[PATCH] device-mapper: store bdev while frozen

Store the struct block_device while device is frozen, saving us one call to
bdget_disk().

Signed-Off-By: Alasdair G Kergon <agk@redhat.com>
From: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 15 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 243ff6884e83..ea180af6d227 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -97,6 +97,7 @@ struct mapped_device {
          * freeze/thaw support require holding onto a super block
          */
         struct super_block *frozen_sb;
+        struct block_device *frozen_bdev;
 };
 
 #define MIN_IOS 256
@@ -990,19 +991,17 @@ int dm_swap_table(struct mapped_device *md, struct dm_table *table)
  */
 static int __lock_fs(struct mapped_device *md)
 {
-        struct block_device *bdev;
-
         if (test_and_set_bit(DMF_FS_LOCKED, &md->flags))
                 return 0;
 
-        bdev = bdget_disk(md->disk, 0);
-        if (!bdev) {
+        md->frozen_bdev = bdget_disk(md->disk, 0);
+        if (!md->frozen_bdev) {
                 DMWARN("bdget failed in __lock_fs");
                 return -ENOMEM;
         }
 
         WARN_ON(md->frozen_sb);
-        md->frozen_sb = freeze_bdev(bdev);
+        md->frozen_sb = freeze_bdev(md->frozen_bdev);
         /* don't bdput right now, we don't want the bdev
          * to go away while it is locked.  We'll bdput
          * in __unlock_fs
@@ -1012,21 +1011,15 @@ static int __lock_fs(struct mapped_device *md)
 
 static int __unlock_fs(struct mapped_device *md)
 {
-        struct block_device *bdev;
-
         if (!test_and_clear_bit(DMF_FS_LOCKED, &md->flags))
                 return 0;
 
-        bdev = bdget_disk(md->disk, 0);
-        if (!bdev) {
-                DMWARN("bdget failed in __unlock_fs");
-                return -ENOMEM;
-        }
+        thaw_bdev(md->frozen_bdev, md->frozen_sb);
+        bdput(md->frozen_bdev);
 
-        thaw_bdev(bdev, md->frozen_sb);
         md->frozen_sb = NULL;
-        bdput(bdev);
-        bdput(bdev);
+        md->frozen_bdev = NULL;
+
         return 0;
 }