Commit 4b7c09a5 authored by Josef Bacik's avatar Josef Bacik Committed by Greg Kroah-Hartman

nbd: only set MSG_MORE when we have more to send

[ Upstream commit d61b7f97 ]

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: default avatarJosef Bacik <>
Fixes: 429a787b ("nbd: fix use-after-free of rq/bio in the xmit path")
Signed-off-by: default avatarJens Axboe <>
Signed-off-by: default avatarSasha Levin <>
parent 150b28b4
......@@ -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);
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