[PATCH v2 2/5] fsnotify: annotate filename events

[Amir Goldstein <amir73il@gmail.com>]

Filename events are referring to events that modify directory entries,
such as create,delete,rename. Those events should always be reported
on a watched directory, regardless if FS_EVENT_ON_CHILD is set
on the watch mask.

fsnotify_nameremove() and fsnotify_move() were modified to no longer
set the FS_EVENT_ON_CHILD event bit. This is a semantic change to
align with the filename event definition. It has no effect on any
existing backend, because dnotify and inotify always requets the
child events and fanotify does not get the delete,rename events.

The fsnotify_filename() helper is used to report all the filename
events. It gets a reference on parent dentry and passes it as the
data for the event along with the filename.

fsnotify_filename() is different from fsnotify_parent().
fsnotify_parent() is intended to report any events that happened on
child inodes when FS_EVENT_ON_CHILD is requested.
fsnotify_filename() is intended to report only filename events,
such as create,mkdir,link. Those events must always be reported
on a watched directory, regardless if FS_EVENT_ON_CHILD was requested.

fsnotify_d_name() is a helper for the common case where the
filename to pass is dentry->d_name.name.

It is safe to use these helpers with negative or not instantiated
dentries, such as the case with fsnotify_link() and
fsnotify_nameremove().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 include/linux/fsnotify.h | 40 +++++++++++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 9 deletions(-)

diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 9dadc0bcd7a9..d00ec5838d6e 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -17,8 +17,31 @@
 #include <linux/slab.h>
 #include <linux/bug.h>
 
+/*
+ * Notify this parent about a filename event (create,delete,rename).
+ * Unlike fsnotify_parent(), the event will be reported regardless of the
+ * FS_EVENT_ON_CHILD mask on the parent inode
+ */
+static inline int fsnotify_filename(struct dentry *parent, __u32 mask,
+				    const unsigned char *file_name, u32 cookie)
+{
+	return fsnotify(d_inode(parent), mask, parent, FSNOTIFY_EVENT_DENTRY,
+			file_name, cookie);
+}
+
+/*
+ * Call fsnotify_filename() with parent and d_name of this dentry.
+ * Safe to call with negative dentry, e.g. from fsnotify_nameremove()
+ */
+static inline int fsnotify_d_name(struct dentry *dentry, __u32 mask)
+{
+	return fsnotify_filename(dentry->d_parent, mask,
+				 dentry->d_name.name, 0);
+}
+
 /* Notify this dentry's parent about a child's events. */
-static inline int fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
+static inline int fsnotify_parent(const struct path *path,
+				  struct dentry *dentry, __u32 mask)
 {
 	if (!dentry)
 		dentry = path->dentry;
@@ -85,8 +108,8 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 {
 	struct inode *source = moved->d_inode;
 	u32 fs_cookie = fsnotify_get_cookie();
-	__u32 old_dir_mask = (FS_EVENT_ON_CHILD | FS_MOVED_FROM);
-	__u32 new_dir_mask = (FS_EVENT_ON_CHILD | FS_MOVED_TO);
+	__u32 old_dir_mask = FS_MOVED_FROM;
+	__u32 new_dir_mask = FS_MOVED_TO;
 	const unsigned char *new_name = moved->d_name.name;
 
 	if (old_dir == new_dir)
@@ -99,8 +122,7 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 
 	fsnotify(old_dir, old_dir_mask, source, FSNOTIFY_EVENT_INODE, old_name,
 		 fs_cookie);
-	fsnotify(new_dir, new_dir_mask, moved, FSNOTIFY_EVENT_DENTRY, new_name,
-		 fs_cookie);
+	fsnotify_filename(moved->d_parent, new_dir_mask, new_name, fs_cookie);
 
 	if (target)
 		fsnotify_link_count(target);
@@ -136,7 +158,7 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
 	if (isdir)
 		mask |= FS_ISDIR;
 
-	fsnotify_parent(NULL, dentry, mask);
+	fsnotify_d_name(dentry, mask);
 }
 
 /*
@@ -155,7 +177,7 @@ static inline void fsnotify_create(struct inode *inode, struct dentry *dentry)
 {
 	audit_inode_child(inode, dentry, AUDIT_TYPE_CHILD_CREATE);
 
-	fsnotify(inode, FS_CREATE, dentry, FSNOTIFY_EVENT_DENTRY, dentry->d_name.name, 0);
+	fsnotify_d_name(dentry, FS_CREATE);
 }
 
 /*
@@ -168,7 +190,7 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode, struct
 	fsnotify_link_count(inode);
 	audit_inode_child(dir, new_dentry, AUDIT_TYPE_CHILD_CREATE);
 
-	fsnotify(dir, FS_CREATE, new_dentry, FSNOTIFY_EVENT_DENTRY, new_dentry->d_name.name, 0);
+	fsnotify_d_name(new_dentry, FS_CREATE);
 }
 
 /*
@@ -180,7 +202,7 @@ static inline void fsnotify_mkdir(struct inode *inode, struct dentry *dentry)
 
 	audit_inode_child(inode, dentry, AUDIT_TYPE_CHILD_CREATE);
 
-	fsnotify(inode, mask, dentry, FSNOTIFY_EVENT_DENTRY, dentry->d_name.name, 0);
+	fsnotify_d_name(dentry, mask);
 }
 
 /*
-- 
2.17.1