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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 758EBC83F03 for ; Fri, 4 Jul 2025 18:18:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 11CDD6B8062; Fri, 4 Jul 2025 14:18:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0CDC56B8059; Fri, 4 Jul 2025 14:18:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EFFBD6B8062; Fri, 4 Jul 2025 14:18:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id DB9706B8059 for ; Fri, 4 Jul 2025 14:18:20 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 5A392124E46 for ; Fri, 4 Jul 2025 18:18:20 +0000 (UTC) X-FDA: 83627391960.17.E817AA2 Received: from mail-qk1-f172.google.com (mail-qk1-f172.google.com [209.85.222.172]) by imf09.hostedemail.com (Postfix) with ESMTP id 750F2140005 for ; Fri, 4 Jul 2025 18:18:18 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=f6YriDfK; spf=pass (imf09.hostedemail.com: domain of ryncsn@gmail.com designates 209.85.222.172 as permitted sender) smtp.mailfrom=ryncsn@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=1751653098; h=from:from:sender:reply-to: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=XZoMdOAYvbZ00cTZOCHcf1+vcwk6yO09XTz7UlT/lic=; b=5Aj9YJw9jltIXRwIomM8MncohX+ay5bQKodZw05DJiiTFQF2zyb90U7nnwb7r8NDXDGZrG 4Ar6saWfJD+FNFgQAGuYi/wjgFR1cv+xdPfAmaA+CYcHLgEy6+hKCbef5CZj446uyO4WC0 GeDJbF2ERJtK7nNHvOazBsKOOqXy6rA= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=f6YriDfK; spf=pass (imf09.hostedemail.com: domain of ryncsn@gmail.com designates 209.85.222.172 as permitted sender) smtp.mailfrom=ryncsn@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1751653098; a=rsa-sha256; cv=none; b=BNTxRx3a6J/gETPcolUnuKaWyQ40QoF+9lYuIuS1+f9RfdTPMYWrlgPJbU+2lWEHsSXZGX N7gd63kNo95Ylta0HtY67dR9QoHLxGdKTO33LXV2j5gOwrB5bptlzT8FiwpHx2fWg1ha6A hZqoCEMK3nTy3mgK02xUHr/WtpkfYJ4= Received: by mail-qk1-f172.google.com with SMTP id af79cd13be357-7d094ef02e5so308067785a.1 for ; Fri, 04 Jul 2025 11:18:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1751653097; x=1752257897; darn=kvack.org; h=content-transfer-encoding:mime-version:reply-to:references :in-reply-to:message-id:date:subject:cc:to:from:from:to:cc:subject :date:message-id:reply-to; bh=XZoMdOAYvbZ00cTZOCHcf1+vcwk6yO09XTz7UlT/lic=; b=f6YriDfKHA1ewY2A3geOcYkuHm4G8A1f9g71d34ymtjIxeqPc3Yn07jVkkV/d26zO1 4InOYtMkRMye8sGOqJyovYN95F4QzjGlzUEgPL3noMz8S2Mc0aKaHQQWAW/2Nc1CovNU iBCqQ1l4jqgrkkK/8GBfVkBOZtv/zFbTcQHjX22e/kQD8VNFwXSFuHXQyBr2F2HVThLz DZmM9xDXNwTWnwUzG/tpU8iPN08UIbkJ4wSmqsu4h1nt+Wf3wQ8i6Egow2IYTF1ppTCb +PSxlqlUGCVgvQ+cvs0LkPTzVYh445MGQhzpYGKPfU8/6Dxaij2kyrnHQvEN5/+3UXlK 3hUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751653097; x=1752257897; h=content-transfer-encoding:mime-version:reply-to:references :in-reply-to:message-id:date:subject:cc:to:from:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=XZoMdOAYvbZ00cTZOCHcf1+vcwk6yO09XTz7UlT/lic=; b=IswhtsGSSe7Vo7qDt/7SQnQBv0FW19fBJUUJP5HU8cg28JotiEvGOHorjD7f2lR/wh v02tKQIfllf7GD++BSB+O5ZfjbqcqLGYuORPe/3DCkIW+Bev//TDQtTf5usjbmkw+qVC Cd4+OrJFZLpQ7GSaXkQLDV2k+koIl3G1ckcE2Q+XYgbUW7MyJavAnXZSaEts7Wq94IK/ stkhCYvGfpjAWanUl55E8yPix3LnKQufe2AV4j/pp/w8DKZ643E1D+bTCtEXgo9ZA5m/ r8dBxRKenWIq308xXb+PaIETjkK3Hu2m07iNR4oGtEKnhTvfYsvR5z/0JE74GSLdbYdB /EXA== X-Gm-Message-State: AOJu0YwGgVlzNXdNTfhpMzuIATIYbFajU6EUMpjz8TGFPq95wG4ZN44A rL/QM9mJx2gO9A092fS9ypIKOvjkR+VisSjGiYszf3WYGVPHLIEszw0HRCK18kB5ggA= X-Gm-Gg: