[PATCH -v1 04/11] fsnotify: parent event notification

Eric Paris
2009-02-09T21:17:42Z

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>
---

fs/notify/inode_mark.c | 4 +
include/linux/dcache.h | 3 +
include/linux/fsnotify.h | 111 +++++++++++++++++++++++++++++++++++++-
include/linux/fsnotify_backend.h | 5 ++
4 files changed, 119 insertions(+), 4 deletions(-)

diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index 9a65fbc..840bd91 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -78,6 +78,8 @@ void fsnotify_recalc_inode_mask(struct inode *inode)
spin_lock(&inode->i_lock);
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
+
+ fsnotify_update_dentry_child_flags(inode);
}

void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
@@ -232,6 +234,8 @@ int fsnotify_add_mark(struct fsnotify_mark_entry *entry)
if (lentry) {
ret = -EEXIST;
fsnotify_put_mark(lentry);
+ } else {
+ fsnotify_update_dentry_child_flags(inode);
}

return ret;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c66d224..2b935f2 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -180,7 +180,8 @@ d_iput: no no no yes
#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
#define DCACHE_UNHASHED 0x0010

-#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
+#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
+#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0040 /* Parent inode is watched by some fsnotify listener */

#define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */

diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 6ae332f..736bb28 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -16,14 +16,102 @@
#include <linux/fsnotify_backend.h>
#include <linux/audit.h>

+static inline int fsnotify_inode_watches_children(struct inode *inode)
+{
+ if (inode->i_fsnotify_mask & (FS_EVENTS_WITH_CHILD << 32))
+ return 1;
+ return 0;
+}
+
+/*
+ * Get child dentry flag into synch with parent inode.
+ * Flag should always be clear for negative dentrys.A
+ *
+ * It's possible the flag could lie (false positive). fsnotify only
+ * automatically updates the flag when a new mark is added. The flag is NOT
+ * automatically updated when marks are removed because of the horrid tactics
+ * that would be needed to do this. When we remove marks from an inode we have
+ * no idea if that inode is sticking around aside from holding the i_lock. We
+ * clearly can't hold the i_lock across this function. It doesn't really
+ * matter though. The whole point is just to short cut the parent lookup for
+ * performance. False positives hurt perf, but they aren't a bad thing.
+ */
+static inline void fsnotify_update_dentry_child_flags(struct inode *inode)
+{
+ struct dentry *alias;
+ int watched = fsnotify_inode_watches_children(inode);
+
+ spin_lock(&dcache_lock);
+ list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+ struct dentry *child;
+
+ 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);
+}
+
/*
* fsnotify_d_instantiate - instantiate a dentry for inode
* Called with dcache_lock held.
*/
-static inline void fsnotify_d_instantiate(struct dentry *entry,
- struct inode *inode)
+static inline void fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
{
- inotify_d_instantiate(entry, inode);
+ struct dentry *parent;
+ struct inode *p_inode;
+
+ if (!inode)
+ return;
+
+ spin_lock(&dentry->d_lock);
+ parent = dentry->d_parent;
+ p_inode = parent->d_inode;
+
+ if (p_inode && fsnotify_inode_watches_children(p_inode))
+ dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
+ spin_unlock(&dentry->d_lock);
+
+ /* call the legacy inotify shit */
+ inotify_d_instantiate(dentry, inode);
+}
+
+/* Notify this dentry's parent about a child's events. */
+static inline void fsnotify_parent(struct dentry *dentry, __u64 orig_mask)
+{
+ struct dentry *parent;
+ struct inode *p_inode;
+ __u64 mask;
+
+ if (!(dentry->d_flags | DCACHE_FSNOTIFY_PARENT_WATCHED))
+ return;
+
+ /* we are notifying a parent so come up with the new mask which
+ * specifies these are events which came from a child. */
+ mask = (orig_mask & FS_EVENTS_WITH_CHILD) << 32;
+ /* need to remember if the child was a dir */
+ mask |= (orig_mask & FS_IN_ISDIR);
+
+ spin_lock(&dentry->d_lock);
+ parent = dentry->d_parent;
+ p_inode = parent->d_inode;
+
+ if (p_inode && (p_inode->i_fsnotify_mask & mask)) {
+ dget(parent);
+ spin_unlock(&dentry->d_lock);
+ fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE);
+ dput(parent);
+ } else {
+ spin_unlock(&dentry->d_lock);
+ }
}

/*
@@ -32,6 +120,14 @@ static inline void fsnotify_d_instantiate(struct dentry *entry,
*/
static inline void fsnotify_d_move(struct dentry *entry)
{
+ struct dentry *parent;
+
+ parent = entry->d_parent;
+ if (fsnotify_inode_watches_children(parent->d_inode))
+ entry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
+ else
+ entry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
+
inotify_d_move(entry);
}

@@ -96,6 +192,8 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
isdir = IN_ISDIR;
dnotify_parent(dentry, DN_DELETE);
inotify_dentry_parent_queue_event(dentry, IN_DELETE|isdir, 0, dentry->d_name.name);
+
+ fsnotify_parent(dentry, FS_DELETE|isdir);
}

/*
@@ -185,6 +283,7 @@ static inline void fsnotify_access(struct dentry *dentry)
inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

+ fsnotify_parent(dentry, mask);
fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
}

@@ -203,6 +302,7 @@ static inline void fsnotify_modify(struct dentry *dentry)
inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

+ fsnotify_parent(dentry, mask);
fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
}

@@ -220,6 +320,7 @@ static inline void fsnotify_open(struct dentry *dentry)
inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

+ fsnotify_parent(dentry, mask);
fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
}

@@ -240,6 +341,7 @@ static inline void fsnotify_close(struct file *file)
inotify_dentry_parent_queue_event(dentry, mask, 0, name);
inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

+ fsnotify_parent(dentry, mask);
fsnotify(inode, mask, file, FSNOTIFY_EVENT_FILE);
}

@@ -257,6 +359,7 @@ static inline void fsnotify_xattr(struct dentry *dentry)
inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

+ fsnotify_parent(dentry, mask);
fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
}

@@ -307,6 +410,8 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
inotify_inode_queue_event(inode, in_mask, 0, NULL, NULL);
inotify_dentry_parent_queue_event(dentry, in_mask, 0,
dentry->d_name.name);
+
+ fsnotify_parent(dentry, in_mask);
fsnotify(inode, in_mask, inode, FSNOTIFY_EVENT_INODE);
}
}
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index a9508c5..ad7294f 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -63,6 +63,11 @@
#define FS_DN_RENAME 0x1000000000000000ull /* file renamed */
#define FS_DN_MULTISHOT 0x2000000000000000ull /* dnotify multishot */

+#define FS_EVENTS_WITH_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
+ FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
+ FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
+ FS_DELETE)
+
/* when calling fsnotify tell it if the data is a path or inode */
#define FSNOTIFY_EVENT_PATH 1
#define FSNOTIFY_EVENT_INODE 2