bcache: fix miss key refill->end in writeback

BugLink: https://bugs.launchpad.net/bugs/1810947

commit 2d6cb6ed upstream.

refill->end record the last key of writeback, for example, at the first
time, keys (1,128K) to (1,1024K) are flush to the backend device, but
the end key (1,1024K) is not included, since the bellow code:
	if (bkey_cmp(k, refill->end) >= 0) {
		ret = MAP_DONE;
		goto out;
	}
And in the next time when we refill writeback keybuf again, we searched
key start from (1,1024K), and got a key bigger than it, so the key
(1,1024K) missed.
This patch modify the above code, and let the end key to be included to
the writeback key buffer.
Signed-off-by: Tang Junhui <tang.junhui.linux@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/md/bcache/btree.c

@@ -2372,7 +2372,7 @@ static int refill_keybuf_fn(struct btree_op *op, struct btree *b,
 	struct keybuf *buf = refill->buf;
 	int ret = MAP_CONTINUE;
 
-	if (bkey_cmp(k, refill->end) >= 0) {
+	if (bkey_cmp(k, refill->end) > 0) {
 		ret = MAP_DONE;
 		goto out;
 	}