hfs: get rid of lock_super

Stop using lock_super for serializing the MDB changes - use the buffer-head own
lock instead. Tested with fsstress.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/hfs/mdb.c

@@ -260,7 +260,7 @@ void hfs_mdb_commit(struct super_block *sb)
 {
 	struct hfs_mdb *mdb = HFS_SB(sb)->mdb;
 
-	lock_super(sb);
+	lock_buffer(HFS_SB(sb)->mdb_bh);
 	if (test_and_clear_bit(HFS_FLG_MDB_DIRTY, &HFS_SB(sb)->flags)) {
 		/* These parameters may have been modified, so write them back */
 		mdb->drLsMod = hfs_mtime();
@@ -284,9 +284,13 @@ void hfs_mdb_commit(struct super_block *sb)
 				     &mdb->drXTFlSize, NULL);
 		hfs_inode_write_fork(HFS_SB(sb)->cat_tree->inode, mdb->drCTExtRec,
 				     &mdb->drCTFlSize, NULL);
+
+		lock_buffer(HFS_SB(sb)->alt_mdb_bh);
 		memcpy(HFS_SB(sb)->alt_mdb, HFS_SB(sb)->mdb, HFS_SECTOR_SIZE);
 		HFS_SB(sb)->alt_mdb->drAtrb |= cpu_to_be16(HFS_SB_ATTRIB_UNMNT);
 		HFS_SB(sb)->alt_mdb->drAtrb &= cpu_to_be16(~HFS_SB_ATTRIB_INCNSTNT);
+		unlock_buffer(HFS_SB(sb)->alt_mdb_bh);
+
 		mark_buffer_dirty(HFS_SB(sb)->alt_mdb_bh);
 		sync_dirty_buffer(HFS_SB(sb)->alt_mdb_bh);
 	}
@@ -309,7 +313,11 @@ void hfs_mdb_commit(struct super_block *sb)
 				break;
 			}
 			len = min((int)sb->s_blocksize - off, size);
+
+			lock_buffer(bh);
 			memcpy(bh->b_data + off, ptr, len);
+			unlock_buffer(bh);
+
 			mark_buffer_dirty(bh);
 			brelse(bh);
 			block++;
@@ -318,7 +326,7 @@ void hfs_mdb_commit(struct super_block *sb)
 			size -= len;
 		}
 	}
-	unlock_super(sb);
+	unlock_buffer(HFS_SB(sb)->mdb_bh);
 }
 
 void hfs_mdb_close(struct super_block *sb)