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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ABFBDC54ED0 for ; Thu, 22 May 2025 18:32:36 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uIAhz-0005oT-Vi; Thu, 22 May 2025 14:32:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uIAhf-0005nA-5t for qemu-devel@nongnu.org; Thu, 22 May 2025 14:31:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uIAhX-0000OI-WC for qemu-devel@nongnu.org; Thu, 22 May 2025 14:31:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747938691; h=from:from:reply-to:subject:subject: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=EoG2vVF1mLkEop2GmLcTYDfoevSG58BUGG0ufuqbsyE=; b=dU/1U5h8QpiwMrt5lc4HqYnyBScxKTUVWiK4PETMgyRgTykBMzDPnz0PXiiFYsT8DU88+n CBvUjkhj32uWbQad+CvdNC5rGFrLPYUfJDwiYW7qLyzs/TFJrmkZ5kAi7I2LrOi+vhkmOS xfAOsvuWgDOJR8VxkiZcOah9hVCTAf8= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-596-2gpnAbIzNp6LiGBWBt2ggQ-1; Thu, 22 May 2025 14:31:27 -0400 X-MC-Unique: 2gpnAbIzNp6LiGBWBt2ggQ-1 X-Mimecast-MFC-AGG-ID: 2gpnAbIzNp6LiGBWBt2ggQ_1747938686 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D147F180036F; Thu, 22 May 2025 18:31:26 +0000 (UTC) Received: from merkur.redhat.com (unknown [10.45.226.76]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8DE0D1944DFF; Thu, 22 May 2025 18:31:25 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 4/5] file-posix: allow BLKZEROOUT with -t writeback Date: Thu, 22 May 2025 20:31:14 +0200 Message-ID: <20250522183115.246746-5-kwolf@redhat.com> In-Reply-To: <20250522183115.246746-1-kwolf@redhat.com> References: <20250522183115.246746-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.275, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Stefan Hajnoczi The Linux BLKZEROOUT ioctl is only invoked when BDRV_O_NOCACHE is set because old kernels did not invalidate the page cache. In that case mixing BLKZEROOUT with buffered I/O could lead to corruption. However, Linux 4.9 commit 22dd6d356628 ("block: invalidate the page cache when issuing BLKZEROOUT") made BLKZEROOUT coherent with the page cache. I have checked that Linux 4.9+ kernels are shipped at least as far back as Debian 10 (buster), openSUSE Leap 15.2, and RHEL/CentOS 8. Use BLKZEROOUT with buffered I/O, mostly so `qemu-img ... -t writeback` can offload write zeroes. Cc: Paolo Bonzini Cc: Christoph Hellwig Signed-off-by: Stefan Hajnoczi Message-ID: <20250417211053.98700-1-stefanha@redhat.com> Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/file-posix.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index ec95b74869..5a3532e40b 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -785,17 +785,6 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } #endif - if (S_ISBLK(st.st_mode)) { -#ifdef __linux__ - /* On Linux 3.10, BLKDISCARD leaves stale data in the page cache. Do - * not rely on the contents of discarded blocks unless using O_DIRECT. - * Same for BLKZEROOUT. - */ - if (!(bs->open_flags & BDRV_O_NOCACHE)) { - s->has_write_zeroes = false; - } -#endif - } #ifdef __FreeBSD__ if (S_ISCHR(st.st_mode)) { /* -- 2.49.0