mm/swap: fix the comment of get_kernel_pages

If no pages were pinned, 0 is returned in fact.  Fix the corresponding
comment.

[akpm@linux-foundation.org: s/nr_pages/nr_segs/ also, per David, reflow comment]
Link: https://lkml.kernel.org/r/20220509131416.17553-15-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swap.c

@@ -166,10 +166,10 @@ EXPORT_SYMBOL(put_pages_list);
  * @pages:	array that receives pointers to the pages pinned.
  *		Should be at least nr_segs long.
  *
- * 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.
+ * Returns number of pages pinned. This may be fewer than the number requested.
+ * If nr_segs is 0 or negative, returns 0.  If no pages were pinned, returns 0.
+ * Each page returned must be released with a put_page() call when it is
+ * finished with.
  */
 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
 		struct page **pages)