ASbGncun0CXVGJG9bQvQOuWMNWMyshcZxxou9fxSVLhYSHO7DKydrEjgsJsNPCyQfZr MOu7qOLPQDMF3D7YgEldeB12vLppdFOrCu5Clq4k4U8HSCVDGVvD22TcIzkq0g8ijL/IyBOwDiq WL1IuNQMmD236gmhtg32OBxmQY0ckI6Wpwirrj8rxgkKv+Ka3EgJhvOBrPWHCn1tgpWnlovvnVI wPjD7kRZduwDRh6FeEWabDFMeBoyIg3UQ0i62qsfm8Fi0sEAltlMngfriwIHpkC6p3k6LvlnnUb WYtVKVFsuXTBLYI0UK3UozXbMJvsgCcfYEFtgvAdGbCF1zhfn6BGSO217IdNnY0nALg= X-Google-Smtp-Source: AGHT+IHZ2nb6ar//pNiW7UrB4lVG4pdlvO/xT2T5TEyaxDBNRUFLNVCBYd9MeBTl7yyXqu9f+E/xqw== X-Received: by 2002:a05:620a:2982:b0:7d4:67f1:df8d with SMTP id af79cd13be357-7d5dcd2e0dcmr605505985a.21.1751653096350; Fri, 04 Jul 2025 11:18:16 -0700 (PDT) Received: from KASONG-MC4 ([101.32.222.185]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7d5dbe7c188sm183300585a.59.2025.07.04.11.18.12 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 04 Jul 2025 11:18:15 -0700 (PDT) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Hugh Dickins , Baolin Wang , Matthew Wilcox , Kemeng Shi , Chris Li , Nhat Pham , Baoquan He , Barry Song , linux-kernel@vger.kernel.org, Kairui Song Subject: [PATCH v4 4/9] mm/shmem, swap: tidy up swap entry splitting Date: Sat, 5 Jul 2025 02:17:43 +0800 Message-ID: <20250704181748.63181-5-ryncsn@gmail.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250704181748.63181-1-ryncsn@gmail.com> References: <20250704181748.63181-1-ryncsn@gmail.com> Reply-To: Kairui Song MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: per76tuwywuco684fpeyub9iaf1wwxsd X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 750F2140005 X-HE-Tag: 1751653098-709076 X-HE-Meta: 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 mAxJqm6h 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Kairui Song Instead of keeping different paths of splitting the entry before the swap in start, move the entry splitting after the swapin has put the folio in swap cache (or set the SWAP_HAS_CACHE bit). This way we only need one place and one unified way to split the large entry. Whenever swapin brought in a folio smaller than the shmem swap entry, split the entry and recalculate the entry and index for verification. This removes duplicated codes and function calls, reduces LOC, and the split is less racy as it's guarded by swap cache now. So it will have a lower chance of repeated faults due to raced split. The compiler is also able to optimize the coder further: bloat-o-meter results with GCC 14: With DEBUG_SECTION_MISMATCH (-fno-inline-functions-called-once): ./scripts/bloat-o-meter mm/shmem.o.old mm/shmem.o add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-82 (-82) Function old new delta shmem_swapin_folio 2361 2279 -82 Total: Before=33151, After=33069, chg -0.25% With !DEBUG_SECTION_MISMATCH: ./scripts/bloat-o-meter mm/shmem.o.old mm/shmem.o add/remove: 0/1 grow/shrink: 1/0 up/down: 949/-750 (199) Function old new delta shmem_swapin_folio 2878 3827 +949 shmem_split_large_entry.isra 750 - -750 Total: Before=33086, After=33285, chg +0.60% Since shmem_split_large_entry is only called in one place now. The compiler will either generate more compact code, or inlined it for better performance. Signed-off-by: Kairui Song --- mm/shmem.c | 53 +++++++++++++++++++++-------------------------------- 1 file changed, 21 insertions(+), 32 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index e43becfa04b3..217264315842 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2266,14 +2266,15 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, struct address_space *mapping = inode->i_mapping; struct mm_struct *fault_mm = vma ? vma->vm_mm : NULL; struct shmem_inode_info *info = SHMEM_I(inode); + swp_entry_t swap, index_entry; struct swap_info_struct *si; struct folio *folio = NULL; bool skip_swapcache = false; - swp_entry_t swap; int error, nr_pages, order, split_order; + pgoff_t offset; VM_BUG_ON(!