linux-kernel - Re: [BUG?] possible recursive locking detected

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Message-Id: <20060727003806.def43f26.akpm@osdl.org>
Date:	Thu, 27 Jul 2006 00:38:06 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Anton Altaparmakov <aia21@....ac.uk>
Cc:	nickpiggin@...oo.com.au, eike-kernel@...tec.de,
	linux-kernel@...r.kernel.org, aia21@...tab.net
Subject: Re: [BUG?] possible recursive locking detected

On Thu, 27 Jul 2006 08:15:27 +0100
Anton Altaparmakov <aia21@....ac.uk> wrote:

> > I'm surprised ext2 is allocating with __GFP_FS set, though. Would that
> > cause any problem?
> 
> That is an ext2 bug IMO.

There is no bug.

What there is is an ill-defined set of rules.  If we want to tighten these
rules we have a choice between

a) Never enter page reclaim while holding i_mutex or

b) never take i_mutex on the page reclaim path.

Implementing a) would be a disaster.  It means that our main write()
implementation in mm/filemap.c (which holds i_mutex) wouldn't be able to
reclaim pages to satisfy the write.  And generally, we do want to use the
strongest memory allocation mode at all times.

So we'll have a better kernel if we implement b).
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