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

[Liu Yuan]

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().

Thanks,
Yuan