*foliop || !xa_is_value(*foliop)); - swap = radix_to_swp_entry(*foliop); + swap = index_entry = radix_to_swp_entry(*foliop); *foliop = NULL; if (is_poisoned_swp_entry(swap)) @@ -2321,46 +2322,35 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, } /* - * Now swap device can only swap in order 0 folio, then we - * should split the large swap entry stored in the pagecache - * if necessary. - */ - split_order = shmem_split_large_entry(inode, index, swap, gfp); - if (split_order < 0) { - error = split_order; - goto failed; - } - - /* - * If the large swap entry has already been split, it is + * Now swap device can only swap in order 0 folio, it is * necessary to recalculate the new swap entry based on - * the old order alignment. + * the offset, as the swapin index might be unalgined. */ - if (split_order > 0) { - pgoff_t offset = index - round_down(index, 1 << split_order); - + if (order) { + offset = index - round_down(index, 1 << order); swap = swp_entry(swp_type(swap), swp_offset(swap) + offset); } - /* Here we actually start the io */ folio = shmem_swapin_cluster(swap, gfp, info, index); if (!folio) { error = -ENOMEM; goto failed; } - } else if (order > folio_order(folio)) { + } +alloced: + if (order > folio_order(folio)) { /* - * Swap readahead may swap in order 0 folios into swapcache + * Swapin may get smaller folios due to various reasons: + * It may fallback to order 0 due to memory pressure or race, + * swap readahead may swap in order 0 folios into swapcache * asynchronously, while the shmem mapping can still stores * large swap entries. In such cases, we should split the * large swap entry to prevent possible data corruption. */ - split_order = shmem_split_large_entry(inode, index, swap, gfp); + split_order = shmem_split_large_entry(inode, index, index_entry, gfp); if (split_order < 0) { - folio_put(folio); - folio = NULL; error = split_order; - goto failed; + goto failed_nolock; } /* @@ -2369,15 +2359,13 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, * the old order alignment. */ if (split_order > 0) { - pgoff_t offset = index - round_down(index, 1 << split_order); - + offset = index - round_down(index, 1 << split_order); swap = swp_entry(swp_type(swap), swp_offset(swap) + offset); } } else if (order < folio_order(folio)) { swap.val = round_down(swap.val, 1 << folio_order(folio)); } -alloced: /* We have to do this with folio locked to prevent races */ folio_lock(folio); if ((!skip_swapcache && !folio_test_swapcache(folio)) || @@ -2434,12 +2422,13 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index, shmem_set_folio_swapin_error(inode, index, folio, swap, skip_swapcache); unlock: - if (skip_swapcache) - swapcache_clear(si, swap, folio_nr_pages(folio)); - if (folio) { + if (folio) folio_unlock(folio); +failed_nolock: + if (skip_swapcache) + swapcache_clear(si, folio->swap, folio_nr_pages(folio)); + if (folio) folio_put(folio); - } put_swap_device(si); return error; } -- 2.50.0