mm: rewrite the comment over migrate_pages() more comprehensibly

The comment over migrate_pages() looks quite weird, and makes it hard to
grasp what it is trying to say.  Rewrite it more comprehensibly.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/migrate.c

@@ -973,19 +973,23 @@ out:
 }
 
 /*
- * migrate_pages
+ * migrate_pages - migrate the pages specified in a list, to the free pages
+ *		   supplied as the target for the page migration
  *
- * The function takes one list of pages to migrate and a function
- * that determines from the page to be migrated and the private data
- * the target of the move and allocates the page.
+ * @from:		The list of pages to be migrated.
+ * @get_new_page:	The function used to allocate free pages to be used
+ *			as the target of the page migration.
+ * @private:		Private data to be passed on to get_new_page()
+ * @mode:		The migration mode that specifies the constraints for
+ *			page migration, if any.
+ * @reason:		The reason for page migration.
  *
- * The function returns after 10 attempts or if no pages
- * are movable anymore because to has become empty
- * or no retryable pages exist anymore.
- * Caller should call putback_lru_pages to return pages to the LRU
+ * The function returns after 10 attempts or if no pages are movable any more
+ * because the list has become empty or no retryable pages exist any more.
+ * The caller should call putback_lru_pages() to return pages to the LRU
  * or free list only if ret != 0.
  *
- * Return: Number of pages not migrated or error code.
+ * Returns the number of pages that were not migrated, or an error code.
  */
 int migrate_pages(struct list_head *from, new_page_t get_new_page,
 		unsigned long private, enum migrate_mode mode, int reason)