Messages in this thread | | | Date | Tue, 12 May 2009 09:53:05 +0900 | From | Tejun Heo <> | Subject | Re: [dm-devel] Re: [PATCH 1/3] block: add alt_size |
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Konrad Rzeszutek wrote: > .. snip .. >>> Also, values with magic block counts, while there is no way to get the >>> blocksize with the same interface, are pretty weird. I think the >>> current "size" attribute is just a bug. >> Logical block size is fixed at 512 bytes. Offset and size are always >> represented in multiples of 512 bytes and only get converted to >> hardware block size in the lld. > > That interpretation is at odds with the work that Martin Peterson is > doing with the 4K support. In the e-mail titled: "Re: [PATCH 4 of 8] sd: > Physical block size and alignment support", > Message-ID:<yq1ab67b51p.fsf@sermon.lab.mkp.net> he says: > > " > Konrad> about what a 'logical block', and 'physical block' is > Konrad> vs. 'hardware sector' ? > > Well, another item on my todo list is to kill the notion of hardware > sector completely. The protocols have been referring to logical blocks > for ages. > > It hasn't been a big problem until now because logical block size has > been equal to the hardware sector size. That's no longer a valid > assumption. > " > > Are the ATA/SCSI/etc specs at odds with each other about this?
Hardware specs aren't of concern here. The logical block concept is there simply to give 9 bit addressing advantage, nothing more, nothing less. If hardware's sector size doesn't match it, the lld should be mapping the sector addresses and sizes and cdrom and a few other drives have been doing that for ages. There's nothing new about devices with sectors larger than 512 bytes.
Thanks.
-- tejun
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