fanotify: convert access_mutex to spinlock

access_mutex is used only to guard operations on access_list.  There's
no need for sleeping within this lock so just make a spinlock out of it.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 8f5e852..2a57278 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -134,7 +134,7 @@ static struct fanotify_perm_event_info *dequeue_event(
 {
        struct fanotify_perm_event_info *event, *return_e = NULL;
 
-       mutex_lock(&group->fanotify_data.access_mutex);
+       spin_lock(&group->fanotify_data.access_lock);
        list_for_each_entry(event, &group->fanotify_data.access_list,
                            fae.fse.list) {
                if (event->fd != fd)
@@ -144,7 +144,7 @@ static struct fanotify_perm_event_info *dequeue_event(
                return_e = event;
                break;
        }
-       mutex_unlock(&group->fanotify_data.access_mutex);
+       spin_unlock(&group->fanotify_data.access_lock);
 
        pr_debug("%s: found return_re=%p\n", __func__, return_e);
 
@@ -213,10 +213,10 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 
                pevent = FANOTIFY_PE(event);
                pevent->fd = fd;
-               mutex_lock(&group->fanotify_data.access_mutex);
+               spin_lock(&group->fanotify_data.access_lock);
                list_add_tail(&pevent->fae.fse.list,
                              &group->fanotify_data.access_list);
-               mutex_unlock(&group->fanotify_data.access_mutex);
+               spin_unlock(&group->fanotify_data.access_lock);
        }
 #endif
 
@@ -346,7 +346,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
        struct fanotify_perm_event_info *event, *next;
 
-       mutex_lock(&group->fanotify_data.access_mutex);
+       spin_lock(&group->fanotify_data.access_lock);
 
        atomic_inc(&group->fanotify_data.bypass_perm);
 
@@ -358,7 +358,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
                list_del_init(&event->fae.fse.list);
                event->response = FAN_ALLOW;
        }
-       mutex_unlock(&group->fanotify_data.access_mutex);
+       spin_unlock(&group->fanotify_data.access_lock);
 
        wake_up(&group->fanotify_data.access_waitq);
 #endif
@@ -700,7 +700,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 
        group->fanotify_data.f_flags = event_f_flags;
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-       mutex_init(&group->fanotify_data.access_mutex);
+       spin_lock_init(&group->fanotify_data.access_lock);
        init_waitqueue_head(&group->fanotify_data.access_waitq);
        INIT_LIST_HEAD(&group->fanotify_data.access_list);
        atomic_set(&group->fanotify_data.bypass_perm, 0);

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 64cf3ef..fc7718c 100644 (file)
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -178,7 +178,7 @@ struct fsnotify_group {
                struct fanotify_group_private_data {
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
                        /* allows a group to block waiting for a userspace response */
-                       struct mutex access_mutex;
+                       spinlock_t access_lock;
                        struct list_head access_list;
                        wait_queue_head_t access_waitq;
                        atomic_t bypass_perm;