From patchwork Tue Feb 7 02:52:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Chamberlain X-Patchwork-Id: 53615 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp2608891wrn; Mon, 6 Feb 2023 18:56:07 -0800 (PST) X-Google-Smtp-Source: AK7set/JV+TQrei2RaWtWtbfTHeSyISQ9aCw6/3gom/jgzDNTEqMydEw19BBBuKss82b36UbOdCp X-Received: by 2002:a17:90b:3a8b:b0:230:9b7b:20fd with SMTP id om11-20020a17090b3a8b00b002309b7b20fdmr2306537pjb.5.1675738567539; Mon, 06 Feb 2023 18:56:07 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1675738567; cv=none; d=google.com; s=arc-20160816; b=Xp40Y6kOGcZFmK4t5FAl0kA2K8ZhM2o23lylqGKx6K4jEHmawvz6Exlbh/QDsTG7FX YbACE8XbATAuTGwNn3tjA1Nf8zHAL0uv426FKAmwKdaen+HJRcicvXHIGN+5rnTGN8TQ +E70mE0gpkwoJCtMkEJofrVrOBHUCs9uozCGxDbSzk4UNC5oUJ6tFYN7Qm/YSD19Kxqb memBx2n5buiYgJBpsGGnB/XO9Z51H92CJa62T8MZg/LM4XtDeoHDBnqFObqYo2ku9m5J 85MEOR7zJAeC9bkzVM7wa+IX4AxjlIMM5ipH6nDOEXyT5KMfPKTQakst9vqro3cVY2uN ZXzg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=ppc+iA/4jLT/kyK/2EkWiSyEAfiza0foS2nW0M1ktaU=; b=hop5owPLCDAF4sUR5Ebo07YSwNU5NMhllB7NKGQPOscCjyqaoZGUVhlabyAyxyyKL6 0MbsOoBua11gtfk2NzTDVcT3D+PFoGJtuBUfLZVQryUdwyqqj+La4zA9YWvBWmjhOt4C Gu4ZKgsASiM4ryM7O28TjVNRua0PxO1bZ7+En2FPDg1wOJGJ1Jjp2EjGAJWo4sFBhtHV 3avMjijmxa4yU/hzT6asozRaBwHNO6UT45Vt5LV9aTiUTf9Avh2atUf9Bkb6ourGBnkY S074WXL+bnpz29TtjAvktPSvY0giXVbzEIWkQbz545u7pDpy+3Sbw2N7gOIrbCm1NPwA Yvxg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20210309 header.b=Hyly4Ctg; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id g15-20020a63b14f000000b00476e640ddfesi13344961pgp.80.2023.02.06.18.55.54; Mon, 06 Feb 2023 18:56:07 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20210309 header.b=Hyly4Ctg; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229954AbjBGCxO (ORCPT + 99 others); Mon, 6 Feb 2023 21:53:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229781AbjBGCxM (ORCPT ); Mon, 6 Feb 2023 21:53:12 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D59D5468B for ; Mon, 6 Feb 2023 18:53:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=ppc+iA/4jLT/kyK/2EkWiSyEAfiza0foS2nW0M1ktaU=; b=Hyly4Ctgcl2ybcZ9Uf6YVJBbZj d8rXp8MTOtkLsYo89C6303qGny+ZLJ8X1/OlyBMSZJiK5eMMDXxjvBmjonKGnjQ60/1hfMX6pbfg8 yiKR4m6fBQf9AmmC/PJ3Sfm6BxquDZdjRcVWMEhdS6CAi2O3XaUWdAA1WK4305EBn7wctnsiPwLLc HlI1EXwYA1U1BLrsam0jMtbVPygKbeNK0X1ap6NHxElHw5Vshw6660O0DRiXF2lpD7cUTvkaqNDg+ fFL17wN/1bPIrceXZHl+j0O+JrhHxGb7P5oTJxapL85uPnZY8Kw3vxY2kKsojLU/jZ8kPUpN88pMo SMb57LLQ==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pPE6S-00AaIb-SN; Tue, 07 Feb 2023 02:53:04 +0000 From: Luis Chamberlain To: hughd@google.com, akpm@linux-foundation.org, willy@infradead.org Cc: linux-mm@kvack.org, p.raghav@samsung.com, dave@stgolabs.net, a.manzanares@samsung.com, linux-kernel@vger.kernel.org, Luis Chamberlain Subject: [RFC 1/2] shmem: set shmem_writepage() variables early Date: Mon, 6 Feb 2023 18:52:58 -0800 Message-Id: <20230207025259.2522793-2-mcgrof@kernel.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20230207025259.2522793-1-mcgrof@kernel.org> References: <20230207025259.2522793-1-mcgrof@kernel.org> MIME-Version: 1.0 Sender: Luis Chamberlain X-Spam-Status: No, score=-4.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1757139243874604281?= X-GMAIL-MSGID: =?utf-8?q?1757139243874604281?= shmem_writepage() sets up variables typically used *after* a possible huge page split. However even if that does happen the address space mapping should not change. So it should be safe to set that from the beginning. The folio should always be locked from the start as well. It however was not clear if the folio address can / should change, as well as the first inode. This commit makes no functional changes other a double check on the folio locking which might be superflous. This change should help make the subsequent patch easier to review. Signed-off-by: Luis Chamberlain --- mm/shmem.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 28f3c699c8ce..a2c6aa11aab8 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1332,11 +1332,13 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) { struct folio *folio = page_folio(page); struct shmem_inode_info *info; - struct address_space *mapping; - struct inode *inode; + struct address_space *mapping = folio->mapping; + struct inode *inode = mapping->host; swp_entry_t swap; pgoff_t index; + BUG_ON(!folio_test_locked(folio)); + /* * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages, @@ -1351,8 +1353,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) folio_clear_dirty(folio); } + /* Can the folio or first inode change on after a split? */ BUG_ON(!folio_test_locked(folio)); - mapping = folio->mapping; index = folio->index; inode = mapping->host; info = SHMEM_I(inode);