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ipmr: convert mrt_lock to a spinlock

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mrt_lock is only held in write mode, from process context only.

We can switch to a mere spinlock, and avoid blocking BH.

Also, vif_dev_read() is always called under standard rcu_read_lock().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2022-06-23 04:34:48 +00:00 committed by David S. Miller
parent b96ef16d2f
commit 3f55211ecf
1 changed files with 9 additions and 10 deletions
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19
net/ipv4/ipmr.c
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@ -77,12 +77,11 @@ struct ipmr_result {
* Note that the changes are semaphored via rtnl_lock.
*/
static DEFINE_RWLOCK(mrt_lock);
static DEFINE_SPINLOCK(mrt_lock);
static struct net_device *vif_dev_read(const struct vif_device *vif)
{
return rcu_dereference_check(vif->dev,
lockdep_is_held(&mrt_lock));
return rcu_dereference(vif->dev);
}
/* Multicast router control variables */
@ -664,7 +663,7 @@ static int vif_delete(struct mr_table *mrt, int vifi, int notify,
if (!dev)
return -EADDRNOTAVAIL;
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_DEL, v, dev,
vifi, mrt->id);
RCU_INIT_POINTER(v->dev, NULL);
@ -683,7 +682,7 @@ static int vif_delete(struct mr_table *mrt, int vifi, int notify,
WRITE_ONCE(mrt->maxvif, tmp + 1);
}
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
dev_set_allmulti(dev, -1);
@ -785,7 +784,7 @@ out:
spin_unlock(&mfc_unres_lock);
}
/* Fill oifs list. It is called under write locked mrt_lock. */
/* Fill oifs list. It is called under locked mrt_lock. */
static void ipmr_update_thresholds(struct mr_table *mrt, struct mr_mfc *cache,
unsigned char *ttls)
{
@ -897,7 +896,7 @@ static int vif_add(struct net *net, struct mr_table *mrt,
v->remote = vifc->vifc_rmt_addr.s_addr;
/* And finish update writing critical data */
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
rcu_assign_pointer(v->dev, dev);
netdev_tracker_alloc(dev, &v->dev_tracker, GFP_ATOMIC);
if (v->flags & VIFF_REGISTER) {
@ -906,7 +905,7 @@ static int vif_add(struct net *net, struct mr_table *mrt,
}
if (vifi+1 > mrt->maxvif)
WRITE_ONCE(mrt->maxvif, vifi + 1);
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD, v, dev,
vifi, mrt->id);
return 0;
@ -1211,12 +1210,12 @@ static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,
mfc->mfcc_mcastgrp.s_addr, parent);
rcu_read_unlock();
if (c) {
write_lock_bh(&mrt_lock);
spin_lock(&mrt_lock);
c->_c.mfc_parent = mfc->mfcc_parent;
ipmr_update_thresholds(mrt, &c->_c, mfc->mfcc_ttls);
if (!mrtsock)
c->_c.mfc_flags |= MFC_STATIC;
write_unlock_bh(&mrt_lock);
spin_unlock(&mrt_lock);
call_ipmr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_REPLACE, c,
mrt->id);
mroute_netlink_event(mrt, c, RTM_NEWROUTE);