nbd: only set MSG_MORE when we have more to send
[ Upstream commit d61b7f972dab2a7d187c38254845546dfc8eed85 ]
A user noticed that write performance was horrible over loopback and we
traced it to an inversion of when we need to set MSG_MORE. It should be
set when we have more bvec's to send, not when we are on the last bvec.
This patch made the test go from 20 iops to 78k iops.
Signed-off-by: Josef Bacik <jbacik@fb.com>
Fixes: 429a787be679 ("nbd: fix use-after-free of rq/bio in the xmit path")
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 4d30da2..42a5395 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -269,7 +269,7 @@
static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd)
{
struct request *req = blk_mq_rq_from_pdu(cmd);
- int result, flags;
+ int result;
struct nbd_request request;
unsigned long size = blk_rq_bytes(req);
struct bio *bio;
@@ -309,7 +309,6 @@
if (type != NBD_CMD_WRITE)
return 0;
- flags = 0;
bio = req->bio;
while (bio) {
struct bio *next = bio->bi_next;
@@ -318,9 +317,8 @@
bio_for_each_segment(bvec, bio, iter) {
bool is_last = !next && bio_iter_last(bvec, iter);
+ int flags = is_last ? 0 : MSG_MORE;
- if (is_last)
- flags = MSG_MORE;
dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
cmd, bvec.bv_len);
result = sock_send_bvec(nbd, &bvec, flags);