Messages in this thread | | | Date | Thu, 31 May 2007 12:21:31 -0700 (PDT) | From | david@lang ... | Subject | Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. |
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On Thu, 31 May 2007, Jens Axboe wrote:
> On Thu, May 31 2007, Phillip Susi wrote: >> David Chinner wrote: >>> That sounds like a good idea - we can leave the existing >>> WRITE_BARRIER behaviour unchanged and introduce a new WRITE_ORDERED >>> behaviour that only guarantees ordering. The filesystem can then >>> choose which to use where appropriate.... >> >> So what if you want a synchronous write, but DON'T care about the order? >> They need to be two completely different flags which you can choose >> to combine, or use individually. > > If you have a use case for that, we can easily support it as well... > Depending on the drive capabilities (FUA support or not), it may be > nearly as slow as a "real" barrier write.
true, but a "real" barrier write could have significant side effects on other writes that wouldn't happen with a synchronous wrote (a sync wrote can have other, unrelated writes re-ordered around it, a barrier write can't)
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