Merge tag 'v3.10.92' into update

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / block / elevator.c

diff --git a/block/elevator.c b/block/elevator.c
index 668394d185885bc3fcc878697878a4cb07be899e..6d765f7e2b2bd905984ee54fc4dde56d1f5d1744 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -186,6 +186,12 @@ int elevator_init(struct request_queue *q, char *name)
        struct elevator_type *e = NULL;
        int err;
 
+       /*
+        * q->sysfs_lock must be held to provide mutual exclusion between
+        * elevator_switch() and here.
+        */
+       lockdep_assert_held(&q->sysfs_lock);
+
        if (unlikely(q->elevator))
                return 0;
 
@@ -959,7 +965,7 @@ fail_init:
 /*
  * Switch this queue to the given IO scheduler.
  */
-int elevator_change(struct request_queue *q, const char *name)
+static int __elevator_change(struct request_queue *q, const char *name)
 {
        char elevator_name[ELV_NAME_MAX];
        struct elevator_type *e;
@@ -981,6 +987,18 @@ int elevator_change(struct request_queue *q, const char *name)
 
        return elevator_switch(q, e);
 }
+
+int elevator_change(struct request_queue *q, const char *name)
+{
+       int ret;
+
+       /* Protect q->elevator from elevator_init() */
+       mutex_lock(&q->sysfs_lock);
+       ret = __elevator_change(q, name);
+       mutex_unlock(&q->sysfs_lock);
+
+       return ret;
+}
 EXPORT_SYMBOL(elevator_change);
 
 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
@@ -991,7 +1009,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
        if (!q->elevator)
                return count;
 
-       ret = elevator_change(q, name);
+       ret = __elevator_change(q, name);
        if (!ret)
                return count;