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 62E42CAC5B8 for ; Thu, 2 Oct 2025 19:40:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v4P7s-0007Lj-8z; Thu, 02 Oct 2025 15:38:04 -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 1v4P7g-0007Hl-VH for qemu-devel@nongnu.org; Thu, 02 Oct 2025 15:37:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v4P7W-0000Wf-23 for qemu-devel@nongnu.org; Thu, 02 Oct 2025 15:37:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1759433853; 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=8+62xipTed+m1KXNcPWagaWg0W7396sbvQSbiZ6zpN0=; b=hdOJY/px5M9lbP98z/hJ0QI7Nzox8925W48hGO42+H6t8iXL2Me2pU3Vjh6E5R0U2WcPmP 1CuhrNdPVd18SxaXKS1OhMeK938Qre0PuQK2DLtQ0G2hmUgPUUCGeydOAG9iaL+t+tyFYa sQasRi04ivbNfgvyLTLiJsUhk8virWc= Received: from mx-prod-mc-02.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-399-b0c_n4eLPmaiBhAkmt_7OA-1; Thu, 02 Oct 2025 15:37:32 -0400 X-MC-Unique: b0c_n4eLPmaiBhAkmt_7OA-1 X-Mimecast-MFC-AGG-ID: b0c_n4eLPmaiBhAkmt_7OA_1759433851 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E9E7D195608A; Thu, 2 Oct 2025 19:37:30 +0000 (UTC) Received: from localhost (unknown [10.2.16.139]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4E6B31800577; Thu, 2 Oct 2025 19:37:30 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Kevin Wolf , qemu-block@nongnu.org, Jean-Louis Dupond , Hanna Reitz , Stefan Hajnoczi Subject: [PATCH 2/3] block: use pwrite_zeroes_alignment when writing first sector Date: Thu, 2 Oct 2025 14:39:59 -0400 Message-ID: <20251002184000.410486-3-stefanha@redhat.com> In-Reply-To: <20251002184000.410486-1-stefanha@redhat.com> References: <20251002184000.410486-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.451, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_PASS=-0.001, T_SPF_HELO_TEMPERROR=0.01 autolearn=ham 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 Since commit 5634622bcb33 ("file-posix: allow BLKZEROOUT with -t writeback"), qemu-img create errors out on a Linux loop block device with a 4 KB sector size: # dd if=/dev/zero of=blockfile bs=1M count=1024 # losetup --sector-size 4096 /dev/loop0 blockfile # qemu-img create -f raw /dev/loop0 1G Formatting '/dev/loop0', fmt=raw size=1073741824 qemu-img: /dev/loop0: Failed to clear the new image's first sector: Invalid argument Use the pwrite_zeroes_alignment block limit to avoid misaligned fallocate(2) or ioctl(BLKZEROOUT) in the block/file-posix.c block driver. Fixes: 5634622bcb33 ("file-posix: allow BLKZEROOUT with -t writeback") Reported-by: Jean-Louis Dupond Buglink: https://gitlab.com/qemu-project/qemu/-/issues/3127 Signed-off-by: Stefan Hajnoczi --- include/system/block-backend-io.h | 1 + block.c | 3 ++- block/block-backend.c | 11 +++++++++++ 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/include/system/block-backend-io.h b/include/system/block-backend-io.h index ba8dfcc7d0..6d5ac476fc 100644 --- a/include/system/block-backend-io.h +++ b/include/system/block-backend-io.h @@ -116,6 +116,7 @@ BlockAIOCB *blk_abort_aio_request(BlockBackend *blk, void *opaque, int ret); uint32_t blk_get_request_alignment(BlockBackend *blk); +uint32_t blk_get_pwrite_zeroes_alignment(BlockBackend *blk); uint32_t blk_get_max_transfer(BlockBackend *blk); uint64_t blk_get_max_hw_transfer(BlockBackend *blk); diff --git a/block.c b/block.c index 8848e9a7ed..be77e03904 100644 --- a/block.c +++ b/block.c @@ -606,12 +606,13 @@ create_file_fallback_zero_first_sector(BlockBackend *blk, int64_t current_size, Error **errp) { + uint32_t alignment = blk_get_pwrite_zeroes_alignment(blk); int64_t bytes_to_clear; int ret; GLOBAL_STATE_CODE(); - bytes_to_clear = MIN(current_size, BDRV_SECTOR_SIZE); + bytes_to_clear = MIN(current_size, MAX(BDRV_SECTOR_SIZE, alignment)); if (bytes_to_clear) { ret = blk_co_pwrite_zeroes(blk, 0, bytes_to_clear, BDRV_REQ_MAY_UNMAP); if (ret < 0) { diff --git a/block/block-backend.c b/block/block-backend.c index f8d6ba65c1..239d6eca37 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -2305,6 +2305,17 @@ uint32_t blk_get_request_alignment(BlockBackend *blk) return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE; } +/* Returns the optimal write zeroes alignment, in bytes; guaranteed nonzero */ +uint32_t blk_get_pwrite_zeroes_alignment(BlockBackend *blk) +{ + BlockDriverState *bs = blk_bs(blk); + IO_CODE(); + if (!bs) { + return BDRV_SECTOR_SIZE; + } + return bs->bl.pwrite_zeroes_alignment ?: bs->bl.request_alignment; +} + /* Returns the maximum hardware transfer length, in bytes; guaranteed nonzero */ uint64_t blk_get_max_hw_transfer(BlockBackend *blk) { -- 2.51.0