From 38fc1011af6bcd45032d4e0e3924c49b3c5d1adf Mon Sep 17 00:00:00 2001
From: zhangkui <zhangkui@oppo.com>
Date: Thu, 2 Sep 2021 15:01:11 -0700
Subject: [PATCH] mm/madvise: add MADV_WILLNEED to process_madvise()

References: bsc#1190208 (MM functional and performance backports)
Patch-mainline: v5.15-rc1
Git-commit: d5fffc5aff269717a035baa087630adca612a6c4

There is a usecase in Android that an app process's memory is swapped out
by process_madvise() with MADV_PAGEOUT, such as the memory is swapped to
zram or a backing device.  When the process is scheduled to running, like
switch to foreground, multiple page faults may cause the app dropped
frames.

To reduce the problem, System Management Software can read-ahead memory
of the process immediately when the app switches to forground.  Calling
process_madvise() with MADV_WILLNEED can meet this need.

Link: https://lkml.kernel.org/r/20210804082010.12482-1-zhangkui@oppo.com
Signed-off-by: zhangkui <zhangkui@oppo.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 mm/madvise.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/madvise.c b/mm/madvise.c
index 5c065bc8b5f6..4a15a83031f6 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1048,6 +1048,7 @@ process_madvise_behavior_valid(int behavior)
 	switch (behavior) {
 	case MADV_COLD:
 	case MADV_PAGEOUT:
+	case MADV_WILLNEED:
 		return true;
 	default:
 		return false;