ext4: replace MAX_DEFRAG_SIZE with EXT_MAX_BLOCK

There's no reason to redefine the maximum allowable offset
in an extent-based file just for defrag; 
EXT_MAX_BLOCK already does this.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -476,7 +476,6 @@ struct move_extent {
 	__u64 len;		/* block length to be moved */
 	__u64 moved_len;	/* moved block length */
 };
-#define MAX_DEFRAG_SIZE         ((1UL<<31) - 1)
 
 #define EXT4_EPOCH_BITS 2
 #define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)

fs/ext4/ext4_extents.h

@@ -137,6 +137,7 @@ typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *,
 #define EXT_BREAK      1
 #define EXT_REPEAT     2
 
+/* Maximum logical block in a file; ext4_extent's ee_block is __le32 */
 #define EXT_MAX_BLOCK	0xffffffff
 
 /*

fs/ext4/move_extent.c

@@ -1040,12 +1040,12 @@ mext_check_arguments(struct inode *orig_inode,
 		return -EINVAL;
 	}
 
-	if ((orig_start > MAX_DEFRAG_SIZE) ||
-	    (donor_start > MAX_DEFRAG_SIZE) ||
-	    (*len > MAX_DEFRAG_SIZE) ||
-	    (orig_start + *len > MAX_DEFRAG_SIZE))  {
-		ext4_debug("ext4 move extent: Can't handle over [%lu] blocks "
-			"[ino:orig %lu, donor %lu]\n", MAX_DEFRAG_SIZE,
+	if ((orig_start > EXT_MAX_BLOCK) ||
+	    (donor_start > EXT_MAX_BLOCK) ||
+	    (*len > EXT_MAX_BLOCK) ||
+	    (orig_start + *len > EXT_MAX_BLOCK))  {
+		ext4_debug("ext4 move extent: Can't handle over [%u] blocks "
+			"[ino:orig %lu, donor %lu]\n", EXT_MAX_BLOCK,
 			orig_inode->i_ino, donor_inode->i_ino);
 		return -EINVAL;
 	}