From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CF92E34D3A3 for ; Thu, 6 Nov 2025 04:15:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762402537; cv=none; b=OhmVn19SaPCOnC1UhfuFIA8sV/lt5SFOpJbJ52pEULRwa8hT511mV7qbKWYqpApBmEQC4zS5N46kTg9M/5LISOnVockzYxu5gJLSTeYwHDmngL/VbdThJx8zw5yR0FbTuEqt+SWUyWb9q8irRdBD2/aL3o2rClNOcfZweyQRrVM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762402537; c=relaxed/simple; bh=/sOH+pgI1B7Zksc65FcyMsf/zxNQTubm6OwAU648qY8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=im/I0SlsI7yGBcjnWQAi14nvzDou5h19u7JilFjrSacVXTSny3bqhgyN0wujWQQWAIi5iCcPsD314z3fg6KR2pspXCwx3wn9Xv90hcUyIuwtr8RK3wTLea1eOAb9rLkTenRdZ3OEC+yCi0o4n+JUXXJjhNrsM6t9+CO7N4DFrhg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=o+GjAkc0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="o+GjAkc0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84337C4CEFB; Thu, 6 Nov 2025 04:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762402536; bh=/sOH+pgI1B7Zksc65FcyMsf/zxNQTubm6OwAU648qY8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=o+GjAkc0Nu+87w+iDyIudEWXQlWjCif6XyqoQxEgFZ89D4SjitgBcI/Dox/n3BsiN cxiISJERCJLK8Nsbk2j4wk2xcJQgH1KqDrzL3IIL5LOcSnEVIt3wxILTBLCTaHg8Yg et91SV4z0eMJaKwos5l1Popy/srn8aO0K6CHZmVplle0k9N+Cqe4TBHUnJJxtoSPUP Sdr04kPtfVwYO8G7RNELiQDjpruGexiziSdZCKN33qRH9lbnkvMooqhsWMgkIsX+zG ePnDR9I/6FCexABMqbOB6FM9bVsOvdgar3dYjpamEXibgSoP/r43kr1unBk8pgmktm vVMd3NbfA5Cxw== Message-ID: <2f396cf1-3f8f-43a8-923d-b073f73f2cd7@kernel.org> Date: Thu, 6 Nov 2025 13:11:42 +0900 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2 0/4] null_blk: relaxed memory alignments To: Keith Busch , linux-block@vger.kernel.org, hch@lst.de, axboe@kernel.dk, hans.holmberg@wdc.com Cc: Keith Busch References: <20251106015447.1372926-1-kbusch@meta.com> From: Damien Le Moal Content-Language: en-US Organization: Western Digital Research In-Reply-To: <20251106015447.1372926-1-kbusch@meta.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/6/25 10:54 AM, Keith Busch wrote: > From: Keith Busch > > The direct-io can work with arbitrary memory alignemnts, based on what > the block device's queue limits report. This series enhances the > null_blk driver by removing the software limitations that required > block size memory and length alignment. > > Note, funny thing I noticed: this patch could allow null_blk to use > byte aligned memory, but the queue limits doesn't have a way to express > that. The smallest we can set the mask is 1, meaning 2-byte alignment, > because setting the mask to 0 is overridden by the default 511 mask. I'm > pretty sure at least some drivers are depending on the default, so can't > really change that. Maybe we could special case UINT_MAX for the no restriction case ? -- Damien Le Moal Western Digital Research