linux-ext4 - Re: [PATCH] ext4: Rewrite ext4_page

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Message-ID: <20110608141018.GH30037@thunk.org>
Date:	Wed, 8 Jun 2011 10:10:18 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: Rewrite ext4_page_mkwrite() to return locked page

Ping?

					- Ted

On Sun, Jun 05, 2011 at 10:17:54PM -0400, Ted Ts'o wrote:
> On Mon, May 30, 2011 at 05:03:49PM +0200, Jan Kara wrote:
> > ext4_page_mkwrite() does not return page locked. This makes it hard
> > to avoid races with filesystem freezing code (so that we don't leave
> > writeable page on a frozen fs) or writeback code (so that we allow page
> > to be stable during writeback).
> > 
> > Also the current code uses i_alloc_sem to avoid races with truncate but that
> > seems to be the wrong locking order according to lock ordering documented in
> > mm/rmap.c.
> > 
> > Also add a check for frozen filesystem so that we don't busyloop in page fault
> > when the filesystem is frozen.
> > 
> > Signed-off-by: Jan Kara <jack@...e.cz>
> 
> I'm not sure this commit description is accurate --- or I'm horribly
> confused.
> 
> The old code was in fact returning the page locked --- I assume you're
> referring to lock_page(page) (which is called right before the normal
> path return).  So what am I missing?
> 
> 							- Ted
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