From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C7DC61088E48 for ; Wed, 18 Mar 2026 22:30:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 575816B0352; Wed, 18 Mar 2026 18:30:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 460CC6B0354; Wed, 18 Mar 2026 18:30:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23E416B0355; Wed, 18 Mar 2026 18:30:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 07BAD6B0352 for ; Wed, 18 Mar 2026 18:30:07 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id C70B51B6F94 for ; Wed, 18 Mar 2026 22:30:06 +0000 (UTC) X-FDA: 84560628012.05.68CAEDE Received: from mail-ot1-f43.google.com (mail-ot1-f43.google.com [209.85.210.43]) by imf12.hostedemail.com (Postfix) with ESMTP id EBD2940012 for ; Wed, 18 Mar 2026 22:30:04 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=Dv36+IVe; spf=pass (imf12.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.210.43 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773873005; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2la7S1lv8SZ13es345xjBt9aiwYWClPAry0jC6dTWYc=; b=KodaouJttsNtuFNx1V4NYYEvqExDjLr4G/JgdAm6ACXMwvva6loSer3Av8cfBGK3/eCZD4 +GFs7elfHDUdjd2EB8GWQgpdvUW8qe+vtJdL9GVcRzVMnqn0PrDFtMkloumIY75bUbQPLL ul9Da0I+UNFsQwAprSieB50MUYUjnBQ= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=Dv36+IVe; spf=pass (imf12.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.210.43 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773873005; a=rsa-sha256; cv=none; b=sjD7kHEjwLGHhB1KReh1SRtb1uIW3CDf15XyQGJeO6TaOjr77++F+qiPClWHxiC58tHELZ H3YUVH3pfGS8x1IobFpWs0wwujdV6y4OR2oxJCg2Xbgkg/mAi6MgL5+NYO42S1xD1CdkJf GQPpR5VOayfb0m5cXj5Q4eHSCcgKefk= Received: by mail-ot1-f43.google.com with SMTP id 46e09a7af769-7d743cd9e5bso238398a34.2 for ; Wed, 18 Mar 2026 15:30:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773873004; x=1774477804; darn=kvack.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=2la7S1lv8SZ13es345xjBt9aiwYWClPAry0jC6dTWYc=; b=Dv36+IVe3La/oriCIsRzysoXX07CnpPxgAW5SY34+ZdPpFdiOXmumLVh8o4bP0ueXp zf89QQc0rkRb1+pNCSaZ81bDOB40O4O5du6aliJsehDpJBVVLec7mhoK/OhZMLke1Ja4 vHkP5WTmohgrZoH+iaFBcHmgOyjCkbG/uZOoo/t0OfjPh9bqWehFIlcW5sOxIawjqS2H C5OdRjptuZdk6wxp0DStVYt8GJLg6FrQhcjYOmsQ+sR8c4G08hHQAupC4/udFqk0/flZ is4Q9jRpUUWbZ0gvPyROpmKG1sg/0JC1DxiWwlOgipfY6a3wIP1+nN1zW0f4xruJ4laG NZjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1773873004; x=1774477804; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=2la7S1lv8SZ13es345xjBt9aiwYWClPAry0jC6dTWYc=; b=Vn2xUWJxKxtNq202ikZwB4QnNzBBgJcMRVRCcH14UDKVTb7fshEiWon4hAzGol7H9k hmNiA4GyRFxjQp7S2wRXOtj1YUExN4RnP/5HiL3eBUsg+wpYeWbXXe0JcRFIBdeo3b91 0+CQ/SjwT2OnaL3IKs6WO4EooYi0/y/SvUtKZcSoDSmtWpqDxotToIwHBnHv+7W6LZ2z p5PuttvNDTw+FWWhMlwl2Lcng5ymYPBtGJfl8KjyOY4CB4M+biKCC1pQ4DW5Y2k0qoRL fm5Nh4k22CXsPew9jXduuIS3c3uuoQyht6E5sWn8FHlypqT/alu06MXcZuvZRBUe95Qy 1nBA== X-Forwarded-Encrypted: i=1; AJvYcCVNQ2llz3gnPCiBmV7ykNlWp6ezhCA8AdV9wKNPWO4YqL/VELr+uIvAsri/Sbh2aCx2r0IJJNfH7A==@kvack.org X-Gm-Message-State: AOJu0YzbRdSo8QyxXHUKNZbXiwdyZSsrLgiwY9u9bAeXtggXDpfIi8AG E1FO4190WACGXAL1f55P/RCie71qM8cZobF+ZUZFBTS+DcympvsUNUkk X-Gm-Gg: ATEYQzw6++O8qiWbp/iVHpcK+z0JQr3IpkZW0zu6mKjfICq3U1r+BWWvuhWe53Rfu2C y0yjQRTXL/0uwWQ19IPM5oFLBdojXDBd6KO+iR4uxj5RqBoTmok2Y8Gl7UkBePslfw6keH8YRx0 HouaqzVyBAGzWhFUN/+jDPqQ2O+xk1fOlc6SC4xIY2759jARxZYy00Q/n7OJowK1KazH8lkfMqg 9g9str7lQ9GkyicebzMMFaadMt8xKN5cGehBH1MSDyUukvDB/EputEUITo1Js52YdFKo4uUSUlj 2E1WktfRpR34g93WG0u8LuCK7+Zu0rpSgX/op4cfRkXaZr9Y9KUmApEuBZHl/udMe8cz+CLfgie BBw9vdikSFOqX8B7SFAln7FKqnqqSp4/p5z/2QCYhb+ib5POkcA24HP2cJ3IhjUHBQ0kBJ3X7vF K08T+YwZGl2XBaBVgwY9XDkWmAtTI0MV6rkqmbxVE/scW4 X-Received: by 2002:a05:6830:498b:b0:7d4:96c3:3f97 with SMTP id 46e09a7af769-7d7ca566cf8mr3460497a34.2.1773873003460; Wed, 18 Mar 2026 15:30:03 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:6::]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d7c9be847fsm3020992a34.27.2026.03.18.15.30.