The patch titled
Subject: mm: avoid unnecessary page table walk for __get_user_pages
has been added to the -mm mm-unstable branch. Its filename is
mm-avoid-unnecessary-page-table-walk-for-__get_user_pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-avoid-unnecessary-page-table-walk-for-__get_user_pages.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Chen Wandun <chenwandun@xxxxxxxxxx>
Subject: mm: avoid unnecessary page table walk for __get_user_pages
Date: Tue, 6 Sep 2022 10:44:01 +0800
There is no need to walk page tables and find pages if faultin_page)_
succeeds and __get_user_pages)_ doesn't care about populating the pages[]
array. So directly go on to handle the next page.
Link: https://lkml.kernel.org/r/20220906024401.133336-1-chenwandun@xxxxxxxxxx
Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/gup.c~mm-avoid-unnecessary-page-table-walk-for-__get_user_pages
+++ a/mm/gup.c
@@ -1175,7 +1175,10 @@ retry:
PTR_ERR(page) == -EMLINK, locked);
switch (ret) {
case 0:
- goto retry;
+ if (pages)
+ goto retry;
+ else
+ goto next_page;
case -EBUSY:
case -EAGAIN:
ret = 0;
_
Patches currently in -mm which might be from chenwandun@xxxxxxxxxx are
mm-avoid-unnecessary-page-table-walk-for-__get_user_pages.patch
