From mboxrd@z Thu Jan 1 00:00:00 1970 From: willy@linux.intel.com (Matthew Wilcox) Date: Sat, 5 Mar 2016 17:39:49 -0500 Subject: [PATCH] NVMe: Create discard zero quirk white list In-Reply-To: <20160304180443.GA3972@infradead.org> References: <1457113522-14099-1-git-send-email-keith.busch@intel.com> <20160304180443.GA3972@infradead.org> Message-ID: <20160305223949.GD5530@linux.intel.com> On Fri, Mar 04, 2016@10:04:43AM -0800, Christoph Hellwig wrote: > On Fri, Mar 04, 2016@10:45:22AM -0700, Keith Busch wrote: > > The NVMe specification does not require discarded blocks return zeroes on > > read, but provides that behavior as a possibility. Some applications more > > efficiently use an SSD if reads on discarded blocks were deterministically > > zero, based on the "discard_zeroes_data" queue attribute. > > Meh, indeed: > > "If a read occurs to a deallocated range, the controller shall return > all zeros, all ones, or the last data written to the associated LBA." > > time to write a TP for a bit on the identify page.. Since we have a WRITE ZEROES command, do we need this? > > There is no specification defined way to determine device behavior on > > discarded blocks, so the driver always left the queue setting disabled. We > > can only know behavior based on individual device models, so this patch > > adds a flag to the NVMe "quirk" list that vendors may set if they know > > their controller works that way. The patch also sets the new flag for one > > such known device. > > > > Suggested-by: Artur Paszkiewicz > > Signed-off-by: Keith Busch > > Not happy about this, but I guess we'll need something like this in the > long run.. > > Reviewed-by: Christoph Hellwig > > _______________________________________________ > Linux-nvme mailing list > Linux-nvme at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-nvme