fsnotify: parent event notification
inotify and dnotify both use a similar parent notification mechanism. We
add a generic parent notification mechanism to fsnotify for both of these
to use. This new machanism also adds the dentry flag optimization which
exists for inotify to dnotify.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index d565462..7fc7600 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -35,6 +35,97 @@
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
/*
+ * Given an inode, first check if we care what happens to our children. Inotify
+ * and dnotify both tell their parents about events. If we care about any event
+ * on a child we run all of our children and set a dentry flag saying that the
+ * parent cares. Thus when an event happens on a child it can quickly tell if
+ * if there is a need to find a parent and send the event to the parent.
+ */
+void __fsnotify_update_child_dentry_flags(struct inode *inode)
+{
+ struct dentry *alias;
+ int watched;
+
+ if (!S_ISDIR(inode->i_mode))
+ return;
+
+ /* determine if the children should tell inode about their events */
+ watched = fsnotify_inode_watches_children(inode);
+
+ spin_lock(&dcache_lock);
+ /* run all of the dentries associated with this inode. Since this is a
+ * directory, there damn well better only be one item on this list */
+ list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+ struct dentry *child;
+
+ /* run all of the children of the original inode and fix their
+ * d_flags to indicate parental interest (their parent is the
+ * original inode) */
+ list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
+ if (!child->d_inode)
+ continue;
+
+ spin_lock(&child->d_lock);
+ if (watched)
+ child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
+ else
+ child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
+ spin_unlock(&child->d_lock);
+ }
+ }
+ spin_unlock(&dcache_lock);
+}
+
+/* Notify this dentry's parent about a child's events. */
+void __fsnotify_parent(struct dentry *dentry, __u32 mask)
+{
+ struct dentry *parent;
+ struct inode *p_inode;
+ bool send = false;
+ bool should_update_children = false;
+
+ if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
+ return;
+
+ spin_lock(&dentry->d_lock);
+ parent = dentry->d_parent;
+ p_inode = parent->d_inode;
+
+ if (fsnotify_inode_watches_children(p_inode)) {
+ if (p_inode->i_fsnotify_mask & mask) {
+ dget(parent);
+ send = true;
+ }
+ } else {
+ /*
+ * The parent doesn't care about events on it's children but
+ * at least one child thought it did. We need to run all the
+ * children and update their d_flags to let them know p_inode
+ * doesn't care about them any more.
+ */
+ dget(parent);
+ should_update_children = true;
+ }
+
+ spin_unlock(&dentry->d_lock);
+
+ if (send) {
+ /* we are notifying a parent so come up with the new mask which
+ * specifies these are events which came from a child. */
+ mask |= FS_EVENT_ON_CHILD;
+
+ fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE);
+ dput(parent);
+ }
+
+ if (unlikely(should_update_children)) {
+ __fsnotify_update_child_dentry_flags(p_inode);
+ dput(parent);
+ }
+}
+EXPORT_SYMBOL_GPL(__fsnotify_parent);
+
+/*
* This is the main call to fsnotify. The VFS calls into hook specific functions
* in linux/fsnotify.h. Those functions then in turn call here. Here will call
* out to all of the registered fsnotify_group. Those groups can then use the