[sheepdog] [PATCH 2/2] farm: recover object from omap when trunk is not found

[MORITA Kazutaka]

At Wed, 08 Aug 2012 13:45:09 +0800,
Liu Yuan wrote:
> 
> On 08/07/2012 09:11 PM, MORITA Kazutaka wrote:
> > +		/* retrieve_object_from_snap fails while farm_end_recover is
> > +		 * ongoing because the trunk object is not created yet.
> > +		 * Let's get the sha1 value from omap in that case.*/
> > +		if (!buffer) {
> > +			unsigned char *sha1;
> > +			struct sha1_file_hdr h;
> > +
> > +			sha1 = get_sha1_from_omap(oid);
> > +			if (sha1)
> > +				buffer = sha1_file_read(sha1, &h);
> > +
> > +			dprintf("retrieve object %"PRIx64" with omap, %s\n",
> > +				oid, buffer ? "succeed" : "fail");
> > +		}
> >  		if (!buffer)
> >  			return SD_RES_NO_OBJ;
> >  		memcpy(iocb->buf, buffer, iocb->length);
> 
> This patch might work, but we don't handle partial read_working_object
> gracefully: we simply return NULL and try to get sha1 from omap as a
> workaround.
> 
> I'd suggest following fix:
>  in trunk_file_write_recovery()
>    1. generate sha1 for all the stale oid, remove all the stale oid from
> the trunk_active_list and splice to a temp remove tree
>    2 write trunk sha1
>    3 if success, then remove all the object from working directory.
> 
> In this way, we don't need expose omap outside trunk and no need to
> modify the logic of farm_read().

Agreed, that's a better approach.

Thanks,

Kazutaka