The quilt patch titled Subject: mm/rmap: fix misplaced parenthesis of a likely() has been removed from the -mm tree. Its filename was mm-rmap-fix-misplaced-parenthesis-of-a-likely.patch
This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Steven Rostedt rostedt@goodmis.org Subject: mm/rmap: fix misplaced parenthesis of a likely() Date: Fri, 1 Dec 2023 14:59:36 -0500
From: Steven Rostedt (Google) rostedt@goodmis.org
Running my yearly branch profiler to see where likely/unlikely annotation may be added or removed, I discovered this:
correct incorrect % Function File Line ------- --------- - -------- ---- ---- 0 457918 100 page_try_dup_anon_rmap rmap.h 264 [..] 458021 0 0 page_try_dup_anon_rmap rmap.h 265
I thought it was interesting that line 264 of rmap.h had a 100% incorrect annotation, but the line directly below it was 100% correct. Looking at the code:
if (likely(!is_device_private_page(page) && unlikely(page_needs_cow_for_dma(vma, page))))
It didn't make sense. The "likely()" was around the entire if statement (not just the "!is_device_private_page(page)"), which also included the "unlikely()" portion of that if condition.
If the unlikely portion is unlikely to be true, that would make the entire if condition unlikely to be true, so it made no sense at all to say the entire if condition is true.
What is more likely to be likely is just the first part of the if statement before the && operation. It's likely to be a misplaced parenthesis. And after making the if condition broken into a likely() && unlikely(), both now appear to be correct!
Link: https://lkml.kernel.org/r/20231201145936.5ddfdb50@gandalf.local.home Fixes:fb3d824d1a46c ("mm/rmap: split page_dup_rmap() into page_dup_file_rmap() and page_try_dup_anon_rmap()") Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Acked-by: Vlastimil Babka vbabka@suse.cz Cc: David Hildenbrand david@redhat.com Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/rmap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/include/linux/rmap.h~mm-rmap-fix-misplaced-parenthesis-of-a-likely +++ a/include/linux/rmap.h @@ -261,8 +261,8 @@ static inline int page_try_dup_anon_rmap * guarantee the pinned page won't be randomly replaced in the * future on write faults. */ - if (likely(!is_device_private_page(page) && - unlikely(page_needs_cow_for_dma(vma, page)))) + if (likely(!is_device_private_page(page)) && + unlikely(page_needs_cow_for_dma(vma, page))) return -EBUSY;
ClearPageAnonExclusive(page); _
Patches currently in -mm which might be from rostedt@goodmis.org are