.wd, expected_wd);
> > + return -1;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int test_memcg_inotify_delete_file(const char *root)
> > +{
> > + int ret = KSFT_FAIL;
> > + char *memcg = NULL, *child_memcg = NULL;
> > + int fd, wd;
> > +
> > + memcg = cg_name(root, "memcg_test_0");
> > +
> > + if (!memcg)
> > + goto cleanup;
> > +
> > + if (cg_create(memcg))
> > + goto cleanup;
> > +
> > + if (cg_write(memcg, "cgroup.subtree_control", "+memory"))
> > + goto cleanup;
> > +
> > + child_memcg = cg_name(memcg, "child");
> > + if (!child_memcg)
> > + goto cleanup;
> > +
> > + if (cg_create(child_memcg))
> > + goto cleanup;
> > +
> > + fd = inotify_init1(0);
> > + if (fd == -1)
> > + goto cleanup;
> > +
> > + wd = inotify_add_watch(fd, cg_control(child_memcg,
> > "memory.events"), IN_DELETE_SELF);
> > + if (wd == -1)
> > + goto cleanup;
> > +
> > + cg_write(memcg, "cgroup.subtree_control", "-memory");
> > +
> > + if (read_event(fd, IN_DELETE_SELF, wd))
> > + goto cleanup;
> > +
> > + if (read_event(fd, IN_IGNORED, wd))
> > + goto cleanup;
> > +
> > + ret = KSFT_PASS;
> > +
> > +cleanup:
> > + if (fd >= 0)
> > + close(fd);
> > + if (child_memcg)
> > + cg_destroy(child_memcg);
> > + free(child_memcg);
> > + if (memcg)
> > + cg_destroy(memcg);
> > + free(memcg);
> > +
> > + return ret;
> > +}
> > +
> > +static int test_memcg_inotify_delete_rmdir(const char *root)
> > +{
> > + int ret = KSFT_FAIL;
> > + char *memcg = NULL;
> > + int fd, wd;
> > +
> > + memcg = cg_name(root, "memcg_test_0");
> > +
> > + if (!memcg)
> > + goto cleanup;
> > +
> > + if (cg_create(memcg))
> > + goto cleanup;
> > +
> > + fd = inotify_init1(0);
> > + if (fd == -1)
> > + goto cleanup;
> > +
> > + wd = inotify_add_watch(fd, cg_control(memcg, "memory.events"),
> > IN_DELETE_SELF);
> > + if (wd == -1)
> > + goto cleanup;
> > +
> > + if (cg_destroy(memcg))
> > + goto cleanup;
> > + free(memcg);
> > + memcg = NULL;
> > +
> > + if (read_event(fd, IN_DELETE_SELF, wd))
> > + goto cleanup;
> > +
> > + if (read_event(fd, IN_IGNORED, wd))
> > + goto cleanup;
> > +
> > + ret = KSFT_PASS;
> > +
> > +cleanup:
> > + if (fd >= 0)
> > + close(fd);
> > + if (memcg)
> > + cg_destroy(memcg);
> > + free(memcg);
> > +
> > + return ret;
> > +}
> > +
> > #define T(x) { x, #x }
> > struct memcg_test {
> > int (*fn)(const char *root);
> > @@ -1644,6 +1764,8 @@ struct memcg_test {
> > T(test_memcg_oom_group_leaf_events),
> > T(test_memcg_oom_group_parent_events),
> > T(test_memcg_oom_group_score_events),
> > + T(test_memcg_inotify_delete_file),
> > + T(test_memcg_inotify_delete_rmdir),
>
> How about another test case:
> - Watch the cgroup directory (not the child file)
> - Destroy cgroup
> - Expect IN_DELETE_SELF | IN_ISDIR
>
> I realize that this test won't pass with your implementation (right?)
> but that is not ok IMO.
Yes, that is correct, but I don't think any docs mention support for
monitoring kernfs directories, only files.
> If we wish to make IN_DELETE_SELF available for kernfs,
> it should not be confined to regular files IMO.
Based on what Honza discovered about i_nlink, it looks like we could
get VFS to send IN_DELETE_SELF for kernfs dirs with something like
this:
@@ -1540,6 +1558,9 @@ static void __kernfs_remove(struct kernfs_node *kn)
if (kernfs_type(pos) == KERNFS_FILE)
kernfs_notify_file_deleted(pos);
+ else if (kernfs_type(pos) == KERNFS_DIR)
+ kernfs_clear_inode_nlink(pos); <--
calls clear_nlink(inode); for every super
But I don't have a use for it at the moment.
