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authorMichael S. Tsirkin <mst@redhat.com>2018-04-13 15:35:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-13 17:10:27 -0700
commitd081107867b85cc7454b9d4f5aea47f65bcf06d1 (patch)
tree4cd38640b68f5b53262a2a1e354e3c6efc131103 /mm
parentc61611f70958d86f659bca25c02ae69413747a8d (diff)
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 <mst@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Thorsten Leemhuis <regressions@leemhuis.info> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c4
-rw-r--r--mm/util.c6
2 files changed, 7 insertions, 3 deletions
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)
diff --git a/mm/util.c b/mm/util.c
index 1fc4fa7576f7..45fc3169e7b0 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -297,8 +297,10 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
/*
* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
* back to the regular GUP.
- * If the architecture not support this function, simply return with no
- * page pinned
+ * 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.
*/
int __weak __get_user_pages_fast(unsigned long start,
int nr_pages, int write, struct page **pages)