linux-kernel - Re: [PATCH AUTOSEL 4.9 20/87] fs: Make splice() and tee() take into account O

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Message-ID: <20190328120417.36bae781@gandalf.local.home>
Date:   Thu, 28 Mar 2019 12:04:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Slavomir Kaslev <kaslevs@...are.com>
Cc:     "sashal@...nel.org" <sashal@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 4.9 20/87] fs: Make splice() and tee() take into
 account O_NONBLOCK flag on pipes

On Thu, 28 Mar 2019 15:37:49 +0000
Slavomir Kaslev <kaslevs@...are.com> wrote:

> On Wed, 2019-03-27 at 14:19 -0400, Sasha Levin wrote:
> > From: Slavomir Kaslev <kaslevs@...are.com>
> > 
> > [ Upstream commit ee5e001196d1345b8fee25925ff5f1d67936081e ]
> > 
> > The current implementation of splice() and tee() ignores O_NONBLOCK
> > set
> > on pipe file descriptors and checks only the SPLICE_F_NONBLOCK flag
> > for
> > blocking on pipe arguments.  This is inconsistent since splice()-ing
> > from/to non-pipe file descriptors does take O_NONBLOCK into
> > consideration.
> > 
> > Fix this by promoting O_NONBLOCK, when set on a pipe, to
> > SPLICE_F_NONBLOCK.  
> 
> Hey Sasha,
> 
> I don't think that this patch should be merged to stable kernels. It's
> more of a feature rather than a bug/regression fix and it changes how
> splice() has been working from day one.
> 
> Can you please drop it from the stable queues?
> 

On the other hand, it keeps stable more in sync with what mainline has.
If someone writes new code against a stable release, and depends on
this behavior, it's less likely to break when they run it on a newer
kernel. Which means its less likely that Linus will revert your
change ;-)

-- Steve