linux-ext4 - [PATCH] vfs: add missing check for __O_TMPFILE in fcntl

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Date:	Thu, 25 Jul 2013 08:13:19 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	jon ernst <jonernst07@...il.com>
Cc:	linux-ext4@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH] vfs: add missing check for __O_TMPFILE in fcntl_init() (Re:
 [PATCH] ext4: fix...)

On Wed, Jul 24, 2013 at 09:58:45PM +0000, jon ernst wrote:
> > My purpose is to trigger this bug and fix it.  So I manually define this
> > flag for my convenience.
> >
> >> I saw it has
> >> been defined in header file. (fcntl.h) Did I miss anything?
> >
> > I guess that you might 'include <fcntl.h>' header file, right?  But the
> > O_TMPFILE is defined in $LINUX/include/uapi/asm-generic/fcntl.h.  So
> > maybe compiler couldn't find this header file.
> >
> > Regards,
> >                                                 - Zheng
> --
> Got it. Thank you.  BTW, the weird thing is I didn't see any
> discussion on ext4 mailing list before Al Viro committed this change.
> The first time I heard about this is someone reporting a bug about it.
> Document about this FLAG might be necessary.

Oh, this flag has been discussed in linux-fsdevel mailing list [1].
Maybe you don't subscribe it.

1. https://lkml.org/lkml/2013/7/3/181

> Also, about this code:
> 
> /* a horrid kludge trying to make sure that this will fail on old kernels */
> #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
> 
> why not doing something like this:
> 
> #ifndef O_TMPFILE
> /* a horrid kludge trying to make sure that this will fail on old kernels */
> #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
> #endif

Sorry, I don't take a closer look at that thread.  I look at the code,
and it seems that there is no any rule about adding '#ifndef XXX'.
Meanwhile, I notice a comment:

/*
 * When introducing new O_* bits, please check its uniqueness in fcntl_init().
 */

But we are missing adding O_TMPFILE flag in fcntl_init().  So I attach a
patch below.

Al, could you please answer this question?  Thanks.

Regards,
                                                - Zheng

Subject: [PATCH] vfs: add missing check for __O_TMPFILE in fcntl_init()

From: Zheng Liu <wenqing.lz@...bao.com>

As comment in include/uapi/asm-generic/fcntl.h described, when
introducing new O_* bits, we need to check its uniqueness in
fcntl_init().  But __O_TMPFILE bit is missing.  So fix it.

Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
---
*This patch is against ext4/dev tree.*

 fs/fcntl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 6599222..65343c3 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -730,14 +730,14 @@ static int __init fcntl_init(void)
 	 * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
 	 * is defined as O_NONBLOCK on some platforms and not on others.
 	 */
-	BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+	BUILD_BUG_ON(20 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
 		O_RDONLY	| O_WRONLY	| O_RDWR	|
 		O_CREAT		| O_EXCL	| O_NOCTTY	|
 		O_TRUNC		| O_APPEND	| /* O_NONBLOCK	| */
 		__O_SYNC	| O_DSYNC	| FASYNC	|
 		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
 		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
-		__FMODE_EXEC	| O_PATH
+		__FMODE_EXEC	| O_PATH	| __O_TMPFILE
 		));
 
 	fasync_cache = kmem_cache_create("fasync_cache",
-- 
1.7.9.7

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