Re: RFC: What to do about Allocate in the NFS server for FreeBSD13?

On 12/13/21 8:30 AM, Konstantin Belousov wrote:
> 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.

I also think this is fine.

-- 
John Baldwin