Re: pnfs LD partial sector write

[Boaz Harrosh <bharrosh@panasas.com>]

On 07/26/2012 06:07 PM, Peng Tao wrote:

> On Thu, Jul 26, 2012 at 10:12 PM, Boaz Harrosh <bharrosh@panasas.com> wrote:
>> There is an easy locking solution for DIO which will not cost much
>> for DIO and will cost nothing for buffered IO. You use the page-cache
>> page lock.
>>
>> What you do is grab the zero-page of each block lock before/during writing to
>> any block. So for your example above they will all be serialized by page-zero
>> lock.
> Yeah, I agree this can work. But I'd prefer not to mix DIO with buffer
> IO, which is often error prone. If in any case I need to serialize
> AIODIO, I'd prefer to do it in easier ways like locking invalid
> extents etc, without messing with page cache.
> 


Ye, just keep it BLOCK aligned and that's it. Apps will learn fast enough.
Simple is always better.

Currently I support any alignment but I might do the same in objlayout in
the raid5/6 case. and DIO

<>

> Or maybe somehow through statfs(2), since the blocksize attribute is
> actually a file system's attribute instead of block device's.
> 


Good point!!
	statfs->f_bsize

man statfs:
  long    f_bsize;    /* optimal transfer block size */

What does NFS return in there now? maybe let LD override on that?

I'll support a patch as such we could use it as well.

Cheers
Boaz