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Date: Fri, 13 Feb 2004 02:01:13 +0000
From: Jamie Lokier <jamie@shareable.org>
To: Tim Hockin <thockin@sun.com>
Cc: Jim Houston <jim.houston@ccur.com>, Andrew Morton <akpm@osdl.org>,
       torvalds@osdl.org, viro@parcelfarce.linux.theplanet.co.uk,
       linux-kernel@vger.kernel.org, george@mvista.com
Subject: Re: PATCH - raise max_anon limit
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References: <20040211222849.GL9155@sun.com> <20040211144844.0e4a2888.akpm@osdl.org> <20040211233852.GN9155@sun.com> <20040211155754.5068332c.akpm@osdl.org> <20040212003840.GO9155@sun.com> <20040211164233.5f233595.akpm@osdl.org> <20040212010822.GP9155@sun.com> <20040211172046.37e18a2f.akpm@osdl.org> <1076606773.990.165.camel@new.localdomain> <20040212184903.GS9155@sun.com>
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Tim Hockin wrote:
> > The rational for avoiding immediate reuse of id values is to catch
> > application errors.   Consider:
> > 
> > 	fd1 = open_like_call(...);
> > 	read(fd1,...);
> > 	close(fd1);
> > 	fd2 = open_like_call(...);
> > 	write(fd1...);
> > 
> > If fd2 has a different value than the recently closed fd1, the
> > error is detected immediately.
> 
> Is that really worth working around in such a gross way?  No offense to the
> idea, but that's a pretty dumb bug to be hacking a failsafe for :)

I'm pretty sure POSIX requires fd2 to be equal to fd1 if it is the
lowest free file descriptor number.

Unfortunately.  An O(1) fd allocation algorithm would be nice.

-- Jamie