[PATCH] BLOCK: Remove dependence on existence of blockdev_superblock [try #6]

Move blockdev_superblock extern declaration from fs/fs-writeback.c to a
headerfile and remove the dependence on it by wrapping it in a macro.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 5 insertions, 3 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 0639024d83a9..c403b66ec83c 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -319,7 +319,7 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
 
                 if (!bdi_cap_writeback_dirty(bdi)) {
                         list_move(&inode->i_list, &sb->s_dirty);
-                        if (sb == blockdev_superblock) {
+                        if (sb_is_blkdev_sb(sb)) {
                                 /*
                                  * Dirty memory-backed blockdev: the ramdisk
                                  * driver does this.  Skip just this inode
@@ -336,14 +336,14 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
 
                 if (wbc->nonblocking && bdi_write_congested(bdi)) {
                         wbc->encountered_congestion = 1;
-                        if (sb != blockdev_superblock)
+                        if (!sb_is_blkdev_sb(sb))
                                 break;          /* Skip a congested fs */
                         list_move(&inode->i_list, &sb->s_dirty);
                         continue;               /* Skip a congested blockdev */
                 }
 
                 if (wbc->bdi && bdi != wbc->bdi) {
-                        if (sb != blockdev_superblock)
+                        if (!sb_is_blkdev_sb(sb))
                                 break;          /* fs has the wrong queue */
                         list_move(&inode->i_list, &sb->s_dirty);
                         continue;               /* blockdev has wrong queue */
diff --git a/fs/internal.h b/fs/internal.h
index c21ecd37b1e7..f662b703bb97 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -17,6 +17,8 @@
 extern struct super_block *blockdev_superblock;
 extern void __init bdev_cache_init(void);
 
+#define sb_is_blkdev_sb(sb) ((sb) == blockdev_superblock)
+
 /*
  * char_dev.c
  */