ext4: Support large files

This patch converts ext4_inode i_blocks to represent total
blocks occupied by the inode in file system block size.
Earlier the variable used to represent this in 512 byte
block size. This actually limited the total size of the file.

The feature is enabled transparently when we write an inode
whose i_blocks cannot be represnted as 512 byte units in a
48 bit variable.

inode flag  EXT4_HUGE_FILE_FL

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2b9dc96..64067de 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1631,11 +1631,14 @@
 		upper_limit >>= (bits - 9);
 
 	} else {
-		/* We use 48 bit ext4_inode i_blocks */
+		/*
+		 * We use 48 bit ext4_inode i_blocks
+		 * With EXT4_HUGE_FILE_FL set the i_blocks
+		 * represent total number of blocks in
+		 * file system block size
+		 */
 		upper_limit = (1LL << 48) - 1;
 
-		/* total blocks in file system block size */
-		upper_limit >>= (bits - 9);
 	}
 
 	/* indirect blocks */