From patchwork Fri Feb 11 09:46:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Zimmermann X-Patchwork-Id: 12743111 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 F359EC433EF for ; Fri, 11 Feb 2022 09:46:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242819AbiBKJqp (ORCPT ); Fri, 11 Feb 2022 04:46:45 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:33104 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343993AbiBKJqo (ORCPT ); Fri, 11 Feb 2022 04:46:44 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F08E10A2 for ; Fri, 11 Feb 2022 01:46:44 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id B9D361F3A2; Fri, 11 Feb 2022 09:46:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1644572802; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Rr/O6TIKP8Y1rYJpt7Gr1aalvRe+WTfBbdZrMfRKh5o=; b=MrepO+7/J+2mJI0T7QTZ4QrH60NDHNZ0Dx2IjZ5wMz/7YyN2lNsxHlzWyLzSSdII6R1iAF wU7U5Q1OmPpGR5Y7yVhf/gCmzn8JvIpo71R1XsfZbNgr2LlMyzWoQWbil7r5r0NaO8aTCe nxGJ7M9FnUs/KmmYjm/x7Pl2pO+HKnE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1644572802; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Rr/O6TIKP8Y1rYJpt7Gr1aalvRe+WTfBbdZrMfRKh5o=; b=2YHAfBmv3pK1Za/cI43eXpKM9GF+XUowzoq7OyvzGqGR0/1TKKUrAjaTlbJj9vkV8MR6h5 dVNODF+xg9MqDhDA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 7611513BDD; Fri, 11 Feb 2022 09:46:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 2ADPG4IwBmKMHQAAMHmgww (envelope-from ); Fri, 11 Feb 2022 09:46:42 +0000 From: Thomas Zimmermann To: daniel@ffwll.ch, javierm@redhat.com, noralf@tronnes.org, andriy.shevchenko@linux.intel.com, deller@gmx.de, bernie@plugable.com, jayalk@intworks.biz Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-staging@lists.linux.dev, Thomas Zimmermann , Sam Ravnborg Subject: [PATCH v2 1/2] fbdev/defio: Early-out if page is already enlisted Date: Fri, 11 Feb 2022 10:46:39 +0100 Message-Id: <20220211094640.21632-2-tzimmermann@suse.de> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220211094640.21632-1-tzimmermann@suse.de> References: <20220211094640.21632-1-tzimmermann@suse.de> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Return early if a page is already in the list of dirty pages for deferred I/O. This can be detected if the page's list head is not empty. Keep the list head initialized while the page is not enlisted to make this work reliably. v2: * update comment and fix spelling (Sam) Signed-off-by: Thomas Zimmermann Acked-by: Sam Ravnborg --- drivers/video/fbdev/core/fb_defio.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index a591d291b231..169a81c8172b 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -59,6 +59,7 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf) printk(KERN_ERR "no mapping available\n"); BUG_ON(!page->mapping); + INIT_LIST_HEAD(&page->lru); page->index = vmf->pgoff; vmf->page = page; @@ -122,17 +123,24 @@ static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf) */ lock_page(page); + /* + * This check is to catch the case where a new process could start + * writing to the same page through a new PTE. This new access + * can cause a call to .page_mkwrite even if the original process' + * PTE is marked writable. + * + * TODO: The lru field is owned by the page cache; hence the name. + * We dequeue in fb_deferred_io_work() after flushing the + * page's content into video memory. Instead of lru, fbdefio + * should have it's own field. + */ + if (!list_empty(&page->lru)) + goto page_already_added; + /* we loop through the pagelist before adding in order to keep the pagelist sorted */ list_for_each_entry(cur, &fbdefio->pagelist, lru) { - /* this check is to catch the case where a new - process could start writing to the same page - through a new pte. this new access can cause the - mkwrite even when the original ps's pte is marked - writable */ - if (unlikely(cur == page)) - goto page_already_added; - else if (cur->index > page->index) + if (cur->index > page->index) break; } @@ -194,7 +202,7 @@ static void fb_deferred_io_work(struct work_struct *work) /* clear the list */ list_for_each_safe(node, next, &fbdefio->pagelist) { - list_del(node); + list_del_init(node); } mutex_unlock(&fbdefio->lock); }