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Message-ID: <20090826160231.GA28867@atrey.karlin.mff.cuni.cz> Date: Wed, 26 Aug 2009 18:02:31 +0200 From: Jan Kara <jack@...e.cz> To: Theodore Tso <tytso@....edu> Cc: Andreas Dilger <adilger@....com>, Ric Wheeler <rwheeler@...hat.com>, Christian Fischer <Christian.Fischer@...terngraphics.com>, linux-ext4@...r.kernel.org Subject: Re: Enable asynchronous commits by default patch revoked? > On Mon, Aug 24, 2009 at 05:43:36PM -0600, Andreas Dilger wrote: > > Without transaction checksums waiting on all of the blocks together > > is NOT safe. If the commit record is on disk, but the rest of the > > transaction's blocks are not then during replay it may cause garbage > > to be written from the journal into the filesystem metadata. > > Yes, I *said* that we can only wait on all of the blocks together with > the commit record when doing journal checksums. Sorry if I didn't > make that clear enough. I suppose we talk about the case when write caches are turned off and we use barrier=0 (because case barrier=1 does not really care about when we wait for the blocks from the correctness POV - at least according to Documentation/block/barrier.txt). In that case, you have to wait for *data* blocks before writing the commit block because you have no checksumming of those... Honza -- Jan Kara <jack@...e.cz> SuSE CR Labs -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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