Allow the FAN_FS_ERROR group mempool to grow up to an upper limit
dynamically, instead of starting already at the limit.  This doesn't
bother resizing on mark removal, but next time a mark is added, the slot
will be either reused or resized.  Also, if several marks are being
removed at once, most likely the group is going away anyway.

Signed-off-by: Gabriel Krisman Bertazi <redacted>
---
 fs/notify/fanotify/fanotify_user.c | 26 +++++++++++++++++++++-----
 include/linux/fsnotify_backend.h   |  1 +
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index f77581c5b97f..a860c286e885 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c

@@ -959,6 +959,10 @@ static int fanotify_remove_mark(struct fsnotify_group *group,

        removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
                                                 umask, &destroy_mark);
+
+       if (removed & FAN_FS_ERROR)
+               group->fanotify_data.error_event_marks--;
+
        if (removed & fsnotify_conn_mask(fsn_mark->connector))
                fsnotify_recalc_mask(fsn_mark->connector);
        if (destroy_mark)

@@ -1057,12 +1061,24 @@ static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,

 static int fanotify_group_init_error_pool(struct fsnotify_group *group)
 {
-       if (mempool_initialized(&group->fanotify_data.error_events_pool))
-               return 0;
+       int ret;
+
+       if (group->fanotify_data.error_event_marks >=
+           FANOTIFY_DEFAULT_MAX_FEE_POOL)
+               return -ENOMEM;

-       return mempool_init_kmalloc_pool(&group->fanotify_data.error_events_pool,
-                                        FANOTIFY_DEFAULT_MAX_FEE_POOL,
-                                        sizeof(struct fanotify_error_event));
+       if (!mempool_initialized(&group->fanotify_data.error_events_pool))
+               ret = mempool_init_kmalloc_pool(
+                               &group->fanotify_data.error_events_pool,
+                                1, sizeof(struct fanotify_error_event));
+       else
+               ret = mempool_resize(&group->fanotify_data.error_events_pool,
+                                    group->fanotify_data.error_event_marks + 1);
+
+       if (!ret)
+               group->fanotify_data.error_event_marks++;
+
+       return ret;
 }