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Message-ID: <20100311162707.GB19923@atrey.karlin.mff.cuni.cz> Date: Thu, 11 Mar 2010 17:27:08 +0100 From: Jan Kara <jack@...e.cz> To: Dmitry Monakhov <dmonakhov@...nvz.org> Cc: linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz> Subject: Re: [PATCH] ext4: fix io-barrier logic for external journal case > We have to submit barrier before we start journal commit process. > otherwise transaction may be committed before data flushed to disk. > There is no difference from performance of view, but definitely > fsync becomes more correct. > > If jbd2_log_start_commit return 0 then it means that transaction > was already committed. So we don't have to issue barrier for > ordered mode, because it was already done during commit. Umm, we have to - when a file has just been rewritten (i.e. no block allocation), then i_datasync_tid is not updated and thus we won't commit any transaction as a part of fdatasync (and that is correct because there are no metadata that need to be written for that fdatasync). But we still have to flush disk caches with data submitted by filemap_fdatawrite_and_wait. > By unknown reason we ignored ret val from jbd2_log_wait_commit() > so even in case of EIO fsync will succeed. I just forgot jbd2_log_wait_commit can return a failure... 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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