linux-ext4 - Re: [PATCH 3/3] ext4: Block mmapped writes while the fs is frozen

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Date:	Wed, 18 May 2011 17:25:32 +0200
From:	Jan Kara <jack@...e.cz>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 3/3] ext4: Block mmapped writes while the fs is frozen

On Wed 18-05-11 09:03:27, Eric Sandeen wrote:
> On 5/18/11 3:07 AM, Christoph Hellwig wrote:
> > On Wed, May 18, 2011 at 09:56:14AM +0200, Jan Kara wrote:
> >> __block_page_mkwrite() and return some error value (EAGAIN translating to
> >> VM_FAULT_RETRY would look logical, I just have to think off better error
> >> value for VM_FAULT_NOPAGE). But vfs_check_frozen() cannot be in
> >> __block_page_mkwrite() since ext4 needs to call that with a transaction
> >> started so that would create a deadlock and we need to call
> >> vfs_check_frozen() somewhere so that we don't busyloop.
> >>
> >> I can call vfs_check_frozen() inside block_page_mkwrite() but it would be a
> >> bit surprising difference from __block_page_mkwrite() to me. Not sure what
> >> the cleanest solution would be here...
> > 
> > block_page_mkwrite is supposed to be used directly by filesystems and
> > do all the right things.  IIRC Eric even mentioned he added
> > vfs_check_frozen to it for RHEL, but forgot to push it upstream.
> 
> Well, I tried, but it was rejected IIRC.  Still, mea culpa....
> 
> I can resurrect what I did for RHEL5 and repost if desired...
  I've just submitted second version of the patch series. So please check
whether it does all you need... Thanks.

									Honza
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