Message-ID: <20090327200515.32007.53032.stgit@paris.rdu.redhat.com>
Date:	Fri, 27 Mar 2009 16:05:15 -0400
From:	Eric Paris <eparis@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	viro@...iv.linux.org.uk, hch@...radead.org,
	alan@...rguk.ukuu.org.uk, sfr@...b.auug.org.au,
	john@...nmccutchan.com, rlove@...ve.org, akpm@...ux-foundation.org
Subject: [PATCH -V2 02/13] fsnotify: unified filesystem notification backend

fsnotify is a backend for filesystem notification.  fsnotify does
not provide any userspace interface but does provide the basis
needed for other notification schemes such as dnotify.  fsnotify
can be extended to be the backend for inotify or the upcoming
fanotify.  fsnotify provides a mechanism for "groups" to register for
some set of filesystem events and to then deliver those events to
those groups for processing.

fsnotify has a number of benefits, the first being actually shrinking the size
of an inode.  Before fsnotify to support both dnotify and inotify an inode had

        unsigned long           i_dnotify_mask; /* Directory notify events */
        struct dnotify_struct   *i_dnotify; /* for directory notifications */
        struct list_head        inotify_watches; /* watches on this inode */
        struct mutex            inotify_mutex;  /* protects the watches list

But with fsnotify this same functionallity (and more) is done with just

        __u32                   i_fsnotify_mask; /* all events for this inode */
        struct hlist_head       i_fsnotify_mark_entries; /* marks on this inode */

That's right, inotify, dnotify, and fanotify all in 64 bits.  We used that
much space just in inotify_watches alone, before this patch set.

fsnotify object lifetime and locking is MUCH better than what we have today.
inotify locking is incredibly complex.  See 8f7b0ba1c8539 as an example of
what's been busted since inception.  inotify needs to know internal semantics
of superblock destruction and unmounting to function.  The inode pinning and
vfs contortions are horrible.

no fsnotify implementers do allocation under locks.  This means things like
f04b30de3 which (due to an overabundance of caution) changes GFP_KERNEL to
GFP_NOFS can be reverted.  There are no longer any allocation rules when using
or implementing your own fsnotify listener.

fsnotify paves the way for fanotify.  people may not care for the original
companies that pushed for TALPA, but fanotify was designed with flexibility in
mind.  A first group that wants fanotify like interfaces is the readahead
group.  So they can be profiling at boot time in order to dynamicly tune
readahead to help with boot speed.  I've got other ideas how to use fanotify
to speed up boot when dealing with encrypted mounts, but I'm not ready to say
it yet since I don't know if my idea will work.

This patch series just builds fsnotify to the point that it can implement
dnotify and inotify_user.  Patches exist and will be sent soon after
acceptance to finish the in kernel inotify conversion (audit) and implement
fanotify.

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

 fs/notify/Kconfig                |   13 +++
 fs/notify/Makefile               |    2 
 fs/notify/fsnotify.c             |   79 ++++++++++++++++++
 fs/notify/fsnotify.h             |   17 ++++
 fs/notify/group.c                |  168 ++++++++++++++++++++++++++++++++++++++
 fs/notify/notification.c         |  116 ++++++++++++++++++++++++++
 include/linux/fsnotify.h         |  129 +++++++++++++++++++++--------
 include/linux/fsnotify_backend.h |  135 +++++++++++++++++++++++++++++++
 8 files changed, 622 insertions(+), 37 deletions(-)
 create mode 100644 fs/notify/fsnotify.c
 create mode 100644 fs/notify/fsnotify.h
 create mode 100644 fs/notify/group.c
 create mode 100644 fs/notify/notification.c
 create mode 100644 include/linux/fsnotify_backend.h

