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Re: [PATCH] block: use the request length for iov alignment
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From: |
Keith Busch |
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Subject: |
Re: [PATCH] block: use the request length for iov alignment |
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Date: |
Tue, 13 Sep 2022 15:36:42 +0100 |
On Tue, Sep 13, 2022 at 03:20:23PM +0100, Damien Le Moal wrote:
> On 2022/09/13 15:12, Keith Busch wrote:
> > On Thu, Sep 08, 2022 at 09:45:26AM -0700, Keith Busch wrote:
> >> From: Keith Busch <kbusch@kernel.org>
> >>
> >> An iov length needs to be aligned to the logical block size, which may
> >> be larger than the memory alignment.
> >
> > [cc'ing some other interested folks]
> >
> > Any thoughts on this patch? It is fixing an observed IO error when running
> > virtio-blk with the default 512b logical block size backed by a drive
> > formatted
> > with 4k logical block.
>
> The patch look OK to me, but having virtio expose a 512B LBA size for a
> backing
> device that has 4K LBAs will break all IOs if caching is turned off (direct
> IOs
> case), even if this patch is applied. No ?
Yeah, it's just the default. I don't think anyone would do that on purpose
since it's so sub-optimal from a performance stand-point. As a follow up patch,
perhaps if the logical_block_size parameter is not provided, we should default
to the backing device's block size?