From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2574528D8DF for ; Tue, 18 Nov 2025 17:46:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763487974; cv=none; b=tAHQWwwuAWqRT00VyOwD/LepfnjSdVnFChXUIZM5ek+iXe5Qxr6UUSFXPcxQCFMcOkz9FoYY4Y0LMfT8hWMnDePnLq0i5P1AY5psSOkzYd2WA2VymQMn+97tKi702BsozTNBs45uG2xSCcxrsQfwqzsmIvVCsr8gjqDwsGu+9gA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763487974; c=relaxed/simple; bh=Uq5tdJmE6Xub5JGG6Pj2iyTFU40wozpXyX01LkAU6oA=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=LZcRXDrbiv8DGmkst7eQ00AxCP0IZOfglXicAujPicU39p32sbUEpXOE/K69LJpFYneKLB70HFmhMNL/S13YGoU3wR68mODhuxFLHu1NQ+zumLPTP24KxUOLwZtRcAD4w8A0QzG9sIQPCAwVckttwPB/fYaxHOJeerjGfhg1rQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XUNeSMlN; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XUNeSMlN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763487971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=G8901ol403sdgwix9HvW+bPtTpZJsvQHfZY+Qf5mb54=; b=XUNeSMlNLC5aNmURxnkJE4d3lJmqnxdDOfmXKZSYAoSh32QsX6wbYniNBAFmLGFjm6iyrs XhEEUQycgnjoo5VNYwVa/7qCCBUKPDMmJCAVjbik1hUA7Mu0dimnnrj46dBetZwG+Fi/Dx OO6WK1UDOtrQnfMgC+jaHSk6jkVxbKY= 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-540-2Pjm58uMOa-TN9bmlTAX6A-1; Tue, 18 Nov 2025 12:46:08 -0500 X-MC-Unique: 2Pjm58uMOa-TN9bmlTAX6A-1 X-Mimecast-MFC-AGG-ID: 2Pjm58uMOa-TN9bmlTAX6A_1763487967 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5230F1800372; Tue, 18 Nov 2025 17:46:07 +0000 (UTC) Received: from [10.44.32.60] (unknown [10.44.32.60]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 75DF3180087C; Tue, 18 Nov 2025 17:46:04 +0000 (UTC) Date: Tue, 18 Nov 2025 18:45:55 +0100 (CET) From: Mikulas Patocka To: Benjamin Marzinski cc: "Uladzislau Rezki (Sony)" , Alasdair Kergon , DMML , Andrew Morton , Mike Snitzer , Christoph Hellwig , LKML Subject: Re: [PATCH] dm-bufio: align write boundary on bdev_logical_block_size In-Reply-To: Message-ID: References: <20251020123350.2671495-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On Mon, 17 Nov 2025, Benjamin Marzinski wrote: > On Mon, Oct 20, 2025 at 02:48:13PM +0200, Mikulas Patocka wrote: > > > > > > On Mon, 20 Oct 2025, Uladzislau Rezki (Sony) wrote: > > > > > When performing a read-modify-write(RMW) operation, any modification > > > to a buffered block must cause the entire buffer to be marked dirty. > > > > > > Marking only a subrange as dirty is incorrect because the underlying > > > device block size(ubs) defines the minimum read/write granularity. A > > > lower device can perform I/O only on regions which are fully aligned > > > and sized to ubs. > > > > Hi > > > > I think it would be better to fix this in dm-bufio, so that other dm-bufio > > users would also benefit from the fix. > > This looks to me like it should accomplish the same thing as > Uladzislau's patch. But I think there could still be problems with other > dm-bufio users, for devices where the blocksize is larger than 4k. > > In dm_bufio_client_create() I think we want to make sure that block_size > is a multiple of bdev_logical_block_size(bdev), instead of 512b. I could add WARN_ON(block_size < bdev_logical_block_size(bdev)) to dm_bufio_client_create. But I think it's too late in this development cycle, I would add it after the next merge window closes, when I open a new patch series for the kernel 6.20 (or 7.0). > Otherwise block_to_sector() can return sectors that are not addressable > on the device. Unfortunatley, I don't think all users of dm-bufio will > pass in block_sizes that are larger than 4k (uds_make_bufio() in > dm-vdp/indexer/io-factory.c for instance). > > -Ben > > > Please try this patch - does it fix it? > > > > Mikulas I changed the patch below, so that it aligns write bios on max3(DM_BUFIO_WRITE_ALIGN, bdev_logical_block_size(b->c->bdev), bdev_physical_block_size(b->c->bdev)); - so that if physical block size is greater than logical block size, the writes are aligned so that the device doesn't do read-modify-write. Mikulas > > From: Mikulas Patocka > > > > There may be devices with logical block size larger than 4k. Fix > > dm-bufio, so that it will align I/O on logical block size. This commit > > fixes I/O errors on the dm-ebs target on the top of emulated nvme device > > with 8k logical block size created with qemu parameters: > > > > -device nvme,drive=drv0,serial=foo,logical_block_size=8192,physical_block_size=8192 > > > > Signed-off-by: Mikulas Patocka > > Cc: stable@vger.kernel.org > > > > --- > > drivers/md/dm-bufio.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > Index: linux-2.6/drivers/md/dm-bufio.c > > =================================================================== > > --- linux-2.6.orig/drivers/md/dm-bufio.c 2025-10-13 21:42:47.000000000 +0200 > > +++ linux-2.6/drivers/md/dm-bufio.c 2025-10-20 14:40:32.000000000 +0200 > > @@ -1374,7 +1374,7 @@ static void submit_io(struct dm_buffer * > > { > > unsigned int n_sectors; > > sector_t sector; > > - unsigned int offset, end; > > + unsigned int offset, end, align; > > > > b->end_io = end_io; > > > > @@ -1388,9 +1388,10 @@ static void submit_io(struct dm_buffer * > > b->c->write_callback(b); > > offset = b->write_start; > > end = b->write_end; > > - offset &= -DM_BUFIO_WRITE_ALIGN; > > - end += DM_BUFIO_WRITE_ALIGN - 1; > > - end &= -DM_BUFIO_WRITE_ALIGN; > > + align = max(DM_BUFIO_WRITE_ALIGN, bdev_logical_block_size(b->c->bdev)); > > + offset &= -align; > > + end += align - 1; > > + end &= -align; > > if (unlikely(end > b->c->block_size)) > > end = b->c->block_size; > > > > >