diff --git a/fs/notify/Kconfig b/fs/notify/Kconfig
index 50914d7..31dac7e 100644
--- a/fs/notify/Kconfig
+++ b/fs/notify/Kconfig
@@ -1,2 +1,15 @@
+config FSNOTIFY
+	bool "Filesystem notification backend"
+	default y
+	---help---
+	   fsnotify is a backend for filesystem notification.  fsnotify does
+	   not provide any userspace interface but does provide the basis
+	   needed for other notification schemes such as dnotify, inotify,
+	   and fanotify.
+
+	   Say Y here to enable fsnotify suport.
+
+	   If unsure, say Y.
+
 source "fs/notify/dnotify/Kconfig"
 source "fs/notify/inotify/Kconfig"
diff --git a/fs/notify/Makefile b/fs/notify/Makefile
index 5a95b60..db5467b 100644
--- a/fs/notify/Makefile
+++ b/fs/notify/Makefile
@@ -1,2 +1,4 @@
+obj-$(CONFIG_FSNOTIFY)		+= fsnotify.o notification.o group.o
+
 obj-y			+= dnotify/
 obj-y			+= inotify/
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
new file mode 100644
index 0000000..56bee0f
--- /dev/null
+++ b/fs/notify/fsnotify.c
@@ -0,0 +1,79 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@...hat.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/dcache.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/srcu.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+/*
+ * 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
+ * notification event in whatever means they feel necessary.
+ */
+void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
+{
+	struct fsnotify_group *group;
+	struct fsnotify_event *event = NULL;
+	int idx;
+
+	if (list_empty(&fsnotify_groups))
+		return;
+
+	if (!(mask & fsnotify_mask))
+		return;
+
+	/*
+	 * SRCU!!  the groups list is very very much read only and the path is
+	 * very hot.  The VAST majority of events are not going to need to do
+	 * anything other than walk the list so it's crazy to pre-allocate.
+	 */
+	idx = srcu_read_lock(&fsnotify_grp_srcu);
+	list_for_each_entry_rcu(group, &fsnotify_groups, group_list) {
+		if (mask & group->mask) {
+			if (!event) {
+				event = fsnotify_create_event(to_tell, mask, data, data_is);
+				/* shit, we OOM'd and now we can't tell, maybe
+				 * someday someone else will want to do something
+				 * here */
+				if (!event)
+					break;
+			}
+			group->ops->handle_event(group, event);
+		}
+	}
+	srcu_read_unlock(&fsnotify_grp_srcu, idx);
+	/*
+	 * fsnotify_create_event() took a reference so the event can't be cleaned
+	 * up while we are still trying to add it to lists, drop that one.
+	 */
+	if (event)
+		fsnotify_put_event(event);
+}
+EXPORT_SYMBOL_GPL(fsnotify);
+
+static __init int fsnotify_init(void)
+{
+	return init_srcu_struct(&fsnotify_grp_srcu);
+}
+subsys_initcall(fsnotify_init);
diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h
new file mode 100644
index 0000000..bf41e60
--- /dev/null
+++ b/fs/notify/fsnotify.h
@@ -0,0 +1,17 @@
+#ifndef _LINUX_FSNOTIFY_PRIVATE_H
+#define _LINUX_FSNOTIFY_PRIVATE_H
+
+#include <linux/dcache.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/spinlock.h>
+
+#include <linux/fsnotify.h>
+
+#include <asm/atomic.h>
+
+extern struct srcu_struct fsnotify_grp_srcu;
+extern struct list_head fsnotify_groups;
+extern __u32 fsnotify_mask;
+#endif	/* _LINUX_FSNOTIFY_PRIVATE_H */
diff --git a/fs/notify/group.c b/fs/notify/group.c
new file mode 100644
index 0000000..88d040b
--- /dev/null
+++ b/fs/notify/group.c
@@ -0,0 +1,168 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@...hat.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/srcu.h>
+#include <linux/rculist.h>
+#include <linux/wait.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+#include <asm/atomic.h>
+
+DEFINE_MUTEX(fsnotify_grp_mutex);
+struct srcu_struct fsnotify_grp_srcu;
+LIST_HEAD(fsnotify_groups);
+__u32 fsnotify_mask;
+
+void fsnotify_recalc_global_mask(void)
+{
+	struct fsnotify_group *group;
+	__u32 mask = 0;
+	int idx;
+
+	idx = srcu_read_lock(&fsnotify_grp_srcu);
+	list_for_each_entry_rcu(group, &fsnotify_groups, group_list) {
+		mask |= group->mask;
+	}
+	srcu_read_unlock(&fsnotify_grp_srcu, idx);
+	fsnotify_mask = mask;
+}
+
+static void fsnotify_add_group(struct fsnotify_group *group)
+{
+	list_add_rcu(&group->group_list, &fsnotify_groups);
+	group->evicted = 0;
+}
+
+static void fsnotify_get_group(struct fsnotify_group *group)
+{
+	atomic_inc(&group->refcnt);
+}
+
+static void fsnotify_destroy_group(struct fsnotify_group *group)
+{
+	if (group->ops->free_group_priv)
+		group->ops->free_group_priv(group);
+
+	kfree(group);
+}
+
+static void __fsnotify_evict_group(struct fsnotify_group *group)
+{
+	BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
+
+	if (!group->evicted)
+		list_del_rcu(&group->group_list);
+	group->evicted = 1;
+}
+
+void fsnotify_evict_group(struct fsnotify_group *group)
+{
+	mutex_lock(&fsnotify_grp_mutex);
+	__fsnotify_evict_group(group);
