Re: [PATCH v3] mm: gup: fix comments of __get_user_pages() and get_user_pages_remote()

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On 30.10.19 14:52, Liu Xiang wrote:
Fix comments of __get_user_pages() and get_user_pages_remote(),
make them more clear.

Suggested-by: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Liu Xiang <liuxiang_1999@xxxxxxx>

---

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.
   *


Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

--

Thanks,

David / dhildenb






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