Re: [PATCH 1/2] fs: introduce sendfd() syscall

From: Al Viro <viro@ZenIV.linux.org.uk>
To: Alex Dubov <alex.dubov@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Alex Dubov <oakad@yahoo.com>
Subject: Re: [PATCH 1/2] fs: introduce sendfd() syscall
Date: Wed, 3 Dec 2014 03:40:20 +0000	[thread overview]
Message-ID: <20141203034020.GI29748@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAPs88r8m2QmaOWy623swGk=T3cyG85X3N7Z9tAp3nZvD0Tch+A@mail.gmail.com>

On Wed, Dec 03, 2014 at 01:22:33PM +1100, Alex Dubov wrote:

> On a less related note, I hope you will agree that the simpler
> mechanism for this very in-demand feature is long overdue on Linux
> (every man and his dog are passing fds around these days).

... and I'm less than sure that it's a good thing.  If nothing else,
once the pieces of your program are passing descriptors around freely,
you have created a barfball that will be impossible to split between
several boxen if you run into scalability issues.  Descriptor-passing
is limited to a single system; you *can't* do that between e.g. components
of a cluster.  So it's not an unmixed blessing, just as overuse of
shared memory segments, etc.  They do have their uses, but that needs
to be carefully considered every time, or you'll create a major headache
a few years down the road.