[PATCH v2 4/5] nbd: remove queue freeze in nbd_add_socket

[Yang Erkun <yangerkun@huawei.com>]

From: Long Li <leo.lilong@huawei.com>

The queue freeze was originally needed to prevent concurrent requests
from accessing config->socks while the backing array was being
reallocated. Since config->socks is now an xarray, insertions are
safe under RCU without freezing the queue.

This significantly reduces connection setup time when using a large
number of connections (-C 256):

  before: real 4.510s
  after:  real 0.263s

Signed-off-by: Long Li <leo.lilong@huawei.com>
---
 drivers/block/nbd.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 409a655c40f0..953146c85f17 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1299,7 +1299,6 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	struct nbd_config *config = nbd->config;
 	struct socket *sock;
 	struct nbd_sock *nsock;
-	unsigned int memflags;
 	unsigned int index;
 	int err;
 
@@ -1311,12 +1310,6 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 		return err;
 	nbd_reclassify_socket(sock);
 
-	/*
-	 * We need to make sure we don't get any errant requests while we're
-	 * reallocating the ->socks array.
-	 */
-	memflags = blk_mq_freeze_queue(nbd->disk->queue);
-
 	if (!netlink && !nbd->task_setup &&
 	    !test_bit(NBD_RT_BOUND, &config->runtime_flags))
 		nbd->task_setup = current;
@@ -1353,12 +1346,10 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 
 	config->num_connections++;
 	atomic_inc(&config->live_connections);
-	blk_mq_unfreeze_queue(nbd->disk->queue, memflags);
 
 	return 0;
 
 put_socket:
-	blk_mq_unfreeze_queue(nbd->disk->queue, memflags);
 	sockfd_put(sock);
 	return err;
 }
-- 
2.52.0