linux-kernel - Re: 2.6.22-rc3-mm1 - page

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Date:	Fri, 1 Jun 2007 03:01:29 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Mark Fasheh <mark.fasheh@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.22-rc3-mm1 - page_mkwrite() breakage

On Thu, May 31, 2007 at 04:13:54PM -0700, Mark Fasheh wrote:
> On Wed, May 30, 2007 at 11:58:23PM -0700, Andrew Morton wrote:
> >  git-ocfs2.patch
> 
> Andrew, thanks for getting that back in there.
> 
> 
> mm-fix-fault-vs-invalidate-race-for-linear-mappings.patch broke ocfs2 shared
> writable mmap. We hang on a page lock because ->page_mkwrite() is
> being called with the page already locked:
> 
> +	/*
> +	 * For consistency in subsequent calls, make the nopage_page always
> +	 * locked.
> +	 */
> +	if (unlikely(!(vma->vm_flags & VM_CAN_INVALIDATE)))
> +		lock_page(nopage_page);
> 
> It wasn't previously being called with the page lock held, intentionally.

Ah, I didn't realise you were using that yet. I expect ocfs2 is using
VM_CAN_INVALIDATE there anyway.

Hmm, this becomes easier to deal with after page_mkwrite is merged with
->fault. But for now, can we just lock the page at the do_wp_page site
as well, and change the API? All users I have seen want the page locked
there anyway...

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