linux-kernel - Re: [RFC][PATCH] VFS: create /proc/<pid>/mountinfo

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Message-ID: <47978F5D.8010006@zytor.com>
Date:	Wed, 23 Jan 2008 11:02:53 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@....cz>
CC:	Miklos Szeredi <miklos@...redi.hu>, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	util-linux-ng@...r.kernel.org, linuxram@...ibm.com,
	viro@....linux.org.uk, hch@...radead.org, a.p.zijlstra@...llo.nl
Subject: Re: [RFC][PATCH] VFS: create /proc/<pid>/mountinfo

Pavel Machek wrote:
> On Sun 2008-01-20 09:23:00, Miklos Szeredi wrote:
>>> Miklos Szeredi wrote:
>>>> - for mount ID's use IDA (from the IDR library) instead of a 32bit
>>>>   counter, which could overflow
>>> IDAs tend to get reused quickly, which can cause race conditions.  Any 
>>> reason not to just use a 64-bit counter?
>> They tend to become hard to parse/compare for humans after a while.
>> And all this is basically only for humans, so race conditions don't
>> really matter.  Also a changed mount with a reused ID is easily
>> identified by comparing the other fields.
> 
> Hmm, smart humans only compare last few digits if they don't care
> about 100% reliability, and dumb software compares 64bits easily...
> 							Pavel

Indeed.

And this is most certainly NOT only for humans, and race conditions most 
certainly matter.

	-hpa
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