Date: Mon, 13 Dec 2021 18:30:44 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: RFC: What to do about Allocate in the NFS server for FreeBSD13? Message-ID: <Ybd1NFXuRjM5W1zj@kib.kiev.ua> In-Reply-To: <YQXPR0101MB0968EEFD5AE3B86F1D2DF667DD749@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM> References: <YQXPR0101MB0968EEFD5AE3B86F1D2DF667DD749@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>
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On Mon, Dec 13, 2021 at 04:26:42PM +0000, Rick Macklem wrote:
> Hi,
>
> There are two problems with Allocate in the NFSv4.2 server in FreeBSD13:
> 1 - It uses the thread credentials instead of the ones for the RPC.
> 2 - It does not ensure that file changes are committed to stable storage.
> These problems are fixed by commit f0c9847a6c47 in main, which added
> ioflag and cred arguments to VOP_ALLOCATE().
>
> I can think of 3 ways to fix Allocate in FreeBSD13:
> 1 - Apply a *hackish* patch like this:
> + savcred = p->td_ucred;
> + td->td_ucred = cred;
> do {
> olen = len;
> error = VOP_ALLOCATE(vp, &off, &len);
> if (error == 0 && len > 0 && olen > len)
> maybe_yield();
> } while (error == 0 && len > 0 && olen > len);
> + p->td_ucred = savcred;
> if (error == 0 && len > 0)
> error = NFSERR_IO;
> + if (error == 0)
> + error = VOP_FSYNC(vp, MNT_WAIT, p);
> The worst part of it is temporarily setting td_ucred to cred.
>
> 2 - MFC'ng commit f0c9847a6c47. Normally changes to the
> VOP/VFS are not MFC'd. However, in this case, it might be
> ok to do so, since it is unlikely there is an out of source tree
> file system with a custom VOP_ALLOCATE() method?
I do not see much wrong with #2, this is what I would do myself.
>
> 3 - Just disable it. Currently it is disabled by default and it
> could just be wired down disabled.
> Allocate is not that useful, since ZFS does not support it.
>
> As an aside to this, the IETF NFSv4 working group seems to
> have agreed that NFS4ERR_NOTSUPP can be returned by a
> NFSv4.2 server on a 'per file system basis" instead of globally,
> since the Linux knfsd already does this.
> --> As such, Allocate can be enabled by default in main and
> could be enabled by default in FreeBSD13, if #1 or #2 was
> done.
> --> It still would not work for ZFS exports.
>
> So, what do you think is the preferred alternative?
>
> rick
>
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