[PATCH] inotify speedup

Bypass an inotify-related fastpath spinlock and several function calls on
systems which have no inotify watches registered.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/inotify.c b/fs/inotify.c
index 2e4e2a57708cf95dcdf348235376ef901f4dc295..2fd97ef547ffcac2b35a3bcee5a37667b8e51ef4 100644 (file)
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -37,6 +37,7 @@
 #include <asm/ioctls.h>
 
 static atomic_t inotify_cookie;
+static atomic_t inotify_watches;
 
 static kmem_cache_t *watch_cachep;
 static kmem_cache_t *event_cachep;
@@ -422,6 +423,7 @@ static struct inotify_watch *create_watch(struct inotify_device *dev,
        get_inotify_watch(watch);
 
        atomic_inc(&dev->user->inotify_watches);
+       atomic_inc(&inotify_watches);
 
        return watch;
 }
@@ -454,6 +456,7 @@ static void remove_watch_no_event(struct inotify_watch *watch,
        list_del(&watch->d_list);
 
        atomic_dec(&dev->user->inotify_watches);
+       atomic_dec(&inotify_watches);
        idr_remove(&dev->idr, watch->wd);
        put_inotify_watch(watch);
 }
@@ -532,6 +535,9 @@ void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
        struct dentry *parent;
        struct inode *inode;
 
+       if (!atomic_read (&inotify_watches))
+               return;
+
        spin_lock(&dentry->d_lock);
        parent = dentry->d_parent;
        inode = parent->d_inode;
@@ -1043,6 +1049,7 @@ static int __init inotify_setup(void)
        inotify_max_user_watches = 8192;
 
        atomic_set(&inotify_cookie, 0);
+       atomic_set(&inotify_watches, 0);
 
        watch_cachep = kmem_cache_create("inotify_watch_cache",
                                         sizeof(struct inotify_watch),