bcache: Add a cond_resched() call to gc

Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Tested-by: NEric Wheeler <bcache@linux.ewheeler.net>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/md/bcache/btree.c

@@ -1741,6 +1741,7 @@ static void bch_btree_gc(struct cache_set *c)
 	do {
 		ret = btree_root(gc_root, c, &op, &writes, &stats);
 		closure_sync(&writes);
+		cond_resched();
 
 		if (ret && ret != -EAGAIN)
 			pr_warn("gc failed!");