nbd: Add the nbd NBD_DISCONNECT_ON_CLOSE config flag.

If NBD_DISCONNECT_ON_CLOSE is set on a device, then the driver will
issue a disconnect from nbd_release if the device has no remaining
bdev->bd_openers.

Fix ret val so reconfigure with only setting the flag succeeds.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 3b7083b..74a0556 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -76,6 +76,7 @@ struct link_dead_args {
 #define NBD_HAS_CONFIG_REF             4
 #define NBD_BOUND                      5
 #define NBD_DESTROY_ON_DISCONNECT      6
+#define NBD_DISCONNECT_ON_CLOSE        7
 
 struct nbd_config {
        u32 flags;
@@ -138,6 +139,7 @@ static void nbd_config_put(struct nbd_device *nbd);
 static void nbd_connect_reply(struct genl_info *info, int index);
 static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info);
 static void nbd_dead_link_work(struct work_struct *work);
+static void nbd_disconnect_and_put(struct nbd_device *nbd);
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
@@ -1305,6 +1307,12 @@ out:
 static void nbd_release(struct gendisk *disk, fmode_t mode)
 {
        struct nbd_device *nbd = disk->private_data;
+       struct block_device *bdev = bdget_disk(disk, 0);
+
+       if (test_bit(NBD_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
+                       bdev->bd_openers == 0)
+               nbd_disconnect_and_put(nbd);
+
        nbd_config_put(nbd);
        nbd_put(nbd);
 }
@@ -1705,6 +1713,10 @@ again:
                                &config->runtime_flags);
                        put_dev = true;
                }
+               if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
+                       set_bit(NBD_DISCONNECT_ON_CLOSE,
+                               &config->runtime_flags);
+               }
        }
 
        if (info->attrs[NBD_ATTR_SOCKETS]) {
@@ -1749,6 +1761,17 @@ out:
        return ret;
 }
 
+static void nbd_disconnect_and_put(struct nbd_device *nbd)
+{
+       mutex_lock(&nbd->config_lock);
+       nbd_disconnect(nbd);
+       nbd_clear_sock(nbd);
+       mutex_unlock(&nbd->config_lock);
+       if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
+                              &nbd->config->runtime_flags))
+               nbd_config_put(nbd);
+}
+
 static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
 {
        struct nbd_device *nbd;
@@ -1781,13 +1804,7 @@ static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
                nbd_put(nbd);
                return 0;
        }
-       mutex_lock(&nbd->config_lock);
-       nbd_disconnect(nbd);
-       nbd_clear_sock(nbd);
-       mutex_unlock(&nbd->config_lock);
-       if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
-                              &nbd->config->runtime_flags))
-               nbd_config_put(nbd);
+       nbd_disconnect_and_put(nbd);
        nbd_config_put(nbd);
        nbd_put(nbd);
        return 0;
@@ -1798,7 +1815,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
        struct nbd_device *nbd = NULL;
        struct nbd_config *config;
        int index;
-       int ret = -EINVAL;
+       int ret = 0;
        bool put_dev = false;
 
        if (!netlink_capable(skb, CAP_SYS_ADMIN))
@@ -1838,6 +1855,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
            !nbd->task_recv) {
                dev_err(nbd_to_dev(nbd),
                        "not configured, cannot reconfigure\n");
+               ret = -EINVAL;
                goto out;
        }
 
@@ -1862,6 +1880,14 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
                                               &config->runtime_flags))
                                refcount_inc(&nbd->refs);
                }
+
+               if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
+                       set_bit(NBD_DISCONNECT_ON_CLOSE,
+                                       &config->runtime_flags);
+               } else {
+                       clear_bit(NBD_DISCONNECT_ON_CLOSE,
+                                       &config->runtime_flags);
+               }
        }
 
        if (info->attrs[NBD_ATTR_SOCKETS]) {

diff --git a/include/uapi/linux/nbd.h b/include/uapi/linux/nbd.h
index 85a3fb6..20d6cc9 100644 (file)
--- a/include/uapi/linux/nbd.h
+++ b/include/uapi/linux/nbd.h
@@ -53,6 +53,9 @@ enum {
 /* These are client behavior specific flags. */
 #define NBD_CFLAG_DESTROY_ON_DISCONNECT        (1 << 0) /* delete the nbd device on
                                                    disconnect. */
+#define NBD_CFLAG_DISCONNECT_ON_CLOSE (1 << 1) /* disconnect the nbd device on
+                                               *  close by last opener.
+                                               */
 
 /* userspace doesn't need the nbd_device structure */