From: Jeff Garzik <jeff@garzik.org>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Linux Kernel Mailing <linux-kernel@vger.kernel.org>,
Jens Axboe <jens.axboe@oracle.com>
Subject: Re: blkdev_issue_flush really issues a WRITE_BARRIER -- is that okay?
Date: Mon, 12 Oct 2009 14:38:08 -0400 [thread overview]
Message-ID: <4AD37790.8090404@garzik.org> (raw)
In-Reply-To: <x49hbu4semq.fsf@segfault.boston.devel.redhat.com>
On 10/12/2009 01:31 PM, Jeff Moyer wrote:
> Hi,
>
> While looking though Christoph's patch to call blkdev_issue_flush for
> fsync on block devices, I noticed that it only issues a WRITE_BARRIER.
> I don't see how that guarantees that data is on stable storage. Am I
> missing something? Shouldn't this translate to a FLUSH CACHE or
> SYNCHRONIZE CACHE command?
Barriers are a high level primitive that exist at the block layer level.
Lower level storage drivers then convert barriers to a hardware-specific
low level primitive such as SYNCHRONIZE CACHE or FUA.
Jeff
prev parent reply other threads:[~2009-10-12 18:38 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-12 17:31 blkdev_issue_flush really issues a WRITE_BARRIER -- is that okay? Jeff Moyer
2009-10-12 18:38 ` Jeff Garzik [this message]
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