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 X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73DAAC43333 for ; Thu, 14 Jan 2021 02:14:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E2A72242A for ; Thu, 14 Jan 2021 02:14:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729149AbhAMVbw (ORCPT ); Wed, 13 Jan 2021 16:31:52 -0500 Received: from so254-31.mailgun.net ([198.61.254.31]:13772 "EHLO so254-31.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729140AbhAMVaU (ORCPT ); Wed, 13 Jan 2021 16:30:20 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1610573400; h=Message-Id: Date: Subject: Cc: To: From: Sender; bh=Ch2XVgOCR5t+oWiqNZvTCBTunPhnsKohqMu9LnBESb0=; b=es2JS2pa9Hi5vc9VAIfmIMnCsXmzTaroiI2LioBvOCnxxJC1Wwa6WY4IsCDlibQt/j7kIp5a OiYtqP2iHDH+gp2OIlcnLEMnngLSuEsKqL13ACFhtNqdeJeBSW6ZxB55I3255bLpALztVhYS USu7BGepD97gRRJPjUCc4EMvMgc= X-Mailgun-Sending-Ip: 198.61.254.31 X-Mailgun-Sid: WyIxOTQxNiIsICJsaW51eC1mc2RldmVsQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-east-1.postgun.com with SMTP id 5fff63708fb3cda82fb0335c (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Wed, 13 Jan 2021 21:17:36 GMT Sender: cgoldswo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id CB0F4C43463; Wed, 13 Jan 2021 21:17:35 +0000 (UTC) Received: from cgoldswo-linux.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: cgoldswo) by smtp.codeaurora.org (Postfix) with ESMTPSA id D71CAC433CA; Wed, 13 Jan 2021 21:17:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org D71CAC433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=cgoldswo@codeaurora.org From: Chris Goldsworthy To: Alexander Viro Cc: Matthew Wilcox , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Goldsworthy Subject: [PATCH v3] Resolve LRU page-pinning issue for file-backed pages Date: Wed, 13 Jan 2021 13:17:29 -0800 Message-Id: X-Mailer: git-send-email 2.7.4 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org It is possible for file-backed pages to end up in a contiguous memory area (CMA), such that the relevant page must be migrated using the .migratepage() callback when its backing physical memory is selected for use in an CMA allocation (through cma_alloc()). However, if a set of address space operations (AOPs) for a file-backed page lacks a migratepage() page call-back, fallback_migrate_page() will be used instead, which through try_to_release_page() calls try_to_free_buffers() (which is called directly or through a try_to_free_buffers() callback. try_to_free_buffers() in turn calls drop_buffers() drop_buffers() itself can fail due to the buffer_head associated with a page being busy. However, it is possible that the buffer_head is on an LRU list for a CPU, such that we can try removing the buffer_head from that list, in order to successfully release the page. Do this. v1: https://lore.kernel.org/lkml/cover.1606194703.git.cgoldswo@codeaurora.org/T/#m3a44b5745054206665455625ccaf27379df8a190 Original version of the patch (with updates to make to account for changes in on_each_cpu_cond()). v2: https://lore.kernel.org/lkml/cover.1609829465.git.cgoldswo@codeaurora.org/ Follow Matthew Wilcox's suggestion of reducing the number of calls to on_each_cpu_cond(), by iterating over a page's busy buffer_heads inside of on_each_cpu_cond(). To copy from his e-mail, we go from: for_each_buffer for_each_cpu for_each_lru_entry to: for_each_cpu for_each_buffer for_each_lru_entry This is done using xarrays, which I found to be the cleanest data structure to use, though a pre-allocated array of page_size(page) / bh->b_size elements might be more performant. v3: Replace xas_for_each() with xa_for_each() to account for proper locking. Laura Abbott (1): fs/buffer.c: Revoke LRU when trying to drop buffers fs/buffer.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 76 insertions(+), 5 deletions(-) -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project