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Wong" , "david@fromorbit.com" , "vishal.l.verma@intel.com" , "dave.jiang@intel.com" , "agk@redhat.com" , "snitzer@redhat.com" , "dm-devel@redhat.com" , "ira.weiny@intel.com" , "willy@infradead.org" , "vgoyal@redhat.com" , "linux-fsdevel@vger.kernel.org" , "nvdimm@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "linux-xfs@vger.kernel.org" Subject: Re: [dm-devel] [PATCH 0/6] dax poison recovery with RWF_RECOVERY_DATA flag Message-ID: References: <2102a2e6-c543-2557-28a2-8b0bdc470855@oracle.com> <20211028002451.GB2237511@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 04, 2021 at 09:08:41AM -0700, Dan Williams wrote: > Yes, atomic clear+write new data. The ability to atomic clear requires > either a CPU with the ability to overwrite cachelines without doing a > RMW cycle (MOVDIR64B), or it requires a device with a suitable > slow-path mailbox command like the one defined for CXL devices (see > section 8.2.9.5.4.3 Clear Poison in CXL 2.0). > > I don't know why you think these devices don't perform wear-leveling > with spare blocks? Because the interface looks so broken. But yes, apparently it's not the media management that is broken but just the inteface that fakes up byte level access. > All kernel accesses do use it. They either route to > pmem_copy_to_iter(), or like dm-writecache, call it directly. Do you > see a kernel path that does not use that helper? No, sorry. My knowledge is out of date. (nova does, but it is out of tree, and the lack of using copy_mc_to_kernel is the least of its problems)