From patchwork Tue Nov 24 06:49:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Goldsworthy X-Patchwork-Id: 11927291 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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 7EE4EC63798 for ; Tue, 24 Nov 2020 06:49:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1352F206FA for ; Tue, 24 Nov 2020 06:49:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="W4kM7fyk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729862AbgKXGtu (ORCPT ); Tue, 24 Nov 2020 01:49:50 -0500 Received: from m42-4.mailgun.net ([69.72.42.4]:45374 "EHLO m42-4.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729856AbgKXGtu (ORCPT ); Tue, 24 Nov 2020 01:49:50 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1606200589; h=References: In-Reply-To: References: In-Reply-To: Message-Id: Date: Subject: Cc: To: From: Sender; bh=UDO+Y8s0zbY40OPyGLj6G8krTvl3bn+bwk439waak+c=; b=W4kM7fykYA8KS2VSxiKtwCM3oRyKZKh9Bmkk3iDJd7xuZvwgWr4C6uoJpKA1Qa2XHu114G1q 7oC+bbZWc1eqj6l28I/UyyMlAtUE/qMqPhYhKl0gubryoizk/6+pZ+QhEgxVFnMSGAYThHZQ 7c94ASp0KVkrN/tzixRL06eYGMc= X-Mailgun-Sending-Ip: 69.72.42.4 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 5fbcad0d1b731a5d9c07b84f (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 24 Nov 2020 06:49:49 GMT Sender: cgoldswo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 2C2DBC43463; Tue, 24 Nov 2020 06:49:48 +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 4DEE4C43460; Tue, 24 Nov 2020 06:49:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 4DEE4C43460 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: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, david@redhat.com, Laura Abbott , Chris Goldsworthy Subject: [PATCH] fs/buffer.c: Revoke LRU when trying to drop buffers Date: Mon, 23 Nov 2020 22:49:38 -0800 Message-Id: <1fe5d53722407a2651eeeada3a422c117041bf1d.1606194703.git.cgoldswo@codeaurora.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Laura Abbott When a buffer is added to the LRU list, a reference is taken which is not dropped until the buffer is evicted from the LRU list. This is the correct behavior, however this LRU reference will prevent the buffer from being dropped. This means that the buffer can't actually be dropped until it is selected for eviction. There's no bound on the time spent on the LRU list, which means that the buffer may be undroppable for very long periods of time. Given that migration involves dropping buffers, the associated page is now unmigratible for long periods of time as well. CMA relies on being able to migrate a specific range of pages, so these types of failures make CMA significantly less reliable, especially under high filesystem usage. Rather than waiting for the LRU algorithm to eventually kick out the buffer, explicitly remove the buffer from the LRU list when trying to drop it. There is still the possibility that the buffer could be added back on the list, but that indicates the buffer is still in use and would probably have other 'in use' indicates to prevent dropping. Signed-off-by: Laura Abbott Signed-off-by: Chris Goldsworthy --- fs/buffer.c | 47 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 45 insertions(+), 2 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 64564ac..1751f0b 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1471,12 +1471,48 @@ static bool has_bh_in_lru(int cpu, void *dummy) return false; } +static void __evict_bh_lru(void *arg) +{ + struct bh_lru *b = &get_cpu_var(bh_lrus); + struct buffer_head *bh = arg; + int i; + + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i] == bh) { + brelse(b->bhs[i]); + b->bhs[i] = NULL; + goto out; + } + } +out: + put_cpu_var(bh_lrus); +} + +static bool bh_exists_in_lru(int cpu, void *arg) +{ + struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); + struct buffer_head *bh = arg; + int i; + + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i] == bh) + return true; + } + + return false; + +} void invalidate_bh_lrus(void) { on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1); } EXPORT_SYMBOL_GPL(invalidate_bh_lrus); +static void evict_bh_lrus(struct buffer_head *bh) +{ + on_each_cpu_cond(bh_exists_in_lru, __evict_bh_lru, bh, 1); +} + void set_bh_page(struct buffer_head *bh, struct page *page, unsigned long offset) { @@ -3245,8 +3281,15 @@ drop_buffers(struct page *page, struct buffer_head **buffers_to_free) bh = head; do { - if (buffer_busy(bh)) - goto failed; + if (buffer_busy(bh)) { + /* + * Check if the busy failure was due to an + * outstanding LRU reference + */ + evict_bh_lrus(bh); + if (buffer_busy(bh)) + goto failed; + } bh = bh->b_this_page; } while (bh != head);