From: Steven Whitehouse <swhiteho-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Richard Hansen <rhansen-A08e6c8yq/Q@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Greg Troxel <gdt-2FjktZCtrC/QT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC
Date: Wed, 02 Apr 2014 12:45:19 +0100 [thread overview]
Message-ID: <1396439119.2726.29.camel@menhir> (raw)
In-Reply-To: <20140402111032.GA27551-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Hi,
On Wed, 2014-04-02 at 04:10 -0700, Christoph Hellwig wrote:
> On Tue, Apr 01, 2014 at 02:25:45PM -0400, Richard Hansen wrote:
> > For the flags parameter, POSIX says "Either MS_ASYNC or MS_SYNC shall
> > be specified, but not both." [1] There was already a test for the
> > "both" condition. Add a test to ensure that the caller specified one
> > of the flags; fail with EINVAL if neither are specified.
>
> This breaks various (sloppy) existing userspace for no gain.
>
> NAK.
>
Agreed. It might be better to have something like:
if (flags == 0)
flags = MS_SYNC;
That way applications which don't set the flags (and possibly also don't
check the return value, so will not notice an error return) will get the
sync they desire. Not that either of those things is desirable, but at
least we can make the best of the situation. Probably better to be slow
than to potentially lose someone's data in this case,
Steve.
WARNING: multiple messages have this Message-ID (diff)
From: Steven Whitehouse <swhiteho@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Richard Hansen <rhansen@bbn.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, Greg Troxel <gdt@ir.bbn.com>
Subject: Re: [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC
Date: Wed, 02 Apr 2014 12:45:19 +0100 [thread overview]
Message-ID: <1396439119.2726.29.camel@menhir> (raw)
In-Reply-To: <20140402111032.GA27551@infradead.org>
Hi,
On Wed, 2014-04-02 at 04:10 -0700, Christoph Hellwig wrote:
> On Tue, Apr 01, 2014 at 02:25:45PM -0400, Richard Hansen wrote:
> > For the flags parameter, POSIX says "Either MS_ASYNC or MS_SYNC shall
> > be specified, but not both." [1] There was already a test for the
> > "both" condition. Add a test to ensure that the caller specified one
> > of the flags; fail with EINVAL if neither are specified.
>
> This breaks various (sloppy) existing userspace for no gain.
>
> NAK.
>
Agreed. It might be better to have something like:
if (flags == 0)
flags = MS_SYNC;
That way applications which don't set the flags (and possibly also don't
check the return value, so will not notice an error return) will get the
sync they desire. Not that either of those things is desirable, but at
least we can make the best of the situation. Probably better to be slow
than to potentially lose someone's data in this case,
Steve.
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WARNING: multiple messages have this Message-ID (diff)
From: Steven Whitehouse <swhiteho@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Richard Hansen <rhansen@bbn.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, Greg Troxel <gdt@ir.bbn.com>
Subject: Re: [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC
Date: Wed, 02 Apr 2014 12:45:19 +0100 [thread overview]
Message-ID: <1396439119.2726.29.camel@menhir> (raw)
In-Reply-To: <20140402111032.GA27551@infradead.org>
Hi,
On Wed, 2014-04-02 at 04:10 -0700, Christoph Hellwig wrote:
> On Tue, Apr 01, 2014 at 02:25:45PM -0400, Richard Hansen wrote:
> > For the flags parameter, POSIX says "Either MS_ASYNC or MS_SYNC shall
> > be specified, but not both." [1] There was already a test for the
> > "both" condition. Add a test to ensure that the caller specified one
> > of the flags; fail with EINVAL if neither are specified.
>
> This breaks various (sloppy) existing userspace for no gain.
>
> NAK.
>
Agreed. It might be better to have something like:
if (flags == 0)
flags = MS_SYNC;
That way applications which don't set the flags (and possibly also don't
check the return value, so will not notice an error return) will get the
sync they desire. Not that either of those things is desirable, but at
least we can make the best of the situation. Probably better to be slow
than to potentially lose someone's data in this case,
Steve.
next prev parent reply other threads:[~2014-04-02 11:45 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-01 18:25 [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC Richard Hansen
2014-04-01 18:25 ` Richard Hansen
[not found] ` <533B04A9.6090405-A08e6c8yq/Q@public.gmane.org>
2014-04-01 19:32 ` Michael Kerrisk (man-pages)
2014-04-01 19:32 ` Michael Kerrisk (man-pages)
2014-04-01 19:32 ` Michael Kerrisk (man-pages)
2014-04-02 0:53 ` Richard Hansen
2014-04-02 0:53 ` Richard Hansen
[not found] ` <533B1439.3010403-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-04-02 10:45 ` chrubis-AlSwsSmVLrQ
2014-04-02 10:45 ` chrubis
2014-04-02 10:45 ` chrubis
2014-04-02 11:10 ` Christoph Hellwig
2014-04-02 11:10 ` Christoph Hellwig
2014-04-02 11:10 ` Christoph Hellwig
[not found] ` <20140402111032.GA27551-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2014-04-02 11:45 ` Steven Whitehouse [this message]
2014-04-02 11:45 ` Steven Whitehouse
2014-04-02 11:45 ` Steven Whitehouse
2014-04-02 23:44 ` Richard Hansen
2014-04-02 23:44 ` Richard Hansen
2014-04-02 23:44 ` Richard Hansen
2014-04-03 8:25 ` Michael Kerrisk (man-pages)
2014-04-03 8:25 ` Michael Kerrisk (man-pages)
2014-04-03 11:51 ` Christopher Covington
2014-04-03 11:51 ` Christopher Covington
2014-04-04 6:54 ` Michael Kerrisk (man-pages)
2014-04-04 6:54 ` Michael Kerrisk (man-pages)
2014-04-04 6:54 ` Michael Kerrisk (man-pages)
2014-04-03 12:57 ` Greg Troxel
2014-04-03 12:57 ` Greg Troxel
2014-04-04 7:11 ` Michael Kerrisk (man-pages)
2014-04-04 7:11 ` Michael Kerrisk (man-pages)
2014-04-04 7:11 ` Michael Kerrisk (man-pages)
2014-04-03 20:23 ` Richard Hansen
2014-04-03 20:23 ` Richard Hansen
2014-04-04 6:53 ` Christoph Hellwig
2014-04-04 6:53 ` Christoph Hellwig
2014-04-04 7:12 ` [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC [resend] Michael Kerrisk (man-pages)
2014-04-04 7:12 ` Michael Kerrisk (man-pages)
2014-04-04 7:12 ` Michael Kerrisk (man-pages)
2014-04-04 14:07 ` Peter Zijlstra
2014-04-04 14:07 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2013-09-01 19:58 [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC Richard Hansen
2013-09-01 19:58 ` Richard Hansen
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