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Date: Wed, 23 Jan 2008 11:02:53 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Pavel Machek <pavel@ucw.cz>
CC: Miklos Szeredi <miklos@szeredi.hu>, akpm@linux-foundation.org,
       linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       util-linux-ng@vger.kernel.org, linuxram@us.ibm.com,
       viro@ftp.linux.org.uk, hch@infradead.org, a.p.zijlstra@chello.nl
Subject: Re: [RFC][PATCH] VFS: create /proc/<pid>/mountinfo
References: <E1JGBVq-0002Or-H1@pomaz-ex.szeredi.hu> <4792DF11.7040403@zytor.com> <E1JGVSG-0003mx-TS@pomaz-ex.szeredi.hu> <20080123134926.GB4059@ucw.cz>
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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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