fs/block_dev.c: __read_mostly improvement and sb_is_blkdev_sb utilization

- iget5_locked in bdget really needs blockdev_superblock, instead of
  bd_mnt, so bd_mnt could be just a local variable;

- blockdev_superblock really needs __read_mostly, while local var bd_mnt
  not;

- make use of sb_is_blkdev_sb in bd_forget, instead of direct reference
  to blockdev_superblock.

Signed-off-by: Denis ChengRq <crquan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 99e0ae1a4c78..349a26c10001 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -326,12 +326,13 @@ static struct file_system_type bd_type = {
         .kill_sb        = kill_anon_super,
 };
 
-static struct vfsmount *bd_mnt __read_mostly;
-struct super_block *blockdev_superblock;
+struct super_block *blockdev_superblock __read_mostly;
 
 void __init bdev_cache_init(void)
 {
         int err;
+        struct vfsmount *bd_mnt;
+
         bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
                         0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                                 SLAB_MEM_SPREAD|SLAB_PANIC),
@@ -373,7 +374,7 @@ struct block_device *bdget(dev_t dev)
         struct block_device *bdev;
         struct inode *inode;
 
-        inode = iget5_locked(bd_mnt->mnt_sb, hash(dev),
+        inode = iget5_locked(blockdev_superblock, hash(dev),
                         bdev_test, bdev_set, &dev);
 
         if (!inode)
@@ -463,7 +464,7 @@ void bd_forget(struct inode *inode)
 
         spin_lock(&bdev_lock);
         if (inode->i_bdev) {
-                if (inode->i_sb != blockdev_superblock)
+                if (!sb_is_blkdev_sb(inode->i_sb))
                         bdev = inode->i_bdev;
                 __bd_forget(inode);
         }