fsnotify: allow ignored_mask to survive modification

Some inodes a group may want to never hear about a set of events even if
the inode is modified.  We add a new mark flag which indicates that these
marks should not have their ignored_mask cleared on modification.

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

2 files changed, 5 insertions, 2 deletions

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 3ad940d0bac1..54d58d5f72c1 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -148,7 +148,8 @@ void __fsnotify_flush_ignored_mask(struct inode *inode, void *data, int data_is)
         if (!hlist_empty(&inode->i_fsnotify_marks)) {
                 spin_lock(&inode->i_lock);
                 hlist_for_each_entry(mark, node, &inode->i_fsnotify_marks, i.i_list) {
-                        mark->ignored_mask = 0;
+                        if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
+                                mark->ignored_mask = 0;
                 }
                 spin_unlock(&inode->i_lock);
         }
@@ -160,7 +161,8 @@ void __fsnotify_flush_ignored_mask(struct inode *inode, void *data, int data_is)
                 if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
                         spin_lock(&mnt->mnt_root->d_lock);
                         hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
-                                mark->ignored_mask = 0;
+                                if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
+                                        mark->ignored_mask = 0;
                         }
                         spin_unlock(&mnt->mnt_root->d_lock);
                 }
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 018416ec5ce4..8ca19df8a171 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -271,6 +271,7 @@ struct fsnotify_mark {
 #define FSNOTIFY_MARK_FLAG_INODE                0x01
 #define FSNOTIFY_MARK_FLAG_VFSMOUNT             0x02
 #define FSNOTIFY_MARK_FLAG_OBJECT_PINNED        0x04
+#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x08
         unsigned int flags;             /* vfsmount or inode mark? */
         void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
 };