+	mutex_unlock(&fsnotify_grp_mutex);
+}
+
+void fsnotify_put_group(struct fsnotify_group *group)
+{
+	if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
+		return;
+
+	/* OK, now we know that there's no other users *and* we hold mutex,
+	 * so no new references will appear */
+	__fsnotify_evict_group(group);
+
+	/* now it's off the list, so the only thing we might care about is
+	 * srcu acces.... */
+	mutex_unlock(&fsnotify_grp_mutex);
+	synchronize_srcu(&fsnotify_grp_srcu);
+
+	/* and now it is really dead. _Nothing_ could be seeing it */
+	fsnotify_recalc_global_mask();
+	fsnotify_destroy_group(group);
+}
+
+static struct fsnotify_group *fsnotify_find_group(unsigned int group_num, __u32 mask,
+						  const struct fsnotify_ops *ops)
+{
+	struct fsnotify_group *group_iter;
+	struct fsnotify_group *group = NULL;
+
+	BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
+
+	list_for_each_entry_rcu(group_iter, &fsnotify_groups, group_list) {
+		if (group_iter->group_num == group_num) {
+			if ((group_iter->mask == mask) &&
+			    (group_iter->ops == ops)) {
+				fsnotify_get_group(group_iter);
+				group = group_iter;
+			} else
+				group = ERR_PTR(-EEXIST);
+		}
+	}
+	return group;
+}
+
+/*
+ * Either finds an existing group which matches the group_num, mask, and ops or
+ * creates a new group and adds it to the global group list.  In either case we
+ * take a reference for the group returned.
+ *
+ * low use function, could be faster to check if the group is there before we do
+ * the allocation and the initialization, but this is only called when notification
+ * systems make changes, so why make it more complex?
+ */
+struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
+					     const struct fsnotify_ops *ops)
+{
+	struct fsnotify_group *group, *tgroup;
+
+	group = kmalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
+	if (!group)
+		return ERR_PTR(-ENOMEM);
+
+	atomic_set(&group->refcnt, 1);
+
+	group->group_num = group_num;
+	group->mask = mask;
+
+	group->ops = ops;
+
+	mutex_lock(&fsnotify_grp_mutex);
+	tgroup = fsnotify_find_group(group_num, mask, ops);
+	if (tgroup) {
+		/* group already exists */
+		mutex_unlock(&fsnotify_grp_mutex);
+		/* destroy the new one we made */
+		fsnotify_put_group(group);
+		return tgroup;
+	}
+
+	/* group not found, add a new one */
+	fsnotify_add_group(group);
+	mutex_unlock(&fsnotify_grp_mutex);
+
+	if (mask)
+		fsnotify_recalc_global_mask();
+
+	return group;
+}
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
new file mode 100644
index 0000000..eb23a69
--- /dev/null
+++ b/fs/notify/notification.c
@@ -0,0 +1,116 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@...hat.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/mount.h>
+#include <linux/mutex.h>
+#include <linux/namei.h>
+#include <linux/path.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <asm/atomic.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+static struct kmem_cache *event_kmem_cache;
+
+void fsnotify_get_event(struct fsnotify_event *event)
+{
+	atomic_inc(&event->refcnt);
+}
+
+void fsnotify_put_event(struct fsnotify_event *event)
+{
+	if (!event)
+		return;
+
+	if (atomic_dec_and_test(&event->refcnt)) {
+		if (event->data_type == FSNOTIFY_EVENT_PATH) {
+			path_put(&event->path);
+			event->path.dentry = NULL;
+			event->path.mnt = NULL;
+		}
+
+		event->mask = 0;
+
+		kmem_cache_free(event_kmem_cache, event);
+	}
+}
+
+struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, int data_type)
+{
+	struct fsnotify_event *event;
+
+	event = kmem_cache_alloc(event_kmem_cache, GFP_KERNEL);
+	if (!event)
+		return NULL;
+
+	atomic_set(&event->refcnt, 1);
+
+	spin_lock_init(&event->lock);
+
+	event->path.dentry = NULL;
+	event->path.mnt = NULL;
+	event->inode = NULL;
+
+	event->to_tell = to_tell;
+
+	switch (data_type) {
+	case FSNOTIFY_EVENT_FILE: {
+		struct file *file = data;
+		struct path *path = &file->f_path;
+		event->path.dentry = path->dentry;
+		event->path.mnt = path->mnt;
+		path_get(&event->path);
+		event->data_type = FSNOTIFY_EVENT_PATH;
+		break;
+	}
+	case FSNOTIFY_EVENT_PATH: {
+		struct path *path = data;
+		event->path.dentry = path->dentry;
+		event->path.mnt = path->mnt;
+		path_get(&event->path);
+		event->data_type = FSNOTIFY_EVENT_PATH;
+		break;
+	}
+	case FSNOTIFY_EVENT_INODE:
+		event->inode = data;
+		event->data_type = FSNOTIFY_EVENT_INODE;
+		break;
+	default:
+		BUG();
+	};
+
+	event->mask = mask;
+
+	return event;
+}
+
+__init int fsnotify_notification_init(void)
+{
+	event_kmem_cache = kmem_cache_create("fsnotify_event", sizeof(struct fsnotify_event), 0, SLAB_PANIC, NULL);
+
+	return 0;
+}
+subsys_initcall(fsnotify_notification_init);
+
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 00fbd5b..3d68058 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -13,6 +13,7 @@
 
