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[2003:d8:2f03:5b00:f549:a879:b2d3:73ee]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-450d800671csm12953125e9.30.2025.05.30.02.37.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 May 2025 02:37:22 -0700 (PDT) Message-ID: <371b8fdd-129d-4fe3-bbc7-f0a1bc433b30@redhat.com> Date: Fri, 30 May 2025 11:37:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/12] mm: Convert pXd_devmap checks to vma_is_dax To: Alistair Popple , linux-mm@kvack.org Cc: gerald.schaefer@linux.ibm.com, dan.j.williams@intel.com, jgg@ziepe.ca, willy@infradead.org, 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 References: <224f0265027a9578534586fa1f6ed80270aa24d5.1748500293.git-series.apopple@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 8bh6cjxxw5569151mtfefpchrm9q1ojd X-Rspamd-Queue-Id: 8ED9BA000F X-Rspamd-Server: rspam11 X-HE-Tag: 1748597847-464223 X-HE-Meta: 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 +caZxFKV 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 29.05.25 08:32, Alistair Popple wrote: > Currently dax is the only user of pmd and pud mapped ZONE_DEVICE > pages. Therefore page walkers that want to exclude DAX pages can check > pmd_devmap or pud_devmap. However soon dax will no longer set PFN_DEV, > meaning dax pages are mapped as normal pages. > > Ensure page walkers that currently use pXd_devmap to skip DAX pages > continue to do so by adding explicit checks of the VMA instead. > > Signed-off-by: Alistair Popple > --- > fs/userfaultfd.c | 2 +- > mm/hmm.c | 2 +- > mm/userfaultfd.c | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index 22f4bf9..de671d3 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -304,7 +304,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, > goto out; > > ret = false; > - if (!pmd_present(_pmd) || pmd_devmap(_pmd)) > + if (!pmd_present(_pmd) || vma_is_dax(vmf->vma)) > goto out; > > if (pmd_trans_huge(_pmd)) { > diff --git a/mm/hmm.c b/mm/hmm.c > index 082f7b7..db12c0a 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -429,7 +429,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, > return hmm_vma_walk_hole(start, end, -1, walk); > } > > - if (pud_leaf(pud) && pud_devmap(pud)) { > + if (pud_leaf(pud) && vma_is_dax(walk->vma)) { > unsigned long i, npages, pfn; > unsigned int required_fault; > unsigned long *hmm_pfns; > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index e0db855..133f750 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -1791,7 +1791,7 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, > > ptl = pmd_trans_huge_lock(src_pmd, src_vma); > if (ptl) { > - if (pmd_devmap(*src_pmd)) { > + if (vma_is_dax(src_vma)) { > spin_unlock(ptl); > err = -ENOENT; > break; I assume we could also just refuse dax folios, right? If we decide to check VMAs, we should probably check earlier. But I wonder, what about anonymous non-dax pages in COW mappings? Is it possible? Not supported? If supported, checking the actual folio would be the right thing to do. -- Cheers, David / dhildenb