From patchwork Tue Jan 5 07:05:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Goldsworthy X-Patchwork-Id: 11998227 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,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 46589C433E6 for ; Tue, 5 Jan 2021 07:07:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D02D22482 for ; Tue, 5 Jan 2021 07:07:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725971AbhAEHGz (ORCPT ); Tue, 5 Jan 2021 02:06:55 -0500 Received: from so254-31.mailgun.net ([198.61.254.31]:15684 "EHLO so254-31.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725710AbhAEHGy (ORCPT ); Tue, 5 Jan 2021 02:06:54 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1609830395; h=References: In-Reply-To: References: In-Reply-To: Message-Id: Date: Subject: Cc: To: From: Sender; bh=PSD4T8ASrr1pfYU48t/ftAURhWN9+rkwMmpAWedYLBE=; b=Gb/qk8dZYWERcy++PbwzGHx6gIOeNfvkFGNCaKyVjINS0C6niLYjr8XtcLi8pWeKQQSoYTnX EPipze5C6y4664txVDl9V2KdRgHlsP0cscB5zjEPhps+H7ZpYSk8PCmKoA4DMEo1w12FOTKk Cl8bcgmzrJv0qeA0jWiOCzQWYk0= 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-n07.prod.us-west-2.postgun.com with SMTP id 5ff40fcab73be0303d19c447 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 05 Jan 2021 07:05:46 GMT Sender: cgoldswo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 2F75DC43462; Tue, 5 Jan 2021 07:05:46 +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 89BFBC433C6; Tue, 5 Jan 2021 07:05:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 89BFBC433C6 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 , linux-fsdevel@vger.kernel.org, Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Laura Abbott , Chris Goldsworthy Subject: [PATCH v2] fs/buffer.c: Revoke LRU when trying to drop buffers Date: Mon, 4 Jan 2021 23:05:33 -0800 Message-Id: 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 Cc: Matthew Wilcox --- fs/buffer.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- fs/internal.h | 5 ++++ 2 files changed, 85 insertions(+), 5 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 96c7604..536fb5b 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -48,6 +48,7 @@ #include #include #include +#include #include "internal.h" @@ -1471,12 +1472,63 @@ static bool has_bh_in_lru(int cpu, void *dummy) return false; } +static void __evict_bhs_lru(void *arg) +{ + struct bh_lru *b = &get_cpu_var(bh_lrus); + struct busy_bhs_container *busy_bhs = arg; + struct buffer_head *bh; + int i; + + XA_STATE(xas, &busy_bhs->xarray, 0); + + xas_for_each(&xas, bh, busy_bhs->size) { + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i] == bh) { + brelse(b->bhs[i]); + b->bhs[i] = NULL; + break; + } + } + + bh = bh->b_this_page; + } + + put_cpu_var(bh_lrus); +} + +static bool page_has_bhs_in_lru(int cpu, void *arg) +{ + struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); + struct busy_bhs_container *busy_bhs = arg; + struct buffer_head *bh; + int i; + + XA_STATE(xas, &busy_bhs->xarray, 0); + + xas_for_each(&xas, bh, busy_bhs->size) { + for (i = 0; i < BH_LRU_SIZE; i++) { + if (b->bhs[i] == bh) + return true; + } + + bh = bh->b_this_page; + } + + 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 busy_bhs_container *busy_bhs) +{ + on_each_cpu_cond(page_has_bhs_in_lru, __evict_bhs_lru, + busy_bhs, 1); +} + void set_bh_page(struct buffer_head *bh, struct page *page, unsigned long offset) { @@ -3242,14 +3294,36 @@ drop_buffers(struct page *page, struct buffer_head **buffers_to_free) { struct buffer_head *head = page_buffers(page); struct buffer_head *bh; + struct busy_bhs_container busy_bhs; + int xa_ret, ret = 0; + + xa_init(&busy_bhs.xarray); + busy_bhs.size = 0; bh = head; do { - if (buffer_busy(bh)) - goto failed; + if (buffer_busy(bh)) { + xa_ret = xa_err(xa_store(&busy_bhs.xarray, busy_bhs.size++, + bh, GFP_ATOMIC)); + if (xa_ret) + goto out; + } bh = bh->b_this_page; } while (bh != head); + if (busy_bhs.size) { + /* + * Check if the busy failure was due to an outstanding + * LRU reference + */ + evict_bh_lrus(&busy_bhs); + do { + if (buffer_busy(bh)) + goto out; + } while (bh != head); + } + + ret = 1; do { struct buffer_head *next = bh->b_this_page; @@ -3259,9 +3333,10 @@ drop_buffers(struct page *page, struct buffer_head **buffers_to_free) } while (bh != head); *buffers_to_free = head; detach_page_private(page); - return 1; -failed: - return 0; +out: + xa_destroy(&busy_bhs.xarray); + + return ret; } int try_to_free_buffers(struct page *page) diff --git a/fs/internal.h b/fs/internal.h index 77c50be..00f17c4 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -15,6 +15,7 @@ struct mount; struct shrink_control; struct fs_context; struct user_namespace; +struct xarray; /* * block_dev.c @@ -49,6 +50,10 @@ static inline int emergency_thaw_bdev(struct super_block *sb) */ extern int __block_write_begin_int(struct page *page, loff_t pos, unsigned len, get_block_t *get_block, struct iomap *iomap); +struct busy_bhs_container { + struct xarray xarray; + int size; +}; /* * char_dev.c