 #include <linux/dnotify.h>
 #include <linux/inotify.h>
+#include <linux/fsnotify_backend.h>
 #include <linux/audit.h>
 
 /*
@@ -35,6 +36,17 @@ static inline void fsnotify_d_move(struct dentry *entry)
 }
 
 /*
+ * fsnotify_inoderemove - an inode is going away
+ */
+static inline void fsnotify_inoderemove(struct inode *inode)
+{
+	inotify_inode_queue_event(inode, IN_DELETE_SELF, 0, NULL, NULL);
+	inotify_inode_is_dead(inode);
+
+	fsnotify(inode, FS_DELETE_SELF, inode, FSNOTIFY_EVENT_INODE);
+}
+
+/*
  * fsnotify_move - file old_name at old_dir was moved to new_name at new_dir
  */
 static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
@@ -43,28 +55,42 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 {
 	struct inode *source = moved->d_inode;
 	u32 cookie = inotify_get_cookie();
+	__u32 old_dir_mask = 0;
+	__u32 new_dir_mask = 0;
 
-	if (old_dir == new_dir)
+	if (old_dir == new_dir) {
 		inode_dir_notify(old_dir, DN_RENAME);
-	else {
+		old_dir_mask = FS_DN_RENAME;
+	} else {
 		inode_dir_notify(old_dir, DN_DELETE);
+		old_dir_mask = FS_DELETE;
 		inode_dir_notify(new_dir, DN_CREATE);
+		new_dir_mask = FS_CREATE;
 	}
 
