since FAN_ERROR doesn't apply to inode/mount marks, it should suffice to
only expose this information for superblock marks. Therefore, wrap this
kind of marks into a container and plumb it for the future.

Signed-off-by: Gabriel Krisman Bertazi <redacted>

---
Changes since v1:
  - Only extend superblock marks
---
 fs/notify/fanotify/fanotify.c      | 10 ++++++++--
 fs/notify/fanotify/fanotify.h      | 11 +++++++++++
 fs/notify/fanotify/fanotify_user.c | 29 ++++++++++++++++++++++++++++-
 include/linux/fsnotify_backend.h   |  1 +
 4 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 057abd2cf887..f85efb24cfb4 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c

@@ -867,9 +867,15 @@ static void fanotify_freeing_mark(struct fsnotify_mark *mark,
                dec_ucount(group->fanotify_data.ucounts, UCOUNT_FANOTIFY_MARKS);
 }

-static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
+static void fanotify_free_mark(struct fsnotify_mark *mark)
 {
-       kmem_cache_free(fanotify_mark_cache, fsn_mark);
+       if (mark->flags & FSNOTIFY_MARK_FLAG_SB) {
+               struct fanotify_sb_mark *fa_mark = FANOTIFY_SB_MARK(mark);
+
+               kmem_cache_free(fanotify_sb_mark_cache, fa_mark);
+       } else {
+               kmem_cache_free(fanotify_mark_cache, mark);
+       }
 }

 const struct fsnotify_ops fanotify_fsnotify_ops = {

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 4a5e555dc3d2..aec05e21d5a9 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h

@@ -6,6 +6,7 @@
 #include <linux/hashtable.h>

 extern struct kmem_cache *fanotify_mark_cache;
+extern struct kmem_cache *fanotify_sb_mark_cache;
 extern struct kmem_cache *fanotify_fid_event_cachep;
 extern struct kmem_cache *fanotify_path_event_cachep;
 extern struct kmem_cache *fanotify_perm_event_cachep;

@@ -129,6 +130,16 @@ static inline void fanotify_info_copy_name(struct fanotify_info *info,
               name->name);
 }

+struct fanotify_sb_mark {
+       struct fsnotify_mark fsn_mark;
+};
+
+static inline
+struct fanotify_sb_mark *FANOTIFY_SB_MARK(struct fsnotify_mark *mark)
+{
+       return container_of(mark, struct fanotify_sb_mark, fsn_mark);
+}
+
 /*
  * Common structure for fanotify events. Concrete structs are allocated in
  * fanotify_handle_event() and freed when the information is retrieved by

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index af518790a80f..db378480f1b1 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c

@@ -99,6 +99,7 @@ struct ctl_table fanotify_table[] = {
 extern const struct fsnotify_ops fanotify_fsnotify_ops;

 struct kmem_cache *fanotify_mark_cache __read_mostly;
+struct kmem_cache *fanotify_sb_mark_cache __read_mostly;
 struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
 struct kmem_cache *fanotify_path_event_cachep __read_mostly;
 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;

@@ -915,6 +916,27 @@ static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
        return mask & ~oldmask;
 }

+static struct fsnotify_mark *fanotify_alloc_mark(unsigned int type)
+{
+       struct fanotify_sb_mark *sb_mark;
+
+       switch (type) {
+       case FSNOTIFY_OBJ_TYPE_SB:
+               sb_mark = kmem_cache_zalloc(fanotify_sb_mark_cache, GFP_KERNEL);
+               if (!sb_mark)
+                       return NULL;
+               return &sb_mark->fsn_mark;
+
+       case FSNOTIFY_OBJ_TYPE_INODE:
+       case FSNOTIFY_OBJ_TYPE_PARENT:
+       case FSNOTIFY_OBJ_TYPE_VFSMOUNT:
+               return kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
+       default:
+               WARN_ON(1);
+               return NULL;
+       }
+}
+
 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
                                                   fsnotify_connp_t *connp,
                                                   unsigned int type,

@@ -933,13 +955,16 @@ static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
            !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
                return ERR_PTR(-ENOSPC);

-       mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
+       mark = fanotify_alloc_mark(type);
        if (!mark) {
                ret = -ENOMEM;
                goto out_dec_ucounts;
        }

        fsnotify_init_mark(mark, group);
+       if (type == FSNOTIFY_OBJ_TYPE_SB)
+               mark->flags |= FSNOTIFY_MARK_FLAG_SB;
+