ext4: fix the comment describing ext4_ext_search_right()

The comment describing what ext4_ext_search_right() does is incorrect.
We return 0 in *phys when *logical is the 'largest' allocated block,
not smallest.  

Fix a few other typos while we're at it.

Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>

fs/ext4/extents.c

@@ -1263,7 +1263,7 @@ static int ext4_ext_search_left(struct inode *inode,
 /*
  * search the closest allocated block to the right for *logical
  * and returns it at @logical + it's physical address at @phys
- * if *logical is the smallest allocated block, the function
+ * if *logical is the largest allocated block, the function
  * returns 0 at @phys
  * return value contains 0 (success) or error code
  */
@@ -2168,7 +2168,7 @@ int ext4_ext_calc_credits_for_single_extent(struct inode *inode, int nrblocks,
 			 *  need to account for leaf block credit
 			 *
 			 *  bitmaps and block group descriptor blocks
-			 *  and other metadat blocks still need to be
+			 *  and other metadata blocks still need to be
 			 *  accounted.
 			 */
 			/* 1 bitmap, 1 block group descriptor */

fs/ext4/inode.c

@@ -458,7 +458,7 @@ static void set_buffers_da_mapped(struct inode *inode,
  * the buffer head is mapped.
  *
  * It returns 0 if plain look up failed (blocks have not been allocated), in
- * that casem, buffer head is unmapped
+ * that case, buffer head is unmapped
  *
  * It returns the error in case of allocation failure.
  */
@@ -497,7 +497,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 	 * Returns if the blocks have already allocated
 	 *
 	 * Note that if blocks have been preallocated
-	 * ext4_ext_get_block() returns th create = 0
+	 * ext4_ext_get_block() returns the create = 0
 	 * with buffer head unmapped.
 	 */
 	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)