-	if (isdir)
+	if (isdir) {
 		isdir = IN_ISDIR;
+		old_dir_mask |= FS_IN_ISDIR;
+		new_dir_mask |= FS_IN_ISDIR;
+	}
+
+	old_dir_mask |= FS_MOVED_FROM;
+	new_dir_mask |= FS_MOVED_TO;
+
 	inotify_inode_queue_event(old_dir, IN_MOVED_FROM|isdir,cookie,old_name,
 				  source);
 	inotify_inode_queue_event(new_dir, IN_MOVED_TO|isdir, cookie, new_name,
 				  source);
 
-	if (target) {
-		inotify_inode_queue_event(target, IN_DELETE_SELF, 0, NULL, NULL);
-		inotify_inode_is_dead(target);
-	}
+	fsnotify(old_dir, old_dir_mask, old_dir, FSNOTIFY_EVENT_INODE);
+	fsnotify(new_dir, new_dir_mask, new_dir, FSNOTIFY_EVENT_INODE);
+
+	if (target)
+		fsnotify_inoderemove(target);
 
 	if (source) {
 		inotify_inode_queue_event(source, IN_MOVE_SELF, 0, NULL, NULL);
+		fsnotify(source, FS_MOVE_SELF, moved->d_inode, FSNOTIFY_EVENT_INODE);
 	}
 	audit_inode_child(new_name, moved, new_dir);
 }
@@ -75,26 +101,19 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
 {
 	if (isdir)
-		isdir = IN_ISDIR;
+		isdir = FS_IN_ISDIR;
 	dnotify_parent(dentry, DN_DELETE);
 	inotify_dentry_parent_queue_event(dentry, IN_DELETE|isdir, 0, dentry->d_name.name);
 }
 
 /*
- * fsnotify_inoderemove - an inode is going away
- */
-static inline void fsnotify_inoderemove(struct inode *inode)
-{
-	inotify_inode_queue_event(inode, IN_DELETE_SELF, 0, NULL, NULL);
-	inotify_inode_is_dead(inode);
-}
-
-/*
  * fsnotify_link_count - inode's link count changed
  */
 static inline void fsnotify_link_count(struct inode *inode)
 {
 	inotify_inode_queue_event(inode, IN_ATTRIB, 0, NULL, NULL);
+
+	fsnotify(inode, FS_ATTRIB, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -106,6 +125,8 @@ static inline void fsnotify_create(struct inode *inode, struct dentry *dentry)
 	inotify_inode_queue_event(inode, IN_CREATE, 0, dentry->d_name.name,
 				  dentry->d_inode);
 	audit_inode_child(dentry->d_name.name, dentry, inode);
+
+	fsnotify(inode, FS_CREATE, dentry->d_inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -120,6 +141,8 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode, struct
 				  inode);
 	fsnotify_link_count(inode);
 	audit_inode_child(new_dentry->d_name.name, new_dentry, dir);
+
+	fsnotify(dir, FS_CREATE, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -131,6 +154,8 @@ static inline void fsnotify_mkdir(struct inode *inode, struct dentry *dentry)
 	inotify_inode_queue_event(inode, IN_CREATE | IN_ISDIR, 0, 
 				  dentry->d_name.name, dentry->d_inode);
 	audit_inode_child(dentry->d_name.name, dentry, inode);
+
+	fsnotify(inode, FS_CREATE | FS_IN_ISDIR, dentry->d_inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -139,14 +164,16 @@ static inline void fsnotify_mkdir(struct inode *inode, struct dentry *dentry)
 static inline void fsnotify_access(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
-	u32 mask = IN_ACCESS;
+	__u32 mask = FS_ACCESS;
 
 	if (S_ISDIR(inode->i_mode))
-		mask |= IN_ISDIR;
+		mask |= FS_IN_ISDIR;
 
 	dnotify_parent(dentry, DN_ACCESS);
 	inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
 	inotify_inode_queue_event(inode, mask, 0, NULL, NULL);
+
+	fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -155,14 +182,16 @@ static inline void fsnotify_access(struct dentry *dentry)
 static inline void fsnotify_modify(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
-	u32 mask = IN_MODIFY;
+	__u32 mask = FS_MODIFY;
 
