From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 78D8241A76F for ; Thu, 16 Jul 2026 12:29:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784204972; cv=none; b=WmuYvhihdNlDOD3WweTzKQw8QaduMEP5XYDehexZFQM7Qt14Sxv4MC8QodyQM4ryD9v2KctuX8JHljeNqXkbjlSNNSaMm0pPdAcukDF2i/YfeRLK5DGlWCTIhKe6qhfI2vQirnngn1MJJUyA29CLhPUjmzR8/8buyaqVwWfBZMY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784204972; c=relaxed/simple; bh=C/6cGv/lh+CO2Afr/IiPdAUrYaT3SaP2cpXaXX223lA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=nqEaAyuUMZjhRjK/79WD/32UoAknSwBcE29cIR3A/NpBxr2DW4YDYIY5kv0kuJDi3/8Oyh+tvtgrjsc5KRQDQh6zyDnVvMKmquYCPP+MCbuh0SH4/8EmH4bCdo2xJFEs0YcPkbDbY7Zlt+7sAJ+bvXYqr22QI3f9642Sp6zePeM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OYjwuM/Z; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OYjwuM/Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7563A1F00A3A; Thu, 16 Jul 2026 12:29:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784204971; bh=FGOEAjD5cJg0KOqQUtXVtGfFcOKGbrimqwmp3FDk/2U=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=OYjwuM/ZqPaH2SF+3RGdyNnefkifdObx4AuV8Nqweub8rCyRBaaeTXiIElzWFx5Td PqSkxuu0yHKcPiq22qb9QXtorspxY+fYuOCaM1ewIqPD7DIhhg8jthEG79sTf5VVF6 jG3s0cmsworqS+PGeikFPVBJiAaRwFGitzxCeZXRbLZS23JXsxDq0KjQeXa6DKTDuG t7Ozav0vKYfnRHto1vpxUv4ejUoC12aFKjLpGm4Y7b4oglvnpjYG9nhEnc7GMxHsp5 b1f+cjIGBL2wN/9m9F1qhdy7gLhz2w2OVxZeD+lMsM63w2Ab7UtcZ0yFaQ9wwa1NrH wxFVfEYqqLa1A== Message-ID: Subject: Re: [PATCH v3 14/17] nfsd: reduce want-write range in nfsd4_create_file() From: Jeff Layton To: NeilBrown , Chuck Lever Cc: Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org Date: Thu, 16 Jul 2026 08:29:28 -0400 In-Reply-To: <20260713062219.6399-15-neilb@ownmail.net> References: <20260713062219.6399-1-neilb@ownmail.net> <20260713062219.6399-15-neilb@ownmail.net> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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nfsd4_create_file() needs write access to the mount for two purposes: >=20 > 1/ to create/open the file. > 2/ to set attributes on the newly created (or pre-existing) file. >=20 > Currently this is all handled by holding the write access across the > open and the setattr. A subsequent patch will necessarily change how > write access is gained for the open. So we reduce the range for the > first want_write, and add another one to cover setattr. If we failed to > get write access, it is only fatal if there were attrs to set. >=20 > We call nfsd_create_setattr() if at all possible, even when no attrs, as > it also calls commit_metadata and we need to be certain that the file > creation has been synced. If the mount became read-only since the > creation happened, we can safely assume that the sync happened as part > of that. >=20 > Signed-off-by: NeilBrown > --- > fs/nfsd/nfs4proc.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) >=20 > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index adfc1f5ccd98..0d1bcb12ecbc 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -344,6 +344,8 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_= fh *fhp, > &QSTR_LEN(open->op_fname, open->op_fnamelen)); > if (IS_ERR(child)) { > status =3D nfserrno(PTR_ERR(child)); > + if (!want_write_err) > + fh_drop_write(fhp); > goto out; > } > path.dentry =3D child; > @@ -378,6 +380,8 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_= fh *fhp, > } > } > end_creating(child); > + if (!want_write_err) > + fh_drop_write(fhp); > if (status !=3D nfs_ok) > goto out; > =20 > @@ -421,7 +425,16 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc= _fh *fhp, > if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size =3D=3D 0)) > iap->ia_valid &=3D ~ATTR_SIZE; > =20 > - status =3D nfsd_create_setattr(rqstp, fhp, resfhp, &attrs); > + /* We will need write access to set the attrs */ > + want_write_err =3D fh_want_write(fhp); > + if (!want_write_err) { > + status =3D nfsd_create_setattr(rqstp, fhp, > + resfhp, &attrs); > + fh_drop_write(fhp); > + } else if (nfsd_attrs_valid(&attrs)) { > + /* Needed write access */ > + status =3D nfserrno(want_write_err); > + } > =20 > if (attrs.na_labelerr) > open->op_bmval[2] &=3D ~FATTR4_WORD2_SECURITY_LABEL; > @@ -432,8 +445,6 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_= fh *fhp, > if (attrs.na_paclerr) > open->op_bmval[2] &=3D ~FATTR4_WORD2_POSIX_ACCESS_ACL; > out: > - if (!want_write_err) > - fh_drop_write(fhp); > nfsd_attrs_free(&attrs); > return status; > } It sucks that file creation is so fraught with peril and places that things can go wrong and leave stuff sitting out on the fs. I wonder if we ought to be using O_TMPFILE where possible to do all of this setup and only later link it into the namespace. That's a much bigger change though of course. Reviewed-by: Jeff Layton