[PATCH 2/2] nbd: add support to replace running daemon
This patch allows userspace to switch daemons while IO is running or
to recovery from a crashed daemon. With the patch when using AF_UNIX
sockets and a local running daemon, the new daemon can perform a
NBD_CMD_RECONFIGURE nl command with the NBD_ATTR_SWAP_SOCKETS attr
set to 0. The kernel will then switch over to using the new socket
similar to how we handle failing over from a dead socket.
Signed-off-by: Mike Christie <mchristi@redhat.com>
---
drivers/block/nbd.c | 44 +++++++++++++++++++++++++++++---
include/uapi/linux/nbd-netlink.h | 1 +
2 files changed, 41 insertions(+), 4 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 06b63c11ae50..6aa396bea401 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1076,7 +1076,14 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
return 0;
}
-static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
+static bool nbd_requeue_req(struct request *req, void *data, bool reserved)
+{
+ nbd_requeue_cmd(blk_mq_rq_to_pdu(req));
+ return true;
+}
+
+static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg,
+ u8 swap_socks)
{
struct nbd_config *config = nbd->config;
struct socket *sock, *old;
@@ -1094,6 +1101,16 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
return -ENOMEM;
}
+ if (swap_socks) {
+ dev_dbg(disk_to_dev(nbd->disk), "stopping queue\n");
+
+ blk_mq_quiesce_queue(nbd->disk->queue);
+ send_disconnects(nbd);
+ sock_shutdown(nbd);
+ flush_workqueue(nbd->recv_workq);
+ blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_requeue_req, NULL);
+ }
+
for (i = 0; i < config->num_connections; i++) {
struct nbd_sock *nsock = config->socks[i];
@@ -1130,11 +1147,20 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
atomic_inc(&config->live_connections);
wake_up(&config->conn_wait);
- return 0;
+ err = 0;
+ goto start_queue;
}
sockfd_put(sock);
kfree(args);
- return -ENOSPC;
+ err = -ENOSPC;
+
+start_queue:
+ if (swap_socks) {
+ nbd->task_recv = current;
+ blk_mq_unquiesce_queue(nbd->disk->queue);
+ dev_dbg(disk_to_dev(nbd->disk), "queue restarted\n");
+ }
+ return err;
}
static void nbd_bdev_reset(struct block_device *bdev)
@@ -2027,6 +2053,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
{
struct nbd_device *nbd = NULL;
struct nbd_config *config;
+ u8 swap_socks = 0;
int index;
int ret = 0;
bool put_dev = false;
@@ -2107,6 +2134,15 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
}
}
+ if (info->attrs[NBD_ATTR_SWAP_SOCKETS]) {
+ swap_socks = nla_get_u8(info->attrs[NBD_ATTR_SWAP_SOCKETS]);
+ if (swap_socks != 1 && swap_socks != 0) {
+ printk(KERN_ERR "nbd: NBD_SOCK_SWAP must be 0 or 1\n");
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+
if (info->attrs[NBD_ATTR_SOCKETS]) {
struct nlattr *attr;
int rem, fd;
@@ -2132,7 +2168,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
if (!socks[NBD_SOCK_FD])
continue;
fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
- ret = nbd_reconnect_socket(nbd, fd);
+ ret = nbd_reconnect_socket(nbd, fd, swap_socks);
if (ret) {
if (ret == -ENOSPC)
ret = 0;
diff --git a/include/uapi/linux/nbd-netlink.h b/include/uapi/linux/nbd-netlink.h
index c5d0ef7aa7d5..0e406445f06c 100644
--- a/include/uapi/linux/nbd-netlink.h
+++ b/include/uapi/linux/nbd-netlink.h
@@ -35,6 +35,7 @@ enum {
NBD_ATTR_SOCKETS,
NBD_ATTR_DEAD_CONN_TIMEOUT,
NBD_ATTR_DEVICE_LIST,
+ NBD_ATTR_SWAP_SOCKETS,
__NBD_ATTR_MAX,
};
#define NBD_ATTR_MAX (__NBD_ATTR_MAX - 1)
--
2.21.0
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