 	if (S_ISDIR(inode->i_mode))
-		mask |= IN_ISDIR;
+		mask |= FS_IN_ISDIR;
 
 	dnotify_parent(dentry, DN_MODIFY);
 	inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
 	inotify_inode_queue_event(inode, mask, 0, NULL, NULL);
+
+	fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -171,13 +200,15 @@ static inline void fsnotify_modify(struct dentry *dentry)
 static inline void fsnotify_open(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
-	u32 mask = IN_OPEN;
+	__u32 mask = FS_OPEN;
 
 	if (S_ISDIR(inode->i_mode))
-		mask |= IN_ISDIR;
+		mask |= FS_IN_ISDIR;
 
 	inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
 	inotify_inode_queue_event(inode, mask, 0, NULL, NULL);
+
+	fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -189,13 +220,15 @@ static inline void fsnotify_close(struct file *file)
 	struct inode *inode = dentry->d_inode;
 	const char *name = dentry->d_name.name;
 	fmode_t mode = file->f_mode;
-	u32 mask = (mode & FMODE_WRITE) ? IN_CLOSE_WRITE : IN_CLOSE_NOWRITE;
+	__u32 mask = (mode & FMODE_WRITE) ? FS_CLOSE_WRITE : FS_CLOSE_NOWRITE;
 
 	if (S_ISDIR(inode->i_mode))
-		mask |= IN_ISDIR;
+		mask |= FS_IN_ISDIR;
 
 	inotify_dentry_parent_queue_event(dentry, mask, 0, name);
 	inotify_inode_queue_event(inode, mask, 0, NULL, NULL);
+
+	fsnotify(inode, mask, file, FSNOTIFY_EVENT_FILE);
 }
 
 /*
@@ -204,13 +237,15 @@ static inline void fsnotify_close(struct file *file)
 static inline void fsnotify_xattr(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
-	u32 mask = IN_ATTRIB;
+	__u32 mask = FS_ATTRIB;
 
 	if (S_ISDIR(inode->i_mode))
-		mask |= IN_ISDIR;
+		mask |= FS_IN_ISDIR;
 
 	inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
 	inotify_inode_queue_event(inode, mask, 0, NULL, NULL);
+
+	fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
 }
 
 /*
@@ -224,31 +259,31 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
 	u32 in_mask = 0;
 
 	if (ia_valid & ATTR_UID) {
-		in_mask |= IN_ATTRIB;
+		in_mask |= FS_ATTRIB;
 		dn_mask |= DN_ATTRIB;
 	}
 	if (ia_valid & ATTR_GID) {
-		in_mask |= IN_ATTRIB;
+		in_mask |= FS_ATTRIB;
 		dn_mask |= DN_ATTRIB;
 	}
 	if (ia_valid & ATTR_SIZE) {
-		in_mask |= IN_MODIFY;
+		in_mask |= FS_MODIFY;
 		dn_mask |= DN_MODIFY;
 	}
 	/* both times implies a utime(s) call */
 	if ((ia_valid & (ATTR_ATIME | ATTR_MTIME)) == (ATTR_ATIME | ATTR_MTIME))
 	{
-		in_mask |= IN_ATTRIB;
+		in_mask |= FS_ATTRIB;
 		dn_mask |= DN_ATTRIB;
 	} else if (ia_valid & ATTR_ATIME) {
-		in_mask |= IN_ACCESS;
+		in_mask |= FS_ACCESS;
 		dn_mask |= DN_ACCESS;
 	} else if (ia_valid & ATTR_MTIME) {
-		in_mask |= IN_MODIFY;
+		in_mask |= FS_MODIFY;
 		dn_mask |= DN_MODIFY;
 	}
 	if (ia_valid & ATTR_MODE) {
-		in_mask |= IN_ATTRIB;
+		in_mask |= FS_ATTRIB;
 		dn_mask |= DN_ATTRIB;
 	}
 
