From 90f31d0ea88880f780574f3d0bb1a227c4c66ca3 Mon Sep 17 00:00:00 2001
From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Date: Thu, 16 Apr 2015 12:47:56 -0700
Subject: mm: rcu-protected get_mm_exe_file()

This patch removes mm->mmap_sem from mm->exe_file read side.
Also it kills dup_mm_exe_file() and moves exe_file duplication into
dup_mmap() where both mmap_sems are locked.

[akpm@linux-foundation.org: fix comment typo]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 fs/file.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

(limited to 'fs/file.c')

diff --git a/fs/file.c b/fs/file.c
index ee738ea028fa..93c5f89c248b 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -638,8 +638,7 @@ static struct file *__fget(unsigned int fd, fmode_t mask)
 	file = fcheck_files(files, fd);
 	if (file) {
 		/* File object ref couldn't be taken */
-		if ((file->f_mode & mask) ||
-		    !atomic_long_inc_not_zero(&file->f_count))
+		if ((file->f_mode & mask) || !get_file_rcu(file))
 			file = NULL;
 	}
 	rcu_read_unlock();
-- 
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