block: don't grab block_class_lock unnecessarily

block_class_lock protects major_names array and bdev_map and doesn't
have anything to do with block class devices.  Don't grab them while
iterating over block class devices.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 9 insertions, 19 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 0be95135c404..9eb8b3e212c1 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -283,9 +283,7 @@ static int printk_partition(struct device *dev, void *data)
  */
 void __init printk_all_partitions(void)
 {
-        mutex_lock(&block_class_lock);
         class_for_each_device(&block_class, NULL, NULL, printk_partition);
-        mutex_unlock(&block_class_lock);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -305,17 +303,15 @@ static int find_start(struct device *dev, void *data)
 static void *part_start(struct seq_file *part, loff_t *pos)
 {
         struct device *dev;
-        loff_t k = *pos;
+        loff_t n = *pos;
 
-        if (!k)
+        if (!n)
                 part->private = (void *)1LU;    /* tell show to print header */
 
-        mutex_lock(&block_class_lock);
-        dev = class_find_device(&block_class, NULL, &k, find_start);
-        if (dev) {
-                put_device(dev);
+        dev = class_find_device(&block_class, NULL, &n, find_start);
+        if (dev)
                 return dev_to_disk(dev);
-        }
+
         return NULL;
 }
 
@@ -341,7 +337,6 @@ static void *part_next(struct seq_file *part, void *v, loff_t *pos)
 
 static void part_stop(struct seq_file *part, void *v)
 {
-        mutex_unlock(&block_class_lock);
 }
 
 static int show_partition(struct seq_file *part, void *v)
@@ -583,14 +578,12 @@ static struct device_type disk_type = {
 static void *diskstats_start(struct seq_file *part, loff_t *pos)
 {
         struct device *dev;
-        loff_t k = *pos;
+        loff_t n = *pos;
 
-        mutex_lock(&block_class_lock);
-        dev = class_find_device(&block_class, NULL, &k, find_start);
-        if (dev) {
-                put_device(dev);
+        dev = class_find_device(&block_class, NULL, &n, find_start);
+        if (dev)
                 return dev_to_disk(dev);
-        }
+
         return NULL;
 }
 
@@ -610,7 +603,6 @@ static void *diskstats_next(struct seq_file *part, void *v, loff_t *pos)
 
 static void diskstats_stop(struct seq_file *part, void *v)
 {
-        mutex_unlock(&block_class_lock);
 }
 
 static int diskstats_show(struct seq_file *s, void *v)
@@ -729,7 +721,6 @@ dev_t blk_lookup_devt(const char *name, int part)
         dev_t devt = MKDEV(0, 0);
         struct find_block find;
 
-        mutex_lock(&block_class_lock);
         find.name = name;
         find.part = part;
         dev = class_find_device(&block_class, NULL, &find, match_id);
@@ -738,7 +729,6 @@ dev_t blk_lookup_devt(const char *name, int part)
                 devt = MKDEV(MAJOR(dev->devt),
                              MINOR(dev->devt) + part);
         }
-        mutex_unlock(&block_class_lock);
 
         return devt;
 }