@@ -256,20 +291,40 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
 		dnotify_parent(dentry, dn_mask);
 	if (in_mask) {
 		if (S_ISDIR(inode->i_mode))
-			in_mask |= IN_ISDIR;
+			in_mask |= FS_IN_ISDIR;
 		inotify_inode_queue_event(inode, in_mask, 0, NULL, NULL);
 		inotify_dentry_parent_queue_event(dentry, in_mask, 0,
 						  dentry->d_name.name);
+		fsnotify(inode, in_mask, inode, FSNOTIFY_EVENT_INODE);
 	}
 }
 
-#ifdef CONFIG_INOTIFY	/* inotify helpers */
+#if defined(CONFIG_INOTIFY) || defined(CONFIG_FSNOTIFY)	/* notify helpers */
 
 /*
  * fsnotify_oldname_init - save off the old filename before we change it
  */
 static inline const char *fsnotify_oldname_init(const char *name)
 {
+	BUILD_BUG_ON(IN_ACCESS != FS_ACCESS);
+	BUILD_BUG_ON(IN_MODIFY != FS_MODIFY);
+	BUILD_BUG_ON(IN_ATTRIB != FS_ATTRIB);
+	BUILD_BUG_ON(IN_CLOSE_WRITE != FS_CLOSE_WRITE);
+	BUILD_BUG_ON(IN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
+	BUILD_BUG_ON(IN_OPEN != FS_OPEN);
+	BUILD_BUG_ON(IN_MOVED_FROM != FS_MOVED_FROM);
+	BUILD_BUG_ON(IN_MOVED_TO != FS_MOVED_TO);
+	BUILD_BUG_ON(IN_CREATE != FS_CREATE);
+	BUILD_BUG_ON(IN_DELETE != FS_DELETE);
+	BUILD_BUG_ON(IN_DELETE_SELF != FS_DELETE_SELF);
+	BUILD_BUG_ON(IN_MOVE_SELF != FS_MOVE_SELF);
+	BUILD_BUG_ON(IN_Q_OVERFLOW != FS_Q_OVERFLOW);
+
+	BUILD_BUG_ON(IN_UNMOUNT != FS_UNMOUNT);
+	BUILD_BUG_ON(IN_ISDIR != FS_IN_ISDIR);
+	BUILD_BUG_ON(IN_IGNORED != FS_IN_IGNORED);
+	BUILD_BUG_ON(IN_ONESHOT != FS_IN_ONESHOT);
+
 	return kstrdup(name, GFP_KERNEL);
 }
 
@@ -281,7 +336,7 @@ static inline void fsnotify_oldname_free(const char *old_name)
 	kfree(old_name);
 }
 
