* blkdev_issue_flush really issues a WRITE_BARRIER -- is that okay?
@ 2009-10-12 17:31 Jeff Moyer
2009-10-12 18:38 ` Jeff Garzik
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Moyer @ 2009-10-12 17:31 UTC (permalink / raw)
To: Linux Kernel Mailing; +Cc: Jens Axboe
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?
My apologies if this has been discussed before.
Thanks!
Jeff
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: blkdev_issue_flush really issues a WRITE_BARRIER -- is that okay?
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
0 siblings, 0 replies; 2+ messages in thread
From: Jeff Garzik @ 2009-10-12 18:38 UTC (permalink / raw)
To: Jeff Moyer; +Cc: Linux Kernel Mailing, Jens Axboe
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
^ permalink raw reply [flat|nested] 2+ messages in thread
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