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Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com Subject: Re: [RESEND v7 08/29] mm: recognize PMD swap entries in the softleaf layer Message-ID: References: <20260914122950.3283997-1-usama.arif@linux.dev> <20260914122950.3283997-9-usama.arif@linux.dev> 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: <20260914122950.3283997-9-usama.arif@linux.dev> On Mon, Sep 14, 2026 at 05:27:58AM -0700, Usama Arif wrote: > Reclaim splits a PMD-mapped anonymous THP into PTE-level swap entries > before unmapping it, so an ordinary swap entry has never had to appear in a > PMD. Later patches install one there instead, and the softleaf layer is > where every consumer decodes non-present PMDs. > > Accept swap entries as valid PMD softleaves and add pmd_is_swap_entry(). > A swap entry carries no PFN, so make pmd_softleaf_to_folio() warn and > return NULL rather than interpret a swap offset as a page frame number. > > Unlike migration and device-private entries, a PMD swap entry can also > carry the swap-exclusive marker, which softleaf_from_pmd() has to strip > before decoding. Strip all three overlays unconditionally while we are > here: each clear is a plain bit clear, so testing first only buys a branch. > > Signed-off-by: Usama Arif Reviewed-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov