mm/gup: make get_user_pages_fast_only() return the common return value

There are only two callers, both can handle the common return code:

- get_user_page_fast_only() checks == 1

- gfn_to_page_many_atomic() already returns -1, and the only caller
  checks for negative return values

Remove the restriction against returning negative values.

Link: https://lkml.kernel.org/r/11-v2-987e91b59705+36b-gup_tidy_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 91c8ab5..91d0470 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3005,8 +3005,6 @@ static int internal_get_user_pages_fast(unsigned long start,
  *
  * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to
  * the regular GUP.
- * Note a difference with get_user_pages_fast: this always returns the
- * number of pages pinned, 0 if no pages were pinned.
  *
  * If the architecture does not support this function, simply return with no
  * pages pinned.
@@ -3018,7 +3016,6 @@ static int internal_get_user_pages_fast(unsigned long start,
 int get_user_pages_fast_only(unsigned long start, int nr_pages,
                             unsigned int gup_flags, struct page **pages)
 {
-       int nr_pinned;
        /*
         * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
         * because gup fast is always a "pin with a +1 page refcount" request.
@@ -3030,19 +3027,7 @@ int get_user_pages_fast_only(unsigned long start, int nr_pages,
                               FOLL_GET | FOLL_FAST_ONLY))
                return -EINVAL;
 
-       nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
-                                                pages);
-
-       /*
-        * As specified in the API description above, this routine is not
-        * allowed to return negative values. However, the common core
-        * routine internal_get_user_pages_fast() *can* return -errno.
-        * Therefore, correct for that here:
-        */
-       if (nr_pinned < 0)
-               nr_pinned = 0;
-
-       return nr_pinned;
+       return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast_only);