nbd: refactor device search and allocation in nbd_genl_connect

Use idr_for_each_entry instead of the awkward callback to find an
existing device for the index == -1 case, and de-duplicate the device
allocation if no existing device was found.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-6-hch@lst.de
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index a81b95c..8c0e334 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1767,18 +1767,6 @@ out:
        return ERR_PTR(err);
 }
 
-static int find_free_cb(int id, void *ptr, void *data)
-{
-       struct nbd_device *nbd = ptr;
-       struct nbd_device **found = data;
-
-       if (!refcount_read(&nbd->config_refs)) {
-               *found = nbd;
-               return 1;
-       }
-       return 0;
-}
-
 /* Netlink interface. */
 static const struct nla_policy nbd_attr_policy[NBD_ATTR_MAX + 1] = {
        [NBD_ATTR_INDEX]                =       { .type = NLA_U32 },
@@ -1848,31 +1836,26 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 again:
        mutex_lock(&nbd_index_mutex);
        if (index == -1) {
-               ret = idr_for_each(&nbd_index_idr, &find_free_cb, &nbd);
-               if (ret == 0) {
-                       nbd = nbd_dev_add(-1);
-                       if (IS_ERR(nbd)) {
-                               mutex_unlock(&nbd_index_mutex);
-                               printk(KERN_ERR "nbd: failed to add new device\n");
-                               return PTR_ERR(nbd);
+               struct nbd_device *tmp;
+               int id;
+
+               idr_for_each_entry(&nbd_index_idr, tmp, id) {
+                       if (!refcount_read(&tmp->config_refs)) {
+                               nbd = tmp;
+                               break;
                        }
                }
        } else {
                nbd = idr_find(&nbd_index_idr, index);
-               if (!nbd) {
-                       nbd = nbd_dev_add(index);
-                       if (IS_ERR(nbd)) {
-                               mutex_unlock(&nbd_index_mutex);
-                               printk(KERN_ERR "nbd: failed to add new device\n");
-                               return PTR_ERR(nbd);
-                       }
-               }
        }
+
        if (!nbd) {
-               printk(KERN_ERR "nbd: couldn't find device at index %d\n",
-                      index);
-               mutex_unlock(&nbd_index_mutex);
-               return -EINVAL;
+               nbd = nbd_dev_add(index);
+               if (IS_ERR(nbd)) {
+                       mutex_unlock(&nbd_index_mutex);
+                       pr_err("nbd: failed to add new device\n");
+                       return PTR_ERR(nbd);
+               }
        }
 
        if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&