Re: [PATCH v2 2/3] NFSv4.1: Always clear the NFS_INO_LAYOUTCOMMIT in layoutreturn

[Boaz Harrosh <bharrosh@panasas.com>]

On 03/21/2013 07:06 PM, Peng Tao wrote:
> On Thu, Mar 21, 2013 at 10:13:00AM -0400, Trond Myklebust wrote:
> <snip>
>> @@ -1458,7 +1479,6 @@ static void pnfs_ld_handle_write_error(struct nfs_write_data *data)
>>  	dprintk("pnfs write error = %d\n", hdr->pnfs_error);
>>  	if (NFS_SERVER(hdr->inode)->pnfs_curr_ld->flags &
>>  	    PNFS_LAYOUTRET_ON_ERROR) {
>> -		clear_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(hdr->inode)->flags);
> Hi Trond and Boaz,
> 
> If object layout requires layout being committed before returned (as fixed in
> the 3/3 patch), is it a potential problem to directly return layout here as
> well? e.g., if one lseg is successfully written and pending layoutcommit,
> then another lseg of the same file failed read/write, then layout will be
> returned w/o layoutcommit. For blocklayout, it is a potential data corruption
> and that's why block layout doesn't set PNFS_LAYOUTRET_ON_ERROR bit. So
> I'm wondering if object will suffer from the same issue?
> 

Hi Tao

No, not at all. The objects layout has error reported as part of the
layout_return OPT. With exact devices that failed and why. In fact the
data should not be "committed" per ce, but a recovery process must be
preformed because we know that not all data of a stripe was committed
including parity, and the raid5 check-some is surly wrong. This is why
there is an error bit in layout_commit OPT to denote that this is not
a true commit and that there is an Error report on the way, for those
clients that must always lo_commit before lo_return even on Error.

(I know that 4.2 has plans for error-report RETURNs for other layout
 types as well, this is part of why)

> Thanks,
> Tao
> 

Cheers
Boaz