From d081107867b85cc7454b9d4f5aea47f65bcf06d1 Mon Sep 17 00:00:00 2001 From: Michael S. Tsirkin Date: Fri, 13 Apr 2018 15:35:23 -0700 Subject: mm/gup.c: document return value __get_user_pages_fast handles errors differently from get_user_pages_fast: the former always returns the number of pages pinned, the later might return a negative error code. Link: http://lkml.kernel.org/r/1522962072-182137-6-git-send-email-mst@redhat.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Andrew Morton Cc: Kirill A. Shutemov Cc: Huang Ying Cc: Jonathan Corbet Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Thorsten Leemhuis Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/gup.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'mm/gup.c') diff --git a/mm/gup.c b/mm/gup.c index db5346f80a5a..76af4cfeaf68 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1740,7 +1740,9 @@ bool gup_fast_permitted(unsigned long start, int nr_pages, int write) /* * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to - * the regular GUP. It will only return non-negative values. + * 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. */ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) -- cgit v1.2.3-55-g7522