Messages in this thread | | | Subject | Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16 | From | "Martin K. Petersen" <> | Date | Wed, 16 Jul 2014 13:47:35 -0400 |
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>>>>> "Christoph" == hch@infradead org <hch@infradead.org> writes:
Christoph> Oh, we actually have devices that support WRITE SAME with Christoph> unmap, but not without? That's defintively a little strange.
Yep :(
There were several SSDs that did not want to support wearing out flash by writing gobs of zeroes and only support the UNMAP case.
Christoph> Yes, and it did this intentionally. I really wouldn't expect Christoph> devices to support WRITE SAME with UNMAP but blow up on a Christoph> WRITE SAME without it (and not just simple fail it in an Christoph> orderly way).
*sigh*
Christoph> It definitively seems odd to default to trying WRITE SAME for Christoph> unmap for a device that explicitly tells us that it doesn't Christoph> support WRITE SAME.
Maybe it's just a naming thing. I was really trying to convey no_req_write_same support, not no_write_same_10_or_16.
Christoph> Note that I'm not against your patch - I suspect forcing us Christoph> to read EVPD pages even for devices that claim to be SPC-2 Christoph> will come in useful in various scenarios.
I don't have a problem with a BLIST_PREFER_UNMAP flag or something like that. But BLIST_TRY_VPD_PAGES seems more generally useful and it does fix the problem at hand. That's why I went that route.
-- Martin K. Petersen Oracle Linux Engineering
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