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 258E222D7A2 for ; Thu, 13 Feb 2025 23:29:28 +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=1739489369; cv=none; b=LiYbK25lpT8l97vKoKoFIHYbUHWcdF97t7H+Hy3Mg9uVUWOWdlOmpBUKAF77m300af7yfP+6/j7a1SL9AIVPRm6GRc13sGpZ1u/LevKXtW+Ao0jcS88hbwR8k9Ye2Kc9c7yOyjpmmblBmrMOGFKICuJIMPcEMYL4VU/El2hXYDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739489369; c=relaxed/simple; bh=ROa3RujU5C5WGUX3MVfLv9WTL9Tnz+1cXzmjqjmAD/g=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=lKhkFXnscZsKB7kXOGCETBseBX30pSiXnefBPtY+9QCxwWd6dKaLDBYi2I5M5lYu/I6MTtm/oMXV5+i5hqtazxNzvQ5tzzLeFsbv0uUYo4KhuaZHYkeGoAPkqi8prfRYRB6Lj/s4wKC26foc6m0TT6b2fpvWbONX1CshGxSwgOk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mqL1L9W/; 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="mqL1L9W/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E38C8C4CED1; Thu, 13 Feb 2025 23:29:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1739489368; bh=ROa3RujU5C5WGUX3MVfLv9WTL9Tnz+1cXzmjqjmAD/g=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=mqL1L9W/UcuzVnY9mx8qE5cAWiMbfOJ9qq2c9msbod0Sj+8k9jeriQ15DFoVfbpii yc5WeNcj3W/sKF1LlQth1eMSRGoiEZPehMwtMECw9lnmkD8OsvdxGENjKz+ErQJUpP eZgJJs+TMHYPtCeYDwC8hJalslUcgmqvts4OAitZu3cJpFstq64rn0oBjbzZK9Y0tv OMUSoVd3DC4QOkhDlo0cE3Iv0oN75ynZSnusoYML3hojS0Y7hYu8GA5pDTwPNrsrPg AOFF1W4UndnihV5qIHz0EYrr/XH2SlqSd7tPdDkgtks2aB7J/0EnZBMys/4LSUPla7 OYnmQDGopEdaQ== Message-ID: <41f344362f8d1c7a3a3f72dbc8a904ffbccec189.camel@kernel.org> Subject: Re: [PATCH 2/2] NFSD: allow client to use write delegation stateid for READ From: Jeff Layton To: Dai Ngo , chuck.lever@oracle.com, neilb@suse.de, okorniev@redhat.com, tom@talpey.com Cc: linux-nfs@vger.kernel.org, sagi@grimberg.me Date: Thu, 13 Feb 2025 18:29:26 -0500 In-Reply-To: <5eeb042a0a6c69bba89e1334d6ceac872eda03e3.camel@kernel.org> References: <1739475438-5640-1-git-send-email-dai.ngo@oracle.com> <1739475438-5640-3-git-send-email-dai.ngo@oracle.com> <5eeb042a0a6c69bba89e1334d6ceac872eda03e3.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-02-13 at 16:07 -0500, Jeff Layton wrote: > On Thu, 2025-02-13 at 11:37 -0800, Dai Ngo wrote: > > Allow read using write delegation stateid granted on OPENs with > > OPEN4_SHARE_ACCESS_WRITE only, to accommodate clients whose WRITE > > implementation may unavoidably do (e.g., due to buffer cache > > constraints). > >=20 > > When this condition is detected in nfsd4_encode_read the access > > mode FMODE_READ is temporarily added to the file's f_mode and is > > removed when the read is done. > >=20 > > Signed-off-by: Dai Ngo > > --- > > fs/nfsd/nfs4proc.c | 15 ++++++++++++++- > > fs/nfsd/nfs4xdr.c | 8 ++++++++ > > fs/nfsd/xdr4.h | 1 + > > 3 files changed, 23 insertions(+), 1 deletion(-) > >=20 > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > > index f6e06c779d09..be43627bbf78 100644 > > --- a/fs/nfsd/nfs4proc.c > > +++ b/fs/nfsd/nfs4proc.c > > @@ -973,7 +973,18 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_co= mpound_state *cstate, > > /* check stateid */ > > status =3D nfs4_preprocess_stateid_op(rqstp, cstate, &cstate->current= _fh, > > &read->rd_stateid, RD_STATE, > > - &read->rd_nf, NULL); > > + &read->rd_nf, &read->rd_wd_stid); > > + /* > > + * rd_wd_stid is needed for nfsd4_encode_read to allow write > > + * delegation stateid used for read. Its refcount is decremented > > + * by nfsd4_read_release when read is done. > > + */ > > + if (!status && read->rd_wd_stid && > > + (read->rd_wd_stid->sc_type !