ext4: Introduce ext4_lblk_t

This patch adds a new data type ext4_lblk_t to represent
the logical file blocks.

This is the preparatory patch to support large files in ext4
The follow up patch with convert the ext4_inode i_blocks to
represent the number of blocks in file system block size. This
changes makes it possible to have a block number 2**32 -1 which
will result in overflow if the block number is represented by
signed long. This patch convert all the block number to type
ext4_lblk_t which is typedef to __u32

Also remove dead code ext4_ext_walk_space

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ab7010d..6302b03 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2914,7 +2914,7 @@
 			       size_t len, loff_t off)
 {
 	struct inode *inode = sb_dqopt(sb)->files[type];
-	sector_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
+	ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
 	int err = 0;
 	int offset = off & (sb->s_blocksize - 1);
 	int tocopy;
@@ -2952,7 +2952,7 @@
 				const char *data, size_t len, loff_t off)
 {
 	struct inode *inode = sb_dqopt(sb)->files[type];
-	sector_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
+	ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
 	int err = 0;
 	int offset = off & (sb->s_blocksize - 1);
 	int tocopy;