-#else	/* CONFIG_INOTIFY */
+#else	/* CONFIG_INOTIFY || CONFIG_FSNOTIFY */
 
 static inline const char *fsnotify_oldname_init(const char *name)
 {
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
new file mode 100644
index 0000000..0523333
--- /dev/null
+++ b/include/linux/fsnotify_backend.h
@@ -0,0 +1,135 @@
+/*
+ * Filesystem access notification for Linux
+ *
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@...hat.com>
+ */
+
+#ifndef _LINUX_FSNOTIFY_BACKEND_H
+#define _LINUX_FSNOTIFY_BACKEND_H
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h> /* struct inode */
+#include <linux/list.h>
+#include <linux/path.h> /* struct path */
+#include <linux/spinlock.h>
+#include <linux/wait.h>
+
+#include <asm/atomic.h>
+
+/*
+ * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
+ * convert between them.  dnotify only needs conversion at watch creation
+ * so no perf loss there.  fanotify isn't defined yet, so it can use the
+ * wholes if it needs more events.
+ */
+#define FS_ACCESS		0x00000001ul	/* File was accessed */
+#define FS_MODIFY		0x00000002ul	/* File was modified */
+#define FS_ATTRIB		0x00000004ul	/* Metadata changed */
+#define FS_CLOSE_WRITE		0x00000008ul	/* Writtable file was closed */
+#define FS_CLOSE_NOWRITE	0x00000010ul	/* Unwrittable file closed */
+#define FS_OPEN			0x00000020ul	/* File was opened */
+#define FS_MOVED_FROM		0x00000040ul	/* File was moved from X */
+#define FS_MOVED_TO		0x00000080ul	/* File was moved to Y */
+#define FS_CREATE		0x00000100ul	/* Subfile was created */
+#define FS_DELETE		0x00000200ul	/* Subfile was deleted */
+#define FS_DELETE_SELF		0x00000400ul	/* Self was deleted */
+#define FS_MOVE_SELF		0x00000800ul	/* Self was moved */
+
+#define FS_UNMOUNT		0x00002000ul	/* inode on umount fs */
+#define FS_Q_OVERFLOW		0x00004000ul	/* Event queued overflowed */
+#define FS_IN_IGNORED		0x00008000ul	/* last inotify event here */
+
+#define FS_IN_ISDIR		0x40000000ul	/* event occurred against dir */
+#define FS_IN_ONESHOT		0x80000000ul	/* only send event once */
+
+#define FS_DN_RENAME		0x10000000ul	/* file renamed */
+#define FS_DN_MULTISHOT		0x20000000ul	/* dnotify multishot */
+
+#define FS_EVENT_ON_CHILD	0x08000000ul
+
+struct fsnotify_group;
+struct fsnotify_event;
+
+/*
+ * Each group much define these ops.
+ *
+ * handle_event - main call for a group to handle an fs event
+ * free_group_priv - called when a group refcnt hits 0 to clean up the private union
+ */
+struct fsnotify_ops {
+	int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
+	void (*free_group_priv)(struct fsnotify_group *group);
+};
+
+/*
+ * A group is a "thing" that wants to receive notification about filesystem
+ * events.  The mask holds the subset of event types this group cares about.
+ * refcnt on a group is up to the implementor and at any moment if it goes 0
+ * everything will be cleaned up.
+ */
+struct fsnotify_group {
+	struct list_head group_list;	/* list of all groups on the system */
+	__u32 mask;			/* mask of events this group cares about */
+	atomic_t refcnt;		/* num of processes with a special file open */
+	unsigned int group_num;		/* the 'name' of the event */
+
+	const struct fsnotify_ops *ops;	/* how this group handles things */
+
+	unsigned int evicted:1;		/* has this group been evicted? */
+
+	/* groups can define private fields here */
+	union {
+	};
+};
+
+/*
+ * all of the information about the original object we want to now send to
+ * a group.  If you want to carry more info from the accessing task to the
+ * listener this structure is where you need to be adding fields.
+ */
+struct fsnotify_event {
+	spinlock_t lock;	/* protection for the associated event_holder and private_list */
+	struct inode *to_tell;
+	/*
+	 * depending on the event type we should have either a path or inode
+	 * we should never have more than one....
+	 */
+	union {
+		struct path path;
+		struct inode *inode;
+	};
+/* when calling fsnotify tell it if the data is a path or inode */
+#define FSNOTIFY_EVENT_PATH	1
+#define FSNOTIFY_EVENT_INODE	2
+#define FSNOTIFY_EVENT_FILE	3
+	int data_type;		/* which of the above union we have */
+	atomic_t refcnt;	/* how many groups still are using/need to send this event */
+	__u32 mask;		/* the type of access */
+};
+
+#ifdef CONFIG_FSNOTIFY
+
+/* called from the vfs to signal fs events */
+extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
+
+/* called from fsnotify interfaces, such as fanotify or dnotify */
+extern void fsnotify_recalc_global_mask(void);
+extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask, const struct fsnotify_ops *ops);
+extern void fsnotify_put_group(struct fsnotify_group *group);
+
+extern void fsnotify_get_event(struct fsnotify_event *event);
+extern void fsnotify_put_event(struct fsnotify_event *event);
+extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event);
+
+/* put here because inotify does some weird stuff when destroying watches */
+extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, int data_is);
+#else
+
+static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
+{}
+#endif	/* CONFIG_FSNOTIFY */
+
+#endif	/* __KERNEL __ */
+
+#endif	/* _LINUX_FSNOTIFY_BACKEND_H */

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