linux-kernel - Re: [patch 00/27] [rfc] vfs scalability patchset

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Message-ID: <20090425193133.GB8633@ZenIV.linux.org.uk>
Date:	Sat, 25 Apr 2009 20:31:33 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Christoph Hellwig <hch@...radead.org>, npiggin@...e.de,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 00/27] [rfc] vfs scalability patchset

On Sat, Apr 25, 2009 at 12:08:16PM -0700, Eric W. Biederman wrote:

> Can we?  My first glance at that code I asked myself if we could examine
> i_writecount, instead of going to the file. My impression was that we
> were deliberately only counting persistent write references from files

No, there's nothing deliberate about that.  The code is simply wrong;
some of that crap had been fixed with mnt_want_write series, but
the rest...

> instead of transient write references.  As only the persistent write
> references matter.  Transient write references can at least in theory
> be flushed as the filesystem is remounting read-only.

No.  It's far too painful to do and no fs is doing that.  You are looking
for deliberate behaviour in a place where we have a half-fixed pile of races.
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