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 15:30:02 -0700 (PDT) From: Nhat Pham To: kasong@tencent.com Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, bhe@redhat.com, byungchul@sk.com, cgroups@vger.kernel.org, chengming.zhou@linux.dev, chrisl@kernel.org, corbet@lwn.net, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, lenb@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mhocko@suse.com, muchun.song@linux.dev, npache@redhat.com, nphamcs@gmail.com, pavel@kernel.org, peterx@redhat.com, peterz@infradead.org, pfalcato@suse.de, rafael@kernel.org, rakie.kim@sk.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, tglx@kernel.org, vbabka@suse.cz, weixugc@google.com, ying.huang@linux.alibaba.com, yosry.ahmed@linux.dev, yuanchu@google.com, zhengqi.arch@bytedance.com, ziy@nvidia.com, kernel-team@meta.com, riel@surriel.com Subject: [PATCH v4 05/21] mm/swap: add a new function to check if a swap entry is in swap cached. Date: Wed, 18 Mar 2026 15:29:36 -0700 Message-ID: <20260318222953.441758-6-nphamcs@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260318222953.441758-1-nphamcs@gmail.com> References: <20260318222953.441758-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: EBD2940012 X-Rspamd-Server: rspam07 X-Stat-Signature: jpsjse8zx6xsn5xw3rgpwrch7q7mtym1 X-Rspam-User: X-HE-Tag: 1773873004-336631 X-HE-Meta: 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 okXvAsfM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Userfaultfd checks whether a swap entry is in swapcache. This is currently done by directly looking at the swapfile's swap map - however, the swap cached state will soon be managed at the virtual swap layer. Abstract away this function. Signed-off-by: Nhat Pham --- include/linux/swap.h | 6 ++++++ mm/swapfile.c | 15 +++++++++++++++ mm/userfaultfd.c | 3 +-- 3 files changed, 22 insertions(+), 2 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 3da637b218baf..f91a442ac0e82 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -435,6 +435,7 @@ void free_swap_and_cache_nr(swp_entry_t entry, int nr); int __swap_count(swp_entry_t entry); bool swap_entry_swapped(struct swap_info_struct *si, swp_entry_t entry); int swp_swapcount(swp_entry_t entry); +bool is_swap_cached(swp_entry_t entry); /* Swap cache API (mm/swap_state.c) */ static inline unsigned long total_swapcache_pages(void) @@ -554,6 +555,11 @@ static inline int swp_swapcount(swp_entry_t entry) return 0; } +static inline bool is_swap_cached(swp_entry_t entry) +{ + return false; +} + static inline int folio_alloc_swap(struct folio *folio) { return -EINVAL; diff --git a/mm/swapfile.c b/mm/swapfile.c index 46da28c533bbe..0471a965f222b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -194,6 +194,21 @@ static bool swap_only_has_cache(struct swap_info_struct *si, return true; } +/** + * is_swap_cached - check if the swap entry is cached + * @entry: swap entry to check + * + * Check swap_map directly to minimize overhead, READ_ONCE is sufficient. + * + * Returns true if the swap entry is cached, false otherwise. + */ +bool is_swap_cached(swp_entry_t entry) +{ + struct swap_info_struct *si = __swap_entry_to_info(entry); + + return READ_ONCE(si->swap_map[swp_offset(entry)]) & SWAP_HAS_CACHE; +} + static bool swap_is_last_map(struct swap_info_struct *si, unsigned long offset, int nr_pages, bool *has_cache) { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 25f89eba0438c..98be764fb3ecd 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1190,7 +1190,6 @@ static int move_swap_pte(struct mm_struct *mm, struct vm_area_struct *dst_vma, * Check if the swap entry is cached after acquiring the src_pte * lock. Otherwise, we might miss a newly loaded swap cache folio. * - * Check swap_map directly to minimize overhead, READ_ONCE is sufficient. * We are trying to catch newly added swap cache, the only possible case is * when a folio is swapped in and out again staying in swap cache, using the * same entry before the PTE check above. The PTL is acquired and released @@ -1200,7 +1199,7 @@ static int move_swap_pte(struct mm_struct *mm, struct vm_area_struct *dst_vma, * cache, or during the tiny synchronization window between swap cache and * swap_map, but it will be gone very quickly, worst result is retry jitters. */ - if (READ_ONCE(si->swap_map[swp_offset(entry)]) & SWAP_HAS_CACHE) { + if (is_swap_cached(entry)) { double_pt_unlock(dst_ptl, src_ptl); return -EAGAIN; } -- 2.52.0