tap: convert a mutex to a spinlock

We are not allowed to block on the RCU reader side, so can't
just hold the mutex as before. As a quick fix, convert it to
a spinlock.

Fixes: d9f1f61c0801 ("tap: Extending tap device create/destroy APIs")
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Sainath Grandhi <sainath.grandhi@intel.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 9 deletions

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 9af3239d6ad5..3570c7576993 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -106,7 +106,7 @@ struct major_info {
         struct rcu_head rcu;
         dev_t major;
         struct idr minor_idr;
-        struct mutex minor_lock;
+        spinlock_t minor_lock;
         const char *device_name;
         struct list_head next;
 };
@@ -416,15 +416,15 @@ int tap_get_minor(dev_t major, struct tap_dev *tap)
                 goto unlock;
         }
 
-        mutex_lock(&tap_major->minor_lock);
-        retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_KERNEL);
+        spin_lock(&tap_major->minor_lock);
+        retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);
         if (retval >= 0) {
                 tap->minor = retval;
         } else if (retval == -ENOSPC) {
                 netdev_err(tap->dev, "Too many tap devices\n");
                 retval = -EINVAL;
         }
-        mutex_unlock(&tap_major->minor_lock);
+        spin_unlock(&tap_major->minor_lock);
 
 unlock:
         rcu_read_unlock();
@@ -442,12 +442,12 @@ void tap_free_minor(dev_t major, struct tap_dev *tap)
                 goto unlock;
         }
 
-        mutex_lock(&tap_major->minor_lock);
+        spin_lock(&tap_major->minor_lock);
         if (tap->minor) {
                 idr_remove(&tap_major->minor_idr, tap->minor);
                 tap->minor = 0;
         }
-        mutex_unlock(&tap_major->minor_lock);
+        spin_unlock(&tap_major->minor_lock);
 
 unlock:
         rcu_read_unlock();
@@ -467,13 +467,13 @@ static struct tap_dev *dev_get_by_tap_file(int major, int minor)
                 goto unlock;
         }
 
-        mutex_lock(&tap_major->minor_lock);
+        spin_lock(&tap_major->minor_lock);
         tap = idr_find(&tap_major->minor_idr, minor);
         if (tap) {
                 dev = tap->dev;
                 dev_hold(dev);
         }
-        mutex_unlock(&tap_major->minor_lock);
+        spin_unlock(&tap_major->minor_lock);
 
 unlock:
         rcu_read_unlock();
@@ -1244,7 +1244,7 @@ static int tap_list_add(dev_t major, const char *device_name)
         tap_major->major = MAJOR(major);
 
         idr_init(&tap_major->minor_idr);
-        mutex_init(&tap_major->minor_lock);
+        spin_lock_init(&tap_major->minor_lock);
 
         tap_major->device_name = device_name;