linux-kernel - [PATCH 5/5] fs/proc/task_mmu.c: change m_start() to rely on priv->mm and avoid mm

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Message-ID: <20140803212047.GF13330@redhat.com>
Date:	Sun, 3 Aug 2014 23:20:47 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Howells <dhowells@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sasha Levin <levinsasha928@...il.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"David S. Miller" <davem@...emloft.net>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 5/5] fs/proc/task_mmu.c: change m_start() to rely on
	priv->mm and avoid mm_access()

Finally we can change m_start() to avoid mm_access(), it can simply do
atomic_inc_not_zero(mm_users).

I'll try to verify, if this is the only change we need, then this one
line change doesn't deserve a separate patch.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/proc/task_mmu.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 1cc623d..7ec8eb5 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -165,9 +165,9 @@ static void *m_start(struct seq_file *m, loff_t *pos)
 	if (!priv->task)
 		return ERR_PTR(-ESRCH);
 
-	mm = mm_access(priv->task, PTRACE_MODE_READ);
-	if (!mm || IS_ERR(mm))
-		return mm;
+	mm = priv->mm;
+	if (!mm || !atomic_inc_not_zero(&mm->mm_users))
+		return NULL;
 	down_read(&mm->mmap_sem);
 
 	tail_vma = get_gate_vma(mm);
-- 
1.5.5.1


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