Date: Mon, 13 Dec 2021 16:26:42 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: FreeBSD Current <freebsd-current@freebsd.org> Subject: RFC: What to do about Allocate in the NFS server for FreeBSD13? Message-ID: <YQXPR0101MB0968EEFD5AE3B86F1D2DF667DD749@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>
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Hi,=0A=
=0A=
There are two problems with Allocate in the NFSv4.2 server in FreeBSD13:=0A=
1 - It uses the thread credentials instead of the ones for the RPC.=0A=
2 - It does not ensure that file changes are committed to stable storage.=
=0A=
These problems are fixed by commit f0c9847a6c47 in main, which added=0A=
ioflag and cred arguments to VOP_ALLOCATE().=0A=
=0A=
I can think of 3 ways to fix Allocate in FreeBSD13:=0A=
1 - Apply a *hackish* patch like this:=0A=
+ savcred =3D p->td_ucred;=0A=
+ td->td_ucred =3D cred;=0A=
do {=0A=
olen =3D len;=0A=
error =3D VOP_ALLOCATE(vp, &off, &len);=0A=
if (error =3D=3D 0 && len > 0 && olen > len)=0A=
maybe_yield();=0A=
} while (error =3D=3D 0 && len > 0 && olen > len);=0A=
+ p->td_ucred =3D savcred;=0A=
if (error =3D=3D 0 && len > 0)=0A=
error =3D NFSERR_IO;=0A=
+ if (error =3D=3D 0)=0A=
+ error =3D VOP_FSYNC(vp, MNT_WAIT, p);=0A=
The worst part of it is temporarily setting td_ucred to cred.=0A=
=0A=
2 - MFC'ng commit f0c9847a6c47. Normally changes to the=0A=
VOP/VFS are not MFC'd. However, in this case, it might be=0A=
ok to do so, since it is unlikely there is an out of source tree=0A=
file system with a custom VOP_ALLOCATE() method?=0A=
=0A=
3 - Just disable it. Currently it is disabled by default and it=0A=
could just be wired down disabled.=0A=
Allocate is not that useful, since ZFS does not support it.=0A=
=0A=
As an aside to this, the IETF NFSv4 working group seems to=0A=
have agreed that NFS4ERR_NOTSUPP can be returned by a=0A=
NFSv4.2 server on a 'per file system basis" instead of globally,=0A=
since the Linux knfsd already does this.=0A=
--> As such, Allocate can be enabled by default in main and=0A=
could be enabled by default in FreeBSD13, if #1 or #2 was=0A=
done.=0A=
--> It still would not work for ZFS exports.=0A=
=0A=
So, what do you think is the preferred alternative?=0A=
=0A=
rick=0A=
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