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 4ED5C24A7E9; Wed, 15 Jan 2025 14:24:23 +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=1736951063; cv=none; b=jziqTcGfpEoLOTAutc9B6cG/kls8rpUcjr6LzyYrP2wACAZpl4LCo4bLefUq9MLDlpk3w7GrXscbmH659UIUZdMSc0AOBcRJJmmSu8u+Amk9fzrFFBjZQDOfy/zBsITT4gLCbd0CXJ36uKvupaHioSHAYkMXvWHwPXKP3r0q8zY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736951063; c=relaxed/simple; bh=RD900BcbTxpWahAUZvGqF9air9wfkpsa/A0lwYaWpxY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=r0ipZ+O1uf1fI2FazzMf89f0Fay4pbVzdrU9WpfScrE67kGfhabd7BEx+ZOm8FBGlzkPBJCUrlvwrEESh5jnfiI8VDOMAqdG36yBlOpwR/uHy9zZlGdHQ2UVQwfaKmDXC+Ma1GvpuLARio6+bi+S94g6s5wyWzOUyolH8d6cb0s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SkhrnTJ8; 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="SkhrnTJ8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BFE94C4CED1; Wed, 15 Jan 2025 14:24:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736951063; bh=RD900BcbTxpWahAUZvGqF9air9wfkpsa/A0lwYaWpxY=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=SkhrnTJ8EimFUC3t9q7D9niigNgCq2EHHyxC8a+y/W563bWHYu+30fS0DNJNenvbn UiNHmhfx9XoZS6cFsmN12IhDClq4MfFO5P81clPTaz/zuTTh0rI3NYRP6I7ArRVvoG 4Uo7TSYQLRxJe6mXaTUN46MFVaoJqGyUEWSiq3oG3Wo+ojh83m5BTX6IMvVQa6GXQU uKD7VwJYq0uGx+EcnF28sv77G0wPwlxBLPdGfMeE8Csr+qwcL/F1Q0G6EbcBR2s2cm 4YHXM+qQ7hDjP0CmYskc3kWtuHWTmdriJ9LTHgH36V15GIcs8M/fJnuI37VXIfuTo2 x0S0L6eSwX05g== Message-ID: <0116f16a917aa56fa9350f801c48d4edc81ce70f.camel@kernel.org> Subject: Re: [LSF/MM/BPF TOPIC] Implementing the NFS v4.2 WRITE_SAME operation: VFS or NFS ioctl() ? From: Jeff Layton To: Anna Schumaker , lsf-pc@lists.linux-foundation.org Cc: linux-fsdevel@vger.kernel.org, Linux NFS Mailing List Date: Wed, 15 Jan 2025 09:24:21 -0500 In-Reply-To: References: Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE 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AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.2 (3.54.2-1.fc41) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-01-14 at 16:38 -0500, Anna Schumaker wrote: > I've seen a few requests for implementing the NFS v4.2 WRITE_SAME [1] ope= ration over the last few months [2][3] to accelerate writing patterns of da= ta on the server, so it's been in the back of my mind for a future project.= I'll need to write some code somewhere so NFS & NFSD can handle this reque= st. I could keep any implementation internal to NFS / NFSD, but I'd like to= find out if local filesystems would find this sort of feature useful and i= f I should put it in the VFS instead. > > I was thinking I could keep it simple, and model a function call based on= write(3) / pwrite(3) to write some pattern N times starting at either the = file's current offset or at a user-provide offset. Something like: > write_pattern(int filedes, const void *pattern, size_t nbytes, size_t= count); > pwrite_pattern(int filedes, const void *pattern, size_t nbytes, size_= t count, offset_t offset); >=20 These should also get flags fields, for sure. > I could then construct a WRITE_SAME call in the NFS client using this inf= ormation. This seems "good enough" to me for what people have asked for, at= least as a client-side interface. It wouldn't really help the server, whic= h would still need to do several writes in a loop to be spec-compliant with= writing the pattern to an offset inside the "application data block" [4] s= tructure. >=20 > But maybe I'm simplifying this too much, and others would find the additi= onal application data block fields useful? Or should I keep it all inside N= FS, and call it with an ioctl instead of putting it into the VFS? >=20 > Thoughts? > Anna >=20 > [1]: https://datatracker.ietf.org/doc/html/rfc7862#section-15.12 > [2]: https://lore.kernel.org/linux-nfs/CAAvCNcByQhbxh9aq_z7GfHx+_=3DS8zVc= r9-04zzdRVLpLbhxxSg@mail.gmail.com/ > [3]: https://lore.kernel.org/linux-nfs/CALWcw=3DGg33HWRLCrj9QLXMPME=3Dpnu= Zx_tE4+Pw8gwutQM4M=3Dvw@mail.gmail.com/ > [4]: https://datatracker.ietf.org/doc/html/rfc7862#section-8.1 >=20 I'd say keep it as an ioctl for now until we have at least one other filesystem (smb/client? fs/ceph?) that can implement this natively somehow. My worry here is that we would build these new syscalls, and then find that other filesystems need subtly different semantics for this, and then we have to scramble to shoehorn those in later. Are there are already other existing ioctls on other filesystems for similar operations? --=20 Jeff Layton