[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>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/inotify.c b/fs/inotify.c
index 2e4e2a57708c..2fd97ef547ff 100644
--- 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),