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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, Usama Arif Subject: [PATCH v7 08/29] mm: recognize PMD swap entries in the softleaf layer Date: Mon, 14 Sep 2026 04:42:00 -0700 Message-ID: <20260914114320.12988-9-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914114320.12988-1-usama.arif@linux.dev> References: <20260914114320.12988-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BB33E40009 X-Stat-Signature: iuqoonki9oopbgruqdcijspjzds7pjky X-Rspam-User: X-HE-Tag: 1789386246-209379 X-HE-Meta: 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 6G0qhmda f8lNvddvGzbJgf9x63nQlIesh7Vda0byIm8GylQVff/wjrQExa8mwRmYgYBM/5PgGcGh+cYRJMC7jvxWqnyCrt5IX5/careo0pOHAH6clCE8scUtCa39GT6N/b02F3UJC1Bm/MAyyV6KCr4Co/vQ1oqbqOSpUaD399WSZibJiqkttoganxCGsohJMYC+lYExXLnlESM4GwD4lVlfjE2yhNIZTwrj73vyoER6jeIaAMtAisGY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- include/linux/leafops.h | 40 ++++++++++++++++++++++++++++------------ include/linux/pgtable.h | 17 +++++++++++++++++ 2 files changed, 45 insertions(+), 12 deletions(-) diff --git a/include/linux/leafops.h b/include/linux/leafops.h index 7c13c58a5e218..ce176c78cefd4 100644 --- a/include/linux/leafops.h +++ b/include/linux/leafops.h @@ -98,10 +98,9 @@ static inline softleaf_t softleaf_from_pmd(pmd_t pmd) if (pmd_present(pmd) || pmd_none(pmd)) return softleaf_mk_none(); - if (pmd_swp_soft_dirty(pmd)) - pmd = pmd_swp_clear_soft_dirty(pmd); - if (pmd_swp_uffd(pmd)) - pmd = pmd_swp_clear_uffd(pmd); + pmd = pmd_swp_clear_soft_dirty(pmd); + pmd = pmd_swp_clear_uffd(pmd); + pmd = pmd_swp_clear_exclusive(pmd); arch_entry = __pmd_to_swp_entry(pmd); /* Temporary until swp_entry_t eliminated. */ @@ -634,18 +633,29 @@ static inline bool pmd_is_migration_entry(pmd_t pmd) */ static inline bool softleaf_is_valid_pmd_entry(softleaf_t entry) { - /* Only device private, migration entries valid for PMD. */ return softleaf_is_device_private(entry) || - softleaf_is_migration(entry); + softleaf_is_migration(entry) || + softleaf_is_swap(entry); +} + +/** + * pmd_is_swap_entry() - Does this PMD entry encode an actual swap entry? + * @pmd: PMD entry. + * + * Returns: true if the PMD encodes a swap entry, otherwise false. + */ +static inline bool pmd_is_swap_entry(pmd_t pmd) +{ + return softleaf_is_swap(softleaf_from_pmd(pmd)); } /** * pmd_is_valid_softleaf() - Is this PMD entry a valid softleaf entry? * @pmd: PMD entry. * - * PMD leaf entries are valid only if they are device private or migration - * entries. This function asserts that a PMD leaf entry is valid in this - * respect. + * PMD leaf entries are valid only if they are device private, migration, + * or swap entries. This function asserts that a PMD leaf entry is valid + * in this respect. * * Returns: true if the PMD entry is a valid leaf entry, otherwise false. */ @@ -660,10 +670,12 @@ static inline bool pmd_is_valid_softleaf(pmd_t pmd) * pmd_softleaf_to_folio() - Convert the PMD softleaf entry to a folio. * @pmd: PMD entry. * - * The PMD entry is expected to be a valid PMD softleaf entry. + * The PMD entry is expected to be a valid PMD softleaf entry that references a + * PFN, that is a migration or device private entry. A PMD swap entry is a valid + * softleaf entry but encodes swap slots rather than a PFN, so it has no folio. * - * Returns: the folio the softleaf entry references if this is a valid softleaf - * entry, otherwise NULL. + * Returns: the folio the softleaf entry references, or NULL if the entry is not + * a valid PMD softleaf entry or does not reference a PFN. */ static inline struct folio *pmd_softleaf_to_folio(pmd_t pmd) { @@ -673,6 +685,10 @@ static inline struct folio *pmd_softleaf_to_folio(pmd_t pmd) VM_WARN_ON_ONCE(true); return NULL; } + if (!softleaf_has_pfn(entry)) { + VM_WARN_ON_ONCE(true); + return NULL; + } return softleaf_to_folio(entry); } diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index e3c8ab96941c5..3f955f836abfe 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1917,6 +1917,23 @@ static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd) } #endif +#ifndef CONFIG_ARCH_HAS_PMD_SOFTLEAVES +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) +{ + return pmd; +} + +static inline bool pmd_swp_exclusive(pmd_t pmd) +{ + return false; +} + +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) +{ + return pmd; +} +#endif + #ifndef __HAVE_PFNMAP_TRACKING /* * Interfaces that can be used by architecture code to keep track of -- 2.53.0-Meta