posix_fallocate on ZFS

[Willem Jan Withagen]

On 10/02/2018 20:43, Ian Lepore wrote:
> On Sat, 2018-02-10 at 11:24 -0700, Alan Somers wrote:
>> On Sat, Feb 10, 2018 at 10:28 AM, Willem Jan Withagen
>> wrote:
>>
>>>
>>> Hi,
>>>
>>> This has been disabled on ZFS since last November.
>>> And I do understand the rationale on this.
>>>
>>> BUT
>>>
>>> I've now upgraded some of my HEAD Ceph test systems and they now fail,
>>> since Ceph uses posix_fallocate() to allocate space for the
>>> FileStore-journal.
>>>
>>> Is there any expectation that this is going to fixed in any near future?
>>>
>>> --WjW
>>>
>> No.  It's fundamentally impossible to support posix_fallocate on a COW
>> filesystem like ZFS.  Ceph should be taught to ignore an EINVAL result,
>> since the system call is merely advisory.
>>
>> -Alan
> 
> Unfortunately, posix documents that the function returns EINVAL only
> due to bad input parameters, so ignoring that seems like a bad idea.
> 
> Wouldn't it be better if we returned EOPNOTSUP if that's the actual
> situation?  That could be safely ignored.

I would probably help in my situation....

And I've been looking at the manpage, but cannot seem to find any 
indication that EINVAL is returned on running it on FreeBSD.

--WjW