lightnvm: pblk: rollback on error during gc read

A line is left unsigned to the blocks lists in case pblk_gc_line
returns an error.

This moves the line back to be appropriate list, which can then be
picked up by the garbage collector.
Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
Reviewed-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-gc.c

@@ -358,8 +358,13 @@ static int pblk_gc_read(struct pblk *pblk)
 
 	pblk_gc_kick(pblk);
 
-	if (pblk_gc_line(pblk, line))
+	if (pblk_gc_line(pblk, line)) {
 		pblk_err(pblk, "failed to GC line %d\n", line->id);
+		/* rollback */
+		spin_lock(&gc->r_lock);
+		list_add_tail(&line->list, &gc->r_list);
+		spin_unlock(&gc->r_lock);
+	}
 
 	return 0;
 }