From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24CCF489FAA for ; Fri, 2 Oct 2026 09:57:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935041; cv=none; b=NmOP722rA8ejR6sHS1NEof29IvjVASSzJAiB64yXs+KG7NEyPssH2ka4kAEmjMYTLIM8sv0c/YLbkziZtFEx4vb8UDQTrCbzqXJD2CNCoub7d0Q1hHUiLD2kLZlqJqmZRfJ/C9hCZOLD7kV2Wm5bRUx7IkM9Ll5AJRHvkmdatYE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935041; c=relaxed/simple; bh=PmpEBPMCGBePeR65tGhRvp39CU+cDN/bw2BxnAbshOU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BDQAMHWmO0VkMeIAC8Q6fTxuws0EfUYY+okOXxXvsc9WWFTQGwfQwKeD66HmzISFwSUNel8Sl1QJjBDNIyDaR50Z4X0Nl0C6NJwEBa8RaleyYCqTaP93N/vdc0mFwhvCn7J+V8+al7oX3RxZnrqxQD5Mfz8CYOu+VIHbcO8pfbk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=WrgzEM+W; arc=none smtp.client-ip=95.215.58.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="WrgzEM+W" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=PmpEBPMCGBePeR65tGhRvp39CU+cDN/bw2BxnAbshOU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790935037; v=1; x=1791539837; b=WrgzEM+WqqX2w4ih9Nppu1PuXJh6gY3cTNdLTTt0viSvXSQRPpAig7v1uKhVJqNOHSX/Od0j KhKBXStEwPvEqoDfe8NPKUSgnrp2VRopSRcF0iq9HarykFtqh4qqEhhhg7nOKuTwJwusBApcWcV 9ZJGJPOoCWVvWiUrqV6hCHn8= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta10.migadu.com with ESMTPS id 46590f4179113d43; Fri, 02 Oct 2026 09:57:17 +0000 X-Mizu-Trace-ID: 46590f4179113d43 X-Migadu-Flow: FLOW_OUT From: Usama Arif To: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , Liam R. 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 v8 22/30] mm/madvise: keep PMD swap entries whole for MADV_GUARD_INSTALL/REMOVE Date: Fri, 2 Oct 2026 02:52:36 -0700 Message-ID: <20261002095503.3585565-23-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261002095503.3585565-1-usama.arif@linux.dev> References: <20261002095503.3585565-1-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-Transfer-Encoding: 8bit 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 d3b5ed7e3cffb..64019668d69fb 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1269,8 +1269,12 @@ 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, @@ -1409,8 +1413,12 @@ 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