linux-kernel - [PATCH v3] mm: gup: fix comments of __get_user_pages() and get_user_pages

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Message-Id: <1572443533-3118-1-git-send-email-liuxiang_1999@126.com>
Date:   Wed, 30 Oct 2019 21:52:13 +0800
From:   Liu Xiang <liuxiang_1999@....com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, jhubbard@...dia.com,
        liuxiang_1999@....com
Subject: [PATCH v3] mm: gup: fix comments of __get_user_pages() and get_user_pages_remote()

Fix comments of __get_user_pages() and get_user_pages_remote(),
make them more clear.

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

---

Changes in v3:
 as suggested by John, apply the same fix to get_user_pages_remote().
---
 mm/gup.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 8f236a3..c36c621 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.
  *
@@ -1107,11 +1113,17 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
  *		subsequently whether VM_FAULT_RETRY functionality can be
  *		utilised. Lock must initially be held.
  *
- * 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 for read or write.
  *
-- 
1.9.1