=3D SC_TYPE_DELEG || > > + delegstateid(read->rd_wd_stid)->dl_type !=3D NFS4_OPEN_DELEGATE_WRIT= E)) { > > + nfs4_put_stid(read->rd_wd_stid); > > + read->rd_wd_stid =3D NULL; > > + } > > =20 > > read->rd_rqstp =3D rqstp; > > read->rd_fhp =3D &cstate->current_fh; > > @@ -984,6 +995,8 @@ nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_com= pound_state *cstate, > > static void > > nfsd4_read_release(union nfsd4_op_u *u) > > { > > + if (u->read.rd_wd_stid) > > + nfs4_put_stid(u->read.rd_wd_stid); > > if (u->read.rd_nf) > > nfsd_file_put(u->read.rd_nf); > > trace_nfsd_read_done(u->read.rd_rqstp, u->read.rd_fhp, > > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c > > index e67420729ecd..3996678bab3f 100644 > > --- a/fs/nfsd/nfs4xdr.c > > +++ b/fs/nfsd/nfs4xdr.c > > @@ -4498,6 +4498,7 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp,= __be32 nfserr, > > unsigned long maxcount; > > __be32 wire_data[2]; > > struct file *file; > > + bool wronly =3D false; > > =20 > > if (nfserr) > > return nfserr; > > @@ -4515,10 +4516,17 @@ nfsd4_encode_read(struct nfsd4_compoundres *res= p, __be32 nfserr, > > maxcount =3D min_t(unsigned long, read->rd_length, > > (xdr->buf->buflen - xdr->buf->len)); > > =20 > > + if (!(file->f_mode & FMODE_READ) && read->rd_wd_stid) { > > + /* allow READ using write delegation stateid */ > > + wronly =3D true; > > + file->f_mode |=3D FMODE_READ; > > + } >=20 > Is that really OK? Can we just upgrade the f_mode like that? >=20 > Also, what happens with more exotic exported filesystems like NFS?=C2=A0 >=20 > For example, if I'm reexporting NFS, the backend NFS server may not > allow you to do a READ operation using a OPEN4_SHARE_ACCESS_WRITE only > stateid. Won't this break in that case? >=20 Hmm...bad example since we don't allow delegations on reexported NFS these days. Reexporting Ceph or SMB might be a better example. They'll likely both have problems if you try to issue a read on the result from a O_WRONLY open. I think you will probably need to rework the way nfs4_file's track their struct files. IOW, when the client does a OPEN4_SHARE_ACCESS_WRITE-only open, you need to get a struct file that is FMODE_READ|FMODE_WRITE to hang off the delegation. But, you'll also need to fix up the accounting for the share/deny mode locking to ignore that you _actually_ have it open for read too in that case. Smoke and mirrors... > > if (file->f_op->splice_read && splice_ok) > > nfserr =3D nfsd4_encode_splice_read(resp, read, file, maxcount); > > else > > nfserr =3D nfsd4_encode_readv(resp, read, file, maxcount); > > + if (wronly) > > + file->f_mode &=3D ~FMODE_READ; > > if (nfserr) { > > xdr_truncate_encode(xdr, eof_offset); > > return nfserr; > > diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h > > index c26ba86dbdfd..2f053beed899 100644 > > --- a/fs/nfsd/xdr4.h > > +++ b/fs/nfsd/xdr4.h > > @@ -426,6 +426,7 @@ struct nfsd4_read { > > struct svc_rqst *rd_rqstp; /* response */ > > struct svc_fh *rd_fhp; /* response */ > > u32 rd_eof; /* response */ > > + struct nfs4_stid *rd_wd_stid; /* internal */ > > }; > > =20 > > struct nfsd4_readdir { >=20 --=20 Jeff Layton