| From d5039b9b4833a5e7d8cabb87ba6c54f9ade9b022 Mon Sep 17 00:00:00 2001 |
| From: Josef Bacik <jbacik@fb.com> |
| Date: Thu, 19 Jan 2017 16:08:49 -0500 |
| Subject: 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> |
| --- |
| drivers/block/nbd.c | 6 ++---- |
| 1 file changed, 2 insertions(+), 4 deletions(-) |
| |
| diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c |
| index 4d30da269060..42a53956aefe 100644 |
| --- a/drivers/block/nbd.c |
| +++ b/drivers/block/nbd.c |
| @@ -269,7 +269,7 @@ static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec, |
| 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 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd) |
| if (type != NBD_CMD_WRITE) |
| return 0; |
| |
| - flags = 0; |
| bio = req->bio; |
| while (bio) { |
| struct bio *next = bio->bi_next; |
| @@ -318,9 +317,8 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd) |
| |
| 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); |
| -- |
| 2.17.1 |
| |
