linux-kernel - Re: sparc: Clashing values for O_PATH and FMODE

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Message-ID: <CAHse=S-f5o3vbT+b1D5baEWCWMUnDyLSxM88+vwwymFuLrTirg@mail.gmail.com>
Date:	Thu, 20 Nov 2014 12:12:23 +0000
From:	David Drysdale <drysdale@...gle.com>
To:	David Miller <davem@...emloft.net>, Eric Paris <eparis@...hat.com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	sparclinux@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: sparc: Clashing values for O_PATH and FMODE_NONOTIFY?

[+linux-fsdevel, without the typo this time]

On Wed, Nov 19, 2014 at 8:30 PM, David Miller <davem@...emloft.net> wrote:
> From: David Drysdale <drysdale@...gle.com>
> Date: Tue, 18 Nov 2014 13:13:51 +0000
>
>> Hi folks,
>>
>> It looks like the value for O_PATH on sparc:
>>
>>   arch/sparc/include/uapi/asm/fcntl.h:37:#define O_PATH 0x1000000
>>
>> clashes with the arch-independent value for __FMODE_NONOTIFY:
>>
>>   include/linux/fs.h:137:#define FMODE_NONOTIFY ((__force fmode_t)0x1000000)
>>   include/linux/fs.h:2764:#define __FMODE_NONOTIFY ((__force int)
>> FMODE_NONOTIFY)
>>
>> and they are both in the same numbering space, as indicated by the
>> comment at the top of include/uapi/asm-generic/fcntl.h and the use in
>> fs/notify/fanotify/fanotify_user.c:715.
>>
>> Presumably this could theoretically cause problems (no notifications for
>> O_PATH files on SPARC?), so would it be a good idea to renumber
>> FMODE_NONOTIFY?  (I *think* that value is entirely kernel-internal.)
>>
>> Given that this has happened before (12ed2e36c98aec6c4155 "fanotify:
>> FMODE_NONOTIFY and __O_SYNC in sparc conflict") it would probably
>> also be a good idea to add __FMODE_NOTIFY to the uniqueness check in
>> fs/fcntl.c:fcntl_init().
>>
>> Thoughts?
>
> I think you will need to change the internal value, to not clash with
> the sparc exported one, for sure.

Well, I was sort of hoping someone else might volunteer to make the
change :-) --  I don't use fanotify (or sparc for that matter), I just
happened to notice the clash in passing.

But I'm happy to have a go, although I can't test much.  It would be
good to hear from the fanotify maintainers first, though -- Eric?

Thanks,
David
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