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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D623ECAAD5 for ; Tue, 6 Sep 2022 14:22:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241516AbiIFOWg (ORCPT ); Tue, 6 Sep 2022 10:22:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241541AbiIFOUh (ORCPT ); Tue, 6 Sep 2022 10:20:37 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 509048E0D2; Tue, 6 Sep 2022 06:52:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 201CDB818B9; Tue, 6 Sep 2022 13:43:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75008C433B5; Tue, 6 Sep 2022 13:43:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662471804; bh=qYj6QWQQFcsSmu0dE62oXSFsUmz/XNnl8T4thWZSX88=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BL3SnSqD4kk//AWPj//O+8EogBCKlMHIVW+BteSsUWIeJl+7NUBNSRmG7irh7WUug yRhyLMX6OCrUqwGW8zsZymqXIDHHW5bhhZ8FTzK04sLdKfojchIOpGi+xJv3TdJovQ FV+qLu+48C7WrguoBcpcRXDFgbTDBg3Rvb/rm2DY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Yongqing Li , Xin Yin , David Howells , Jeffle Xu , Gao Xiang , Sasha Levin Subject: [PATCH 5.19 045/155] cachefiles: make on-demand request distribution fairer Date: Tue, 6 Sep 2022 15:29:53 +0200 Message-Id: <20220906132831.315405017@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220906132829.417117002@linuxfoundation.org> References: <20220906132829.417117002@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Xin Yin [ Upstream commit 1122f40072731525c06b1371cfa30112b9b54d27 ] For now, enqueuing and dequeuing on-demand requests all start from idx 0, this makes request distribution unfair. In the weighty concurrent I/O scenario, the request stored in higher idx will starve. Searching requests cyclically in cachefiles_ondemand_daemon_read, makes distribution fairer. Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie") Reported-by: Yongqing Li Signed-off-by: Xin Yin Signed-off-by: David Howells Reviewed-by: Jeffle Xu Reviewed-by: Gao Xiang Link: https://lore.kernel.org/r/20220817065200.11543-1-yinxin.x@bytedance.com/ # v1 Link: https://lore.kernel.org/r/20220825020945.2293-1-yinxin.x@bytedance.com/ # v2 Signed-off-by: Sasha Levin --- fs/cachefiles/internal.h | 1 + fs/cachefiles/ondemand.c | 12 +++++++++--- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index 6cba2c6de2f96..2ad58c4652084 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -111,6 +111,7 @@ struct cachefiles_cache { char *tag; /* cache binding tag */ refcount_t unbind_pincount;/* refcount to do daemon unbind */ struct xarray reqs; /* xarray of pending on-demand requests */ + unsigned long req_id_next; struct xarray ondemand_ids; /* xarray for ondemand_id allocation */ u32 ondemand_id_next; }; diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 7e1586bd5cf34..0254ed39f68ce 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -242,14 +242,19 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, unsigned long id = 0; size_t n; int ret = 0; - XA_STATE(xas, &cache->reqs, 0); + XA_STATE(xas, &cache->reqs, cache->req_id_next); /* - * Search for a request that has not ever been processed, to prevent - * requests from being processed repeatedly. + * Cyclically search for a request that has not ever been processed, + * to prevent requests from being processed repeatedly, and make + * request distribution fair. */ xa_lock(&cache->reqs); req = xas_find_marked(&xas, UINT_MAX, CACHEFILES_REQ_NEW); + if (!req && cache->req_id_next > 0) { + xas_set(&xas, 0); + req = xas_find_marked(&xas, cache->req_id_next - 1, CACHEFILES_REQ_NEW); + } if (!req) { xa_unlock(&cache->reqs); return 0; @@ -264,6 +269,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, } xas_clear_mark(&xas, CACHEFILES_REQ_NEW); + cache->req_id_next = xas.xa_index + 1; xa_unlock(&cache->reqs); id = xas.xa_index; -- 2.35.1