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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 v9 23/32] mm/madvise: skip PMD swap entries for MADV_COLD and MADV_PAGEOUT Date: Thu, 5 Nov 2026 10:39:07 -0800 Message-ID: <20261105183940.2236717-24-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261105183940.2236717-1-usama.arif@linux.dev> References: <20261105183940.2236717-1-usama.arif@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 7o7joz4xri41crq5r18jj65dfezwp5ys X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5A7DE2000A X-HE-Tag: 1793904119-730372 X-HE-Meta: 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 1Xamn3Bc M3pf9g6zQEijp1pnKneVzTOxo2lwWE3w7DBtOBWRoWjG2mgUgp+7LmFTPxQjpkRL9rlHdqHkYhVrjCXi2li2B/8+byIxlMs55DO526pnFF6y6ac43jTiTrFrHvaIzOYymcz35yrfhXwSDFqfarbDR8NffTz2U+tePWjEQsJwZDhZKDsVmtVhxXuWSAsnR8PWbrfKyaU8xzL4N02tulUNzo2aBD/jErSG1vFwRAxUzzymSHZMgNN8VT925CC3NhboaWC2WZRExgT8t+vng7JFook2Yag== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 A swapped-out THP has no resident folio to deactivate or reclaim, which is also the conclusion the PTE path reaches when it walks the swap entries and skips every one. madvise_cold_or_pageout_pte_range() gets there the long way round: pmd_trans_huge() is false for a PMD swap entry, so it falls out of the huge branch and tries to map a PTE table that a non-present PMD does not have. The entry can also appear after that first, lockless test, so re-check under the PMD lock; otherwise a PMD that turned into a swap entry while pmd_trans_huge_lock() was being taken trips the VM_WARN_ON_ONCE() that expects a migration or device-private entry. Signed-off-by: Usama Arif --- mm/madvise.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 156290227c236..576707e303cf2 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -384,6 +384,15 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, !can_do_file_pageout(vma); #ifdef CONFIG_TRANSPARENT_HUGEPAGE + /* + * Swapped-out THPs have no resident folio to deactivate or reclaim. + * Avoid descending into or splitting a PMD swap entry. + */ + if (pmd_is_swap_entry(*pmd)) { + walk->action = ACTION_CONTINUE; + return 0; + } + if (pmd_trans_huge(*pmd)) { pmd_t orig_pmd; unsigned long next = pmd_addr_end(addr, end); @@ -394,6 +403,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, return 0; orig_pmd = *pmd; + if (pmd_is_swap_entry(orig_pmd)) + goto huge_unlock; + if (unlikely(!pmd_present(orig_pmd))) { VM_WARN_ON_ONCE(!pmd_is_migration_entry(orig_pmd) && !pmd_is_device_private_entry(orig_pmd)); -- 2.53.0-Meta