7 files changed, 448 insertions, 0 deletions

diff --git a/fs/notify/Kconfig b/fs/notify/Kconfig
index 50914d7303c6..31dac7e3b0f1 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 5a95b6010ce7..db5467b5b58d 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 000000000000..56bee0f10c38
--- /dev/null
+++ b/fs/notify/fsnotify.c
@@ -0,0 +1,79 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.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 000000000000..c6a8bd476572
--- /dev/null
+++ b/fs/notify/fsnotify.h
@@ -0,0 +1,15 @@
+#ifndef __FS_NOTIFY_FSNOTIFY_H_
+#define __FS_NOTIFY_FSNOTIFY_H_
+
+#include <linux/list.h>
+#include <linux/fsnotify.h>
+#include <linux/srcu.h>
+#include <linux/types.h>
+
+/* protects reads of fsnotify_groups */
+extern struct srcu_struct fsnotify_grp_srcu;
+/* all groups which receive fsnotify events */
+extern struct list_head fsnotify_groups;
+/* all bitwise OR of all event types (FS_*) for all fsnotify_groups */
+extern __u32 fsnotify_mask;
+#endif  /* __FS_NOTIFY_FSNOTIFY_H_ */
diff --git a/fs/notify/group.c b/fs/notify/group.c
new file mode 100644
index 000000000000..c6812953b968
--- /dev/null
+++ b/fs/notify/group.c
@@ -0,0 +1,198 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.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>
+
+/* protects writes to fsnotify_groups and fsnotify_mask */
+static DEFINE_MUTEX(fsnotify_grp_mutex);
+/* protects reads while running the fsnotify_groups list */
+struct srcu_struct fsnotify_grp_srcu;
+/* all groups registered to receive filesystem notifications */
+LIST_HEAD(fsnotify_groups);
+/* bitwise OR of all events (FS_*) interesting to some group on this system */
+__u32 fsnotify_mask;
+
+/*
+ * When a new group registers or changes it's set of interesting events
+ * this function updates the fsnotify_mask to contain all interesting events
+ */
+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;
+}
+
+/*
+ * Take a reference to a group so things found under the fsnotify_grp_mutex
+ * can't get freed under us
+ */
+static void fsnotify_get_group(struct fsnotify_group *group)
+{
+        atomic_inc(&group->refcnt);
+}
+
+/*
+ * Final freeing of a group
+ */
+static void fsnotify_destroy_group(struct fsnotify_group *group)
+{
+        if (group->ops->free_group_priv)
+                group->ops->free_group_priv(group);
+
+        kfree(group);
+}
+
+/*
+ * Remove this group from the global list of groups that will get events
+ * this can be done even if there are still references and things still using
+ * this group.  This just stops the group from getting new events.
+ */
+static void __fsnotify_evict_group(struct fsnotify_group *group)
+{
+        BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
+
+        if (group->on_group_list)
+                list_del_rcu(&group->group_list);
+        group->on_group_list = 0;
+}
+
+/*
+ * Called when a group is no longer interested in getting events.  This can be
+ * used if a group is misbehaving or if for some reason a group should no longer
+ * get any filesystem events.
+ */
+void fsnotify_evict_group(struct fsnotify_group *group)
+{
+        mutex_lock(&fsnotify_grp_mutex);
+        __fsnotify_evict_group(group);
+        mutex_unlock(&fsnotify_grp_mutex);
+}
+
+/*
+ * Drop a reference to a group.  Free it if it's through.
+ */
+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 access....
+         */
+        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);
+}
+
+/*
+ * Simply run the fsnotify_groups list and find a group which matches
+ * the given parameters.  If a group is found we take a reference to that
+ * 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.
+ */
+struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
+                                             const struct fsnotify_ops *ops)
+{
+        struct fsnotify_group *group, *tgroup;
+
+        /* very low use, simpler locking if we just always alloc */
+        group = kmalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
+        if (!group)
+                return ERR_PTR(-ENOMEM);
+
+        atomic_set(&group->refcnt, 1);
+
+        group->on_group_list = 0;
+        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 */
+        list_add_rcu(&group->group_list, &fsnotify_groups);
+        group->on_group_list = 1;
+
+        mutex_unlock(&fsnotify_grp_mutex);
+
+        if (mask)
+                fsnotify_recalc_global_mask();
+
+        return group;
+}
diff --git a/fs/notify/inotify/inotify.c b/fs/notify/inotify/inotify.c
index 220c13f0d73d..40b1cf914ccb 100644
--- a/fs/notify/inotify/inotify.c
+++ b/fs/notify/inotify/inotify.c
@@ -32,6 +32,7 @@
 #include <linux/list.h>
 #include <linux/writeback.h>
 #include <linux/inotify.h>
+#include <linux/fsnotify_backend.h>
 
 static atomic_t inotify_cookie;
 
@@ -905,6 +906,25 @@ EXPORT_SYMBOL_GPL(inotify_rm_watch);
  */
 static int __init inotify_setup(void)
 {
+        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);
+
         atomic_set(&inotify_cookie, 0);
 
         return 0;
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
new file mode 100644
index 000000000000..b8e9a87f8f58
--- /dev/null
+++ b/fs/notify/notification.c
@@ -0,0 +1,121 @@
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.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 *fsnotify_event_cachep;
+
+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);
+
+                kmem_cache_free(fsnotify_event_cachep, event);
+        }
+}
+
+/*
+ * Allocate a new event which will be sent to each group's handle_event function
+ * if the group was interested in this particular 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(fsnotify_event_cachep, 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;
+        case FSNOTIFY_EVENT_NONE:
+                event->inode = NULL;
+                event->path.dentry = NULL;
+                event->path.mnt = NULL;
+                break;
+        default:
+                BUG();
+        }
+
+        event->mask = mask;
+
+        return event;
+}
+
+__init int fsnotify_notification_init(void)
+{
+        fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
+
+        return 0;
+}
+subsys_initcall(fsnotify_notification_init);
+