netdev - Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3)

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Message-ID: <1446073709.7476.93.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 28 Oct 2015 16:08:29 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	David Miller <davem@...emloft.net>, stephen@...workplumber.org,
	netdev@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	dhowells@...hat.com, linux-fsdevel@...r.kernel.org
Subject: Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect
 for sockets in accept(3)

On Wed, 2015-10-28 at 22:33 +0000, Al Viro wrote:
> On Wed, Oct 28, 2015 at 02:44:28PM -0700, Eric Dumazet wrote:
> 
> > Well, all this complexity goes away with a O_FD_FASTALLOC /
> > SOCK_FD_FASTALLOC bit in various fd allocations, which specifically
> > tells the kernel we do not care getting the lowest possible fd as POSIX
> > mandates.
> 
> ... which won't do a damn thing for existing userland.

For the userland that need +5,000,000 socket, I can tell you they are
using this flag as soon they are aware it exists ;)

> 
> > Except for legacy stuff and stdin/stdout/stderr games, I really doubt
> > lot of applications absolutely rely on the POSIX thing...
> 
> We obviously can't turn that into default behaviour, though.  BTW, what
> distribution do you have in mind for those random descriptors?  Uniform
> on [0,INT_MAX] is a bad idea for obvious reasons - you'll blow the
> memory footprint pretty soon...

Simply [0 , fdt->max_fds] is working well in most cases.



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