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Date: Wed, 16 Jul 2014 18:50:31 +0000 From: James Bottomley <jbottomley@...allels.com> To: "martin.petersen@...cle.com" <martin.petersen@...cle.com> CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "hch@...radead.org" <hch@...radead.org>, "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>, "apw@...onical.com" <apw@...onical.com>, "kys@...rosoft.com" <kys@...rosoft.com>, "stable@...r.kernel.org" <stable@...r.kernel.org>, "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>, "ohering@...e.com" <ohering@...e.com>, "jasowang@...hat.com" <jasowang@...hat.com> Subject: Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16 On Wed, 2014-07-16 at 14:45 -0400, Martin K. Petersen wrote: > >>>>> "James" == James Bottomley <jbottomley@...allels.com> writes: > > >> 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. > > James> Hang on ... unless we apply Christoph or my fix, we'll get the > James> same issue with every raid driver (that's about 10 I think) that > James> set no_write_same when they hit a >2TB RAID volume, > > no_write_same is set for all the RAID controller drivers (54b2b50c20a6). > > If a WRITE SAME(10/16) command fails and the UNMAP bit is not set we'll > set no_write_same=1 and disable REQ_WRITE_SAME support. > > If a WRITE SAME(10/16) command fails and the UNMAP bit is set we'll > disable REQ_DISCARD support. > > Not sure where the 10 vs. 16 byte 2TB limitation comes into play here? It's the code we identified in sd.c:read_capacity_16(): if (buffer[14] & 0x80) { /* LBPME */ sdkp->lbpme = 1; if (buffer[14] & 0x40) /* LBPRZ */ sdkp->lbprz = 1; sd_config_discard(sdkp, SD_LBP_WS16); } If the inquiry shows LBPME set, we'll do write same regardless of the no_write_same bit. That's why for SPC-2 devices it only shows up on >2TB devices because they force RC16. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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