fsnotify: srcu to protect read side of inode and vfsmount locks

Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side.  This patch protects the read side of those lists
with a new single srcu.

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 5 insertions, 11 deletions

diff --git a/fs/notify/group.c b/fs/notify/group.c
index 7ac65ed4735b..48d3a6d6e47a 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -30,8 +30,6 @@
 
 /* protects writes to fsnotify_groups and fsnotify_mask */
 static DEFINE_MUTEX(fsnotify_grp_mutex);
-/* protects reads while running the fsnotify_groups list */
-struct srcu_struct fsnotify_grp_srcu;
 /* all groups registered to receive inode filesystem notifications */
 LIST_HEAD(fsnotify_inode_groups);
 /* all groups registered to receive mount point filesystem notifications */
@@ -50,18 +48,17 @@ void fsnotify_recalc_global_mask(void)
         struct fsnotify_group *group;
         __u32 inode_mask = 0;
         __u32 vfsmount_mask = 0;
-        int idx;
 
-        idx = srcu_read_lock(&fsnotify_grp_srcu);
+        mutex_lock(&fsnotify_grp_mutex);
         list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list)
                 inode_mask |= group->mask;
         list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list)
                 vfsmount_mask |= group->mask;
-                
-        srcu_read_unlock(&fsnotify_grp_srcu, idx);
 
         fsnotify_inode_mask = inode_mask;
         fsnotify_vfsmount_mask = vfsmount_mask;
+
+        mutex_unlock(&fsnotify_grp_mutex);
 }
 
 /*
@@ -168,6 +165,8 @@ static void fsnotify_destroy_group(struct fsnotify_group *group)
         /* clear all inode marks for this group */
         fsnotify_clear_marks_by_group(group);
 
+        synchronize_srcu(&fsnotify_mark_srcu);
+
         /* past the point of no return, matches the initial value of 1 */
         if (atomic_dec_and_test(&group->num_marks))
                 fsnotify_final_destroy_group(group);
@@ -216,12 +215,7 @@ void fsnotify_put_group(struct fsnotify_group *group)
          */
         __fsnotify_evict_group(group);
 
-        /*
-         * now it's off the list, so the only thing we might care about is
-         * srcu access....
-         */
         mutex_unlock(&fsnotify_grp_mutex);
-        synchronize_srcu(&fsnotify_grp_srcu);
 
         /* and now it is really dead. _Nothing_ could be seeing it */
         fsnotify_recalc_global_mask();