From patchwork Thu Apr 17 21:10:53 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 14056185 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 7B46CC369C9 for ; Thu, 17 Apr 2025 21:11:39 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u5WW3-0005oG-AX; Thu, 17 Apr 2025 17:11:24 -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 1u5WVj-0005hI-Gt for qemu-devel@nongnu.org; Thu, 17 Apr 2025 17:11:04 -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 1u5WVg-00040e-Ps for qemu-devel@nongnu.org; Thu, 17 Apr 2025 17:11:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744924260; 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; bh=7pqbBncs4V+SEDkICJlqa8chCxJKrfcfYWPXIcEE80A=; b=FhqOBM5CWwzykoTR+afGcH4bGRfyhs0I9AV77z/RELid7y+0CiXUzREzqehnHHbQqHflnt aCXuomwnFP0dHs1/dJbcPyFJfmv5+rovz9pCZ75tgXzjdW0IkP2s9+F2mMCxOwvNCkIoBl qurxREJd8SPKeNzt9WuNGcz4Bs7Y83M= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-240-JzLR8leJO1GIfsAg5Gcygg-1; Thu, 17 Apr 2025 17:10:56 -0400 X-MC-Unique: JzLR8leJO1GIfsAg5Gcygg-1 X-Mimecast-MFC-AGG-ID: JzLR8leJO1GIfsAg5Gcygg_1744924255 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 93EAD1956094; Thu, 17 Apr 2025 21:10:55 +0000 (UTC) Received: from localhost (unknown [10.2.16.64]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id BAB591800D9E; Thu, 17 Apr 2025 21:10:54 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Hanna Reitz , Kevin Wolf , Stefan Hajnoczi , Paolo Bonzini , Christoph Hellwig Subject: [PATCH] block/file-posix: allow BLKZEROOUT with -t writeback Date: Thu, 17 Apr 2025 17:10:53 -0400 Message-ID: <20250417211053.98700-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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 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 --- block/file-posix.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 56d1972d15..9ba0b68958 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -781,17 +781,6 @@ 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)) { /*