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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 24/32] mm/madvise: keep PMD swap entries whole for MADV_GUARD_INSTALL/REMOVE Date: Thu, 5 Nov 2026 10:39:08 -0800 Message-ID: <20261105183940.2236717-25-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-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 45E6D20008 X-Stat-Signature: z1odxnsehtc1g8e5q9ak9x7jotquar1j 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-HE-Tag: 1793904127-300492 X-HE-Meta: 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 GhXW8hvR HcCBg3N+h/Lx7SRdQBohppJnh1ThZc7mhWhzB2wBWi1sNPDpGz9MRa2VGx75bN7Z2soCVtt+fnMVaL8J8hU2PvdynMzVkBmADU3F1VK3MXvjK5vrJQIJdytDc9FGgaLCCebwhryaPTt/2E9/EkUS8EbnDyQuOnqfQkbopX+EGfNY8T3yRzxNvWVBxxO0ndfXVGO8ym6e7TvWJ1KnFNmnSgAE1es7VhSpb4KuvY96OCRPGXVmCqEF6LJwcOk0JKRysD7/EwCK03fI40ICK7/ok2LNmLA== 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 Both callbacks test bare pmd_trans_huge(), which is false for a PMD swap entry, so they return without consuming the PMD and walk_pmd_range() splits it - only for the PTE callbacks to find the range populated and abort, or to find no guard markers and do nothing. Both already short-circuit at PMD level for a present THP. Do the same for a swapped-out one: it is just as populated, and just as free of guard markers. Signed-off-by: Usama Arif --- mm/madvise.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 576707e303cf2..f7f17efdd926d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1109,8 +1109,12 @@ static int guard_install_pmd_entry(pmd_t *pmd, unsigned long addr, { pmd_t pmdval = pmdp_get(pmd); - /* If huge return >0 so we abort the operation + zap. */ - return pmd_trans_huge(pmdval); + /* + * If huge return >0 so we abort the operation + zap. A PMD swap entry + * is a swapped-out THP: also populated, and splitting it here would + * only demote it before the zap. + */ + return pmd_trans_huge(pmdval) || pmd_is_swap_entry(pmdval); } static int guard_install_pte_entry(pte_t *pte, unsigned long addr, @@ -1249,8 +1253,12 @@ static int guard_remove_pmd_entry(pmd_t *pmd, unsigned long addr, { pmd_t pmdval = pmdp_get(pmd); - /* If huge, cannot have guard pages present, so no-op - skip. */ - if (pmd_trans_huge(pmdval)) + /* + * If huge, cannot have guard pages present, so no-op - skip. The same + * is true of a PMD swap entry, which must not be split just to discover + * there is nothing to remove. + */ + if (pmd_trans_huge(pmdval) || pmd_is_swap_entry(pmdval)) walk->action = ACTION_CONTINUE; return 0; -- 2.53.0-Meta