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[142.167.56.70]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7d09a0fa38fsm842635185a.35.2025.06.03.06.37.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Jun 2025 06:37:00 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1uMRp5-00000001h5Y-2rWO; Tue, 03 Jun 2025 10:36:59 -0300 Date: Tue, 3 Jun 2025 10:36:59 -0300 From: Jason Gunthorpe To: Alistair Popple Cc: linux-mm@kvack.org, gerald.schaefer@linux.ibm.com, dan.j.williams@intel.com, willy@infradead.org, david@redhat.com, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, zhang.lyra@gmail.com, debug@rivosinc.com, bjorn@kernel.org, balbirs@nvidia.com, lorenzo.stoakes@oracle.com, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-cxl@vger.kernel.org, dri-devel@lists.freedesktop.org, John@groves.net Subject: Re: [PATCH 03/12] mm/pagewalk: Skip dax pages in pagewalk Message-ID: <20250603133659.GD386142@ziepe.ca> References: <1799c6772825e1401e7ccad81a10646118201953.1748500293.git-series.apopple@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1799c6772825e1401e7ccad81a10646118201953.1748500293.git-series.apopple@nvidia.com> On Thu, May 29, 2025 at 04:32:04PM +1000, Alistair Popple wrote: > Previously dax pages were skipped by the pagewalk code as pud_special() or > vm_normal_page{_pmd}() would be false for DAX pages. Now that dax pages are > refcounted normally that is no longer the case, so add explicit checks to > skip them. > > Signed-off-by: Alistair Popple > --- > include/linux/memremap.h | 11 +++++++++++ > mm/pagewalk.c | 12 ++++++++++-- > 2 files changed, 21 insertions(+), 2 deletions(-) But why do we want to skip them? Like hmm uses pagewalk and it would like to see DAX pages? I guess it makes sense from the perspective of not changing things, but it seems like a comment should be left behind explaining that this is just for legacy reasons until someone audits the callers. Jason