From: Ted Ts'o <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH] ext4: Rewrite ext4_page_mkwrite() to return locked page
Date: Sun, 5 Jun 2011 22:17:54 -0400 [thread overview]
Message-ID: <20110606021754.GA7180@thunk.org> (raw)
In-Reply-To: <1306767829-27580-1-git-send-email-jack@suse.cz>
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@suse.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
next prev parent reply other threads:[~2011-06-06 2:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-30 15:03 [PATCH] ext4: Rewrite ext4_page_mkwrite() to return locked page Jan Kara
2011-06-06 2:17 ` Ted Ts'o [this message]
2011-06-08 14:10 ` Ted Ts'o
2011-06-08 14:55 ` Jan Kara
2011-06-20 2:53 ` Ted Ts'o
2011-06-20 10:38 ` Jan Kara
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