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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: [RESEND v7 20/29] mm/madvise: skip PMD swap entries for MADV_COLD and MADV_PAGEOUT Date: Mon, 14 Sep 2026 05:28:10 -0700 Message-ID: <20260914122950.3283997-21-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914122950.3283997-1-usama.arif@linux.dev> References: <20260914122950.3283997-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 388BF18000F X-Stat-Signature: ko7zchkub9cwt1eonirghmwhaygkcpb6 X-HE-Tag: 1789389114-330300 X-HE-Meta: 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 th+FgWsm 4HBS8QE7BtTbosWvDKyQWrg29OSUmeBq2rtcO1c6I/BBva8Y2xGh73iz36GX8mW0kjuEs5/ixw1UrK2MnV+k1uWyrm0PsVt4hR4vtsNSWtnTaeAEHduJKMoHaYYEVxcEse1hy75C2STLsm3Td5w7GsqaTGHAJSi9Q5/yegPFe9Tj7qZaptt6UmNOqdDHbvLKngEYG/eaBwoYS9lyo4BgRhitEFQAn+kSE4qYxvAhfveBAMujT6KNeK7WBnhLltYo9fnlsfGhYe67RYPPNm4dmxckiBg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 70acb39b8b3dd..d3b5ed7e3cffb 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -385,6 +385,15 @@ 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); @@ -395,6 +404,9 @@ 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