linux-ext4 - Re: [PATCH] ext3: enable cache flush in ext3_sync

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Message-ID: <20090908130438.GA2528@atrey.karlin.mff.cuni.cz>
Date:	Tue, 8 Sep 2009 15:04:38 +0200
From:	Jan Kara <jack@...e.cz>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Christoph Hellwig <hch@....de>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext3: enable cache flush in ext3_sync_file

> Christoph Hellwig wrote:
> > We need to flush the write cache unconditionally in ->fsync, otherwise
> > writes into already allocated blocks can get lost.  Writes into fully
> > allocated files are very common when using disk images for
> > virtualization, and without this fix can easily lose data after
> > an fdatasync, which is the typical implementation for a cache flush on
> > the virtual drive.
> > 
> > 
> > Signed-off-by: Christoph Hellwig <hch@....de>
> 
> Given that I tried to do the same thing 1.5 years ago (though not quite
> correctly) ...
> 
> Acked-by: Eric Sandeen <sandeen@...hat.com>
  But would the patch below be better? When we force a transaction
commit we don't have to flush caches again. Or am I missing something?

								Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs

View attachment "0001-ext3-Flush-disk-caches-on-fsync-when-needed.patch" of type "text/x-diff" (1629 bytes)