linux-kernel - Re: blkdev_issue_flush really issues a WRITE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <4AD37790.8090404@garzik.org>
Date:	Mon, 12 Oct 2009 14:38:08 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Jeff Moyer <jmoyer@...hat.com>
CC:	Linux Kernel Mailing <linux-kernel@...r.kernel.org>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: blkdev_issue_flush really issues a WRITE_BARRIER -- is that okay?

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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/