dm: remove dm_mutex after bkl conversion

This patch replaces dm_mutex with _minor_lock in dm_blk_close()
and then removes it.

During the BKL conversion, commit 6e9624b8caec290d28b4c6d9ec75749df6372b87
(block: push down BKL into .open and .release) pushed lock_kernel()
down into dm_blk_open/close calls.
Commit 2a48fc0ab24241755dc93bfd4f01d68efab47f5a
(block: autoconvert trivial BKL users to private mutex) converted it to a
local mutex, but _minor_lock is sufficient.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4ef066a3090f..0de692176ad4 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -32,7 +32,6 @@
 #define DM_COOKIE_ENV_VAR_NAME "DM_COOKIE"
 #define DM_COOKIE_LENGTH 24
 
-static DEFINE_MUTEX(dm_mutex);
 static const char *_name = DM_NAME;
 
 static unsigned int major = 0;
@@ -328,7 +327,6 @@ static int dm_blk_open(struct block_device *bdev, fmode_t mode)
 {
         struct mapped_device *md;
 
-        mutex_lock(&dm_mutex);
         spin_lock(&_minor_lock);
 
         md = bdev->bd_disk->private_data;
@@ -346,7 +344,6 @@ static int dm_blk_open(struct block_device *bdev, fmode_t mode)
 
 out:
         spin_unlock(&_minor_lock);
-        mutex_unlock(&dm_mutex);
 
         return md ? 0 : -ENXIO;
 }
@@ -355,10 +352,12 @@ static int dm_blk_close(struct gendisk *disk, fmode_t mode)
 {
         struct mapped_device *md = disk->private_data;
 
-        mutex_lock(&dm_mutex);
+        spin_lock(&_minor_lock);
+
         atomic_dec(&md->open_count);
         dm_put(md);
-        mutex_unlock(&dm_mutex);
+
+        spin_unlock(&_minor_lock);
 
         return 0;
 }