[PATCH net-next v2 4/7] mld: get rid of inet6_dev->mc_lock

[Taehee Yoo]

The purpose of mc_lock is to protect inet6_dev->mc_tomb.
But mc_tomb is already protected by RTNL and all functions,
which manipulate mc_tomb are called under RTNL.
So, mc_lock is not needed.
Furthermore, it is spinlock so the critical section is atomic.
In order to reduce atomic context, it should be removed.

Suggested-by: Cong Wang <xiyou.wangc...@gmail.com>
Signed-off-by: Taehee Yoo <ap420...@gmail.com>
---
v1 -> v2:
 - Separated from previous big one patch.

 include/net/if_inet6.h | 1 -
 net/ipv6/mcast.c       | 9 ---------
 2 files changed, 10 deletions(-)

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 5946b5d76f7b..4d9855be644c 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -167,7 +167,6 @@ struct inet6_dev {
 
        struct ifmcaddr6        *mc_list;
        struct ifmcaddr6        *mc_tomb;
-       spinlock_t              mc_lock;
 
        unsigned char           mc_qrv;         /* Query Robustness Variable */
        unsigned char           mc_gq_running;
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index ca8ca6faca4e..e80b78b1a8a7 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -748,10 +748,8 @@ static void mld_add_delrec(struct inet6_dev *idev, struct 
ifmcaddr6 *im)
        }
        spin_unlock_bh(&im->mca_lock);
 
-       spin_lock_bh(&idev->mc_lock);
        pmc->next = idev->mc_tomb;
        idev->mc_tomb = pmc;
-       spin_unlock_bh(&idev->mc_lock);
 }
 
 static void mld_del_delrec(struct inet6_dev *idev, struct ifmcaddr6 *im)
@@ -760,7 +758,6 @@ static void mld_del_delrec(struct inet6_dev *idev, struct 
ifmcaddr6 *im)
        struct ip6_sf_list *psf;
        struct in6_addr *pmca = &im->mca_addr;
 
-       spin_lock_bh(&idev->mc_lock);
        pmc_prev = NULL;
        for (pmc = idev->mc_tomb; pmc; pmc = pmc->next) {
                if (ipv6_addr_equal(&pmc->mca_addr, pmca))
@@ -773,7 +770,6 @@ static void mld_del_delrec(struct inet6_dev *idev, struct 
ifmcaddr6 *im)
                else
                        idev->mc_tomb = pmc->next;
        }
-       spin_unlock_bh(&idev->mc_lock);
 
        spin_lock_bh(&im->mca_lock);
        if (pmc) {
@@ -797,10 +793,8 @@ static void mld_clear_delrec(struct inet6_dev *idev)
 {
        struct ifmcaddr6 *pmc, *nextpmc;
 
-       spin_lock_bh(&idev->mc_lock);
        pmc = idev->mc_tomb;
        idev->mc_tomb = NULL;
-       spin_unlock_bh(&idev->mc_lock);
 
        for (; pmc; pmc = nextpmc) {
                nextpmc = pmc->next;
@@ -1919,7 +1913,6 @@ static void mld_send_cr(struct inet6_dev *idev)
        int type, dtype;
 
        read_lock_bh(&idev->lock);
-       spin_lock(&idev->mc_lock);
 
        /* deleted MCA's */
        pmc_prev = NULL;
@@ -1953,7 +1946,6 @@ static void mld_send_cr(struct inet6_dev *idev)
                } else
                        pmc_prev = pmc;
        }
-       spin_unlock(&idev->mc_lock);
 
        /* change recs */
        for (pmc = idev->mc_list; pmc; pmc = pmc->next) {
@@ -2615,7 +2607,6 @@ void ipv6_mc_up(struct inet6_dev *idev)
 void ipv6_mc_init_dev(struct inet6_dev *idev)
 {
        write_lock_bh(&idev->lock);
-       spin_lock_init(&idev->mc_lock);
        idev->mc_gq_running = 0;
        INIT_DELAYED_WORK(&idev->mc_gq_work, mld_gq_work);
        idev->mc_tomb = NULL;
-- 
2.17.1