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From: Yang Shi <yang.shi@linux.alibaba.com>
To: akpm@linux-foundation.org, mingo@kernel.org, adobriyan@gmail.com
Cc: yang.shi@linux.alibaba.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 4/4 v2] mm: use access_remote_vm() in get_cmdline()
Date: Tue, 27 Feb 2018 08:25:51 +0800	[thread overview]
Message-ID: <1519691151-101999-5-git-send-email-yang.shi@linux.alibaba.com> (raw)
In-Reply-To: <1519691151-101999-1-git-send-email-yang.shi@linux.alibaba.com>

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@linux.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

  parent reply	other threads:[~2018-02-27  0:26 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-27  0:25 [RFC PATCH 0/4 v2] Define killable version for access_remote_vm() and use it in fs/proc Yang Shi
2018-02-27  0:25 ` [PATCH 1/4 v2] mm: add access_remote_vm_killable APIs Yang Shi
2018-02-27  0:25 ` [PATCH 2/4 v2] fs: proc: use down_read_killable in proc_pid_cmdline_read() Yang Shi
2018-02-27  0:25 ` [PATCH 3/4 v2] fs: proc: use down_read_killable() in environ_read() Yang Shi
2018-02-27  7:15   ` Alexey Dobriyan
2018-02-27 16:59     ` Yang Shi
2018-02-27  0:25 ` Yang Shi [this message]
2018-02-27  1:02 ` [RFC PATCH 0/4 v2] Define killable version for access_remote_vm() and use it in fs/proc David Rientjes
2018-02-27  1:25   ` Yang Shi
2018-02-27  1:47     ` David Rientjes
2018-03-01  0:17       ` Yang Shi
2018-03-06 18:45 ` Yang Shi
2018-03-06 20:45 ` Andrew Morton
2018-03-06 21:17   ` Yang Shi
2018-03-06 21:41     ` Andrew Morton
2018-03-07  0:47       ` Yang Shi

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