ore: Fix crash in case of an IO error.

The users of ore_check_io() expect the reported device
(In case of error) to be indexed relative to the passed-in
ore_components table, and not the logical dev index.

This causes a crash inside objlayoutdriver in case of
an IO error.

[Bug in 3.2.0 Kernel]
CC: Stable Tree <stable@kernel.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

fs/exofs/ore.c

@@ -445,10 +445,10 @@ int ore_check_io(struct ore_io_state *ios, ore_on_dev_error on_dev_error)
 			u64 residual = ios->reading ?
 					or->in.residual : or->out.residual;
 			u64 offset = (ios->offset + ios->length) - residual;
-			struct ore_dev *od = ios->oc->ods[
-					per_dev->dev - ios->oc->first_dev];
+			unsigned dev = per_dev->dev - ios->oc->first_dev;
+			struct ore_dev *od = ios->oc->ods[dev];
 
-			on_dev_error(ios, od, per_dev->dev, osi.osd_err_pri,
+			on_dev_error(ios, od, dev, osi.osd_err_pri,
 				     offset, residual);
 		}
 		if (osi.osd_err_pri >= acumulated_osd_err) {