Re: [PATCH] fsx: check for filesystem support of FALLOCATE_FL_KEEP_SIZE

[Boaz Harrosh <boaz@plexistor.com>]

On 02/05/2015 04:22 PM, Christoph Hellwig wrote:
> On Thu, Feb 05, 2015 at 04:16:19PM +0200, Boaz Harrosh wrote:
>> On 02/03/2015 11:09 PM, Anna Schumaker wrote:
>>> The NFS implementation of fallocate() does not support passing the
>>> KEEP_SIZE flag by itself, causing tests to randomly fail.
>>>
>>
>> This I do not understand please explain. If all the other FSs just ignore
>> a trivial case, then why should NFS not ignore it the same as all
>> other filesystems.
>>
>> Why NFS is allowed to be special. (And apparently break user code xfs
>> being an example of one)
> 
> fsx is a test tool.  We've never guaranteed that a filesystem needs to
> support all or a special subset of fallocate options.
> 
> The NFSv4.2 protocol doesn't support preallocations beyond the file
> size, which is something I decided would be to horrible to refit into
> the NFS file abstraction when rewriting the preallocation / reservation
> section of the spec.

Ha OK now I understand. KEEP_SIZE is not supported when allocating blocks.

Pity, it is very useful for exactly those that need fallocte like video files.
Perhaps in the next version, thanks.

Boaz