[PATCH v2] mm: gup: fix comment of __get_user_pages()

[Liu Xiang <liuxiang_1999@126.com>]

Fix comment of __get_user_pages() and make it more clear.

Suggested-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Liu Xiang <liuxiang_1999@126.com>
---

Changes in v2:
 as suggested by John, rewrite the comment about return value.

 mm/gup.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 8f236a3..bc6a254 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -734,11 +734,17 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
  *		Or NULL if the caller does not require them.
  * @nonblocking: whether waiting for disk IO or mmap_sem contention
  *
- * Returns number of pages pinned. This may be fewer than the number
- * requested. If nr_pages is 0 or negative, returns 0. If no pages
- * were pinned, returns -errno. Each page returned must be released
- * with a put_page() call when it is finished with. vmas will only
- * remain valid while mmap_sem is held.
+ * Returns either number of pages pinned (which may be less than the
+ * number requested), or an error. Details about the return value:
+ *
+ * -- If nr_pages is 0, returns 0.
+ * -- If nr_pages is >0, but no pages were pinned, returns -errno.
+ * -- If nr_pages is >0, and some pages were pinned, returns the number of
+ *    pages pinned. Again, this may be less than nr_pages.
+ *
+ * The caller is responsible for releasing returned @pages, via put_page().
+ *
+ * @vmas are valid only as long as mmap_sem is held.
  *
  * Must be called with mmap_sem held.  It may be released.  See below.
  *
-- 
1.9.1