Re: [RFC] spnfs-block: restore i_op->fallocate

[Benny Halevy <bhalevy@panasas.com>]

On 2011-03-30 19:33, Christoph Hellwig wrote:

> On Wed, Mar 30, 2011 at 07:11:47PM +0200, Benny Halevy wrote:
>> Makes sense. This could also be done by adding a respective flags argument
>> to fallocate and have a common wrapper function look at the file descriptor
>> and call the fs fallocate, that could then get the inode rather the file.
>> In other words, why copy code rather than factor it out into a common
>> function?
> We can discuss that _iff_ a valid use for a file-less fallocate appears
> in mainline.  The pnfs-block one is not.  It's just a racy hack, which
> opens gapping holes.  Take a look what it does - it allocates block for
> a client to write into directly, with absolutely zero guarantee the
> block allocation actually stays around until that point.
>
> You'll need to have some outstanding token on extent map changes like
> done in CXFS or NEC's "gfs" which implemented something similar to pnfs
> based on nfsv3.

Agreed.

Benny

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