linux-kernel - [PATCH 4/4 v2] mm: use access_remote_vm() in get

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Date:   Tue, 27 Feb 2018 08:25:51 +0800
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     akpm@...ux-foundation.org, mingo@...nel.org, adobriyan@...il.com
Cc:     yang.shi@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/4 v2] mm: use access_remote_vm() in get_cmdline()

get_cmdline() is using access_process_vm() which increases mm reference
count, but the mm reference count has been increased before calling
access_process_vm() and it is kept across get_cmdline(). It sounds
unnecessary to get mm reference count increased twice, so replace
access_process_vm() to access_remote_vm() which requires caller increase
mm reference count.

Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
---
 mm/util.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index c125050..9b40637 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -732,7 +732,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 	if (len > buflen)
 		len = buflen;
 
-	res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
+	res = access_remote_vm(mm, arg_start, buffer, len, FOLL_FORCE);
 
 	/*
 	 * If the nul at the end of args has been overwritten, then
@@ -746,7 +746,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 			len = env_end - env_start;
 			if (len > buflen - res)
 				len = buflen - res;
-			res += access_process_vm(task, env_start,
+			res += access_remote_vm(mm, env_start,
 						 buffer+res, len,
 						 FOLL_FORCE);
 			res = strnlen(buffer, res);
-- 
1.8.3.1