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 C8572C433DB for ; Tue, 26 Jan 2021 07:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 795FF207D0 for ; Tue, 26 Jan 2021 07:02:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389255AbhAZHCQ (ORCPT ); Tue, 26 Jan 2021 02:02:16 -0500 Received: from m42-8.mailgun.net ([69.72.42.8]:57729 "EHLO m42-8.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389325AbhAZG7z (ORCPT ); Tue, 26 Jan 2021 01:59:55 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1611644359; h=Message-Id: Date: Subject: Cc: To: From: Sender; bh=2/LGePk6+KJcWt28ddrE+6l1qc8VxrblsvOgqgDiP+U=; b=Zbi2+skGF0CH0tiREmFn7LD0gdSAElQzSoxkXpozWQK6oOviUJUs6MmrM27oZohm8r1TyJ0L TF8N9TrbgObAUaTBENn7L5IR8vX56T+eRWS7pR13LqRhd4KFKc96ZD7Kzrdx2liqhkazpKhy l06Rr5yWbr1ZD6izt5hh9E5iNe0= X-Mailgun-Sending-Ip: 69.72.42.8 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-n04.prod.us-west-2.postgun.com with SMTP id 600fbda1ad4c9e395bd0fe84 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 26 Jan 2021 06:58:41 GMT Sender: cgoldswo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 5F6D8C43465; Tue, 26 Jan 2021 06:58:41 +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 37E05C433C6; Tue, 26 Jan 2021 06:58:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 37E05C433C6 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: viro@zeniv.linux.org.uk Cc: Matthew Wilcox , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Goldsworthy Subject: [PATCH v4] Resolve LRU page-pinning issue for file-backed pages Date: Mon, 25 Jan 2021 22:58:29 -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. v4: Fix an iteration error. Laura Abbott (1): fs/buffer.c: Revoke LRU when trying to drop buffers fs/buffer.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 74 insertions(+), 5 deletions(-) -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project