[PATCH v3 6/7] fsnotify: send event "on child" to sb/mount marks

[Amir Goldstein <amir73il@gmail.com>]

Similar to events "on child" to watching directory, send event flavor
"on child" to sb/mount marks that specified interest in this flavor.
Event "on child" will not be sent on "orphan" children, that is, on
disconnected dentries and on a mount/sb root.

Currently, fanotify allows to set the FAN_EVENT_ON_CHILD flag on
sb/mount marks, but it was ignored.  Mask the flag explicitly until
fanotify implements support for events "on child" with name info
for sb/mount marks.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify_user.c |  7 ++++--
 fs/notify/fsnotify.c               | 38 ++++++++++++++++++++++++------
 include/linux/fsnotify_backend.h   | 23 ++++++++++++------
 3 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 030534da49e2..36c1327b32f4 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1146,10 +1146,13 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	}
 
 	/* inode held in place by reference to path; group by fget on fd */
-	if (mark_type == FAN_MARK_INODE)
+	if (mark_type == FAN_MARK_INODE) {
 		inode = path.dentry->d_inode;
-	else
+	} else {
 		mnt = path.mnt;
+		/* Mask out FAN_EVENT_ON_CHILD flag for sb/mount marks */
+		mask &= ~FAN_EVENT_ON_CHILD;
+	}
 
 	/* create/update an inode mark */
 	switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 72d332ce8e12..f6da8f263bc0 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -142,23 +142,50 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode)
 	spin_unlock(&inode->i_lock);
 }
 
-/* Notify this dentry's parent about a child's events. */
+/*
+ * Notify this dentry's parent about a child's events if parent is watching
+ * children or if sb/mount marks are interested in events with file_name info.
+ */
 int fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
 		    int data_type)
 {
+	const struct path *path = fsnotify_data_path(data, data_type);
+	struct mount *mnt = NULL;
+	bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;
+	__u32 test_mask = mask & FS_EVENTS_POSS_ON_CHILD;
+	__u32 p_mask, marks_mask = 0;
 	struct dentry *parent;
 	struct inode *p_inode;
 	int ret = 0;
 
-	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
+	if (path && path->mnt->mnt_root != dentry)
+		mnt = real_mount(path->mnt);
+
+	/*
+	 * FS_EVENT_ON_CHILD on sb/mount mask implies reporting events as if all
+	 * directories are watched.
+	 */
+	if (!IS_ROOT(dentry))
+		marks_mask |= fsnotify_watches_children(
+						dentry->d_sb->s_fsnotify_mask);
+	if (mnt)
+		marks_mask |= fsnotify_watches_children(
+						mnt->mnt_fsnotify_mask);
+
+
+	if (!(marks_mask & test_mask) && !parent_watched)
 		return 0;
 
 	parent = dget_parent(dentry);
 	p_inode = parent->d_inode;
+	p_mask = fsnotify_inode_watches_children(p_inode);
 
-	if (unlikely(!fsnotify_inode_watches_children(p_inode))) {
+	if (p_mask)
+		marks_mask |= p_mask;
+	else if (unlikely(parent_watched))
 		__fsnotify_update_child_dentry_flags(p_inode);
-	} else if (p_inode->i_fsnotify_mask & mask & ALL_FSNOTIFY_EVENTS) {
+
+	if (marks_mask & test_mask) {
 		struct name_snapshot name;
 
 		/* we are notifying a parent so come up with the new mask which
@@ -323,9 +350,6 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 		mnt = real_mount(path->mnt);
 		mnt_or_sb_mask |= mnt->mnt_fsnotify_mask;
 	}
-	/* An event "on child" is not intended for a mount/sb mark */
-	if (mask & FS_EVENT_ON_CHILD)
-		mnt_or_sb_mask = 0;
 
 	/*
 	 * Optimization: srcu_read_lock() has a memory barrier which can
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index f0c506405b54..ca461b95662a 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -50,8 +50,12 @@
 #define FS_DIR_MODIFY		0x00080000	/* Directory entry was modified */
 
 #define FS_EXCL_UNLINK		0x04000000	/* do not send events if object is unlinked */
-/* This inode cares about things that happen to its children.  Always set for
- * dnotify and inotify. */
+/*
+ * This inode cares about things that happen to its children.
+ * Always set for dnotify and inotify.
+ * Set on sb/mount marks mask to indicate interest in getting events with
+ * file_name information.
+ */
 #define FS_EVENT_ON_CHILD	0x08000000
 
 #define FS_DN_RENAME		0x10000000	/* file renamed */
@@ -386,14 +390,19 @@ extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 extern void fsnotify_sb_delete(struct super_block *sb);
 extern u32 fsnotify_get_cookie(void);
 
-static inline int fsnotify_inode_watches_children(struct inode *inode)
+static inline __u32 fsnotify_watches_children(__u32 mask)
 {
-	/* FS_EVENT_ON_CHILD is set if the inode may care */
-	if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
+	/* FS_EVENT_ON_CHILD is set if the object may care */
+	if (!(mask & FS_EVENT_ON_CHILD))
 		return 0;
-	/* this inode might care about child events, does it care about the
+	/* This object might care about child events, does it care about the
 	 * specific set of events that can happen on a child? */
-	return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
+	return mask & FS_EVENTS_POSS_ON_CHILD;
+}
+
+static inline int fsnotify_inode_watches_children(struct inode *inode)
+{
+	return fsnotify_watches_children(inode->i_fsnotify_mask);
 }
 
 /*
-- 
2.17.1