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mld: convert ipv6_mc_socklist->sflist to RCU
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The sflist has been protected by rwlock so that the critical section
is atomic context.
In order to switch this context, changing locking is needed.
The sflist actually already protected by RTNL So if it's converted
to use RCU, its control path context can be switched to sleepable.

Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Taehee Yoo authored and David S. Miller committed Mar 26, 2021
1 parent cf2ce33 commit 882ba1f
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Showing 2 changed files with 24 additions and 32 deletions.
4 changes: 2 additions & 2 deletions include/net/if_inet6.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,7 @@ struct inet6_ifaddr {
struct ip6_sf_socklist {
unsigned int sl_max;
unsigned int sl_count;
struct rcu_head rcu;
struct in6_addr sl_addr[];
};

Expand All @@ -91,8 +92,7 @@ struct ipv6_mc_socklist {
int ifindex;
unsigned int sfmode; /* MCAST_{INCLUDE,EXCLUDE} */
struct ipv6_mc_socklist __rcu *next;
rwlock_t sflock;
struct ip6_sf_socklist *sflist;
struct ip6_sf_socklist __rcu *sflist;
struct rcu_head rcu;
};

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52 changes: 22 additions & 30 deletions net/ipv6/mcast.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -178,8 +178,7 @@ static int __ipv6_sock_mc_join(struct sock *sk, int ifindex,

mc_lst->ifindex = dev->ifindex;
mc_lst->sfmode = mode;
rwlock_init(&mc_lst->sflock);
mc_lst->sflist = NULL;
RCU_INIT_POINTER(mc_lst->sflist, NULL);

/*
* now add/increase the group membership on the device
Expand Down Expand Up @@ -335,7 +334,6 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
struct net *net = sock_net(sk);
int i, j, rv;
int leavegroup = 0;
int pmclocked = 0;
int err;

source = &((struct sockaddr_in6 *)&pgsr->gsr_source)->sin6_addr;
Expand Down Expand Up @@ -364,7 +362,7 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
goto done;
}
/* if a source filter was set, must be the same mode as before */
if (pmc->sflist) {
if (rcu_access_pointer(pmc->sflist)) {
if (pmc->sfmode != omode) {
err = -EINVAL;
goto done;
Expand All @@ -376,10 +374,7 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
pmc->sfmode = omode;
}

write_lock(&pmc->sflock);
pmclocked = 1;

psl = pmc->sflist;
psl = rtnl_dereference(pmc->sflist);
if (!add) {
if (!psl)
goto done; /* err = -EADDRNOTAVAIL */
Expand Down Expand Up @@ -429,9 +424,11 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
if (psl) {
for (i = 0; i < psl->sl_count; i++)
newpsl->sl_addr[i] = psl->sl_addr[i];
sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
atomic_sub(IP6_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc);
kfree_rcu(psl, rcu);
}
pmc->sflist = psl = newpsl;
psl = newpsl;
rcu_assign_pointer(pmc->sflist, psl);
}
rv = 1; /* > 0 for insert logic below if sl_count is 0 */
for (i = 0; i < psl->sl_count; i++) {
Expand All @@ -447,8 +444,6 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
/* update the interface list */
ip6_mc_add_src(idev, group, omode, 1, source, 1);
done:
if (pmclocked)
write_unlock(&pmc->sflock);
read_unlock_bh(&idev->lock);
rcu_read_unlock();
if (leavegroup)
Expand Down Expand Up @@ -526,17 +521,16 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf,
(void) ip6_mc_add_src(idev, group, gsf->gf_fmode, 0, NULL, 0);
}

write_lock(&pmc->sflock);
psl = pmc->sflist;
psl = rtnl_dereference(pmc->sflist);
if (psl) {
(void) ip6_mc_del_src(idev, group, pmc->sfmode,
psl->sl_count, psl->sl_addr, 0);
sock_kfree_s(sk, psl, IP6_SFLSIZE(psl->sl_max));
atomic_sub(IP6_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc);
kfree_rcu(psl, rcu);
} else
(void) ip6_mc_del_src(idev, group, pmc->sfmode, 0, NULL, 0);
pmc->sflist = newpsl;
rcu_assign_pointer(pmc->sflist, newpsl);
pmc->sfmode = gsf->gf_fmode;
write_unlock(&pmc->sflock);
err = 0;
done:
read_unlock_bh(&idev->lock);
Expand Down Expand Up @@ -585,16 +579,14 @@ int ip6_mc_msfget(struct sock *sk, struct group_filter *gsf,
if (!pmc) /* must have a prior join */
goto done;
gsf->gf_fmode = pmc->sfmode;
psl = pmc->sflist;
psl = rtnl_dereference(pmc->sflist);
count = psl ? psl->sl_count : 0;
read_unlock_bh(&idev->lock);
rcu_read_unlock();

copycount = count < gsf->gf_numsrc ? count : gsf->gf_numsrc;
gsf->gf_numsrc = count;
/* changes to psl require the socket lock, and a write lock
* on pmc->sflock. We have the socket lock so reading here is safe.
*/

for (i = 0; i < copycount; i++, p++) {
struct sockaddr_in6 *psin6;
struct sockaddr_storage ss;
Expand Down Expand Up @@ -630,8 +622,7 @@ bool inet6_mc_check(struct sock *sk, const struct in6_addr *mc_addr,
rcu_read_unlock();
return np->mc_all;
}
read_lock(&mc->sflock);
psl = mc->sflist;
psl = rcu_dereference(mc->sflist);
if (!psl) {
rv = mc->sfmode == MCAST_EXCLUDE;
} else {
Expand All @@ -646,7 +637,6 @@ bool inet6_mc_check(struct sock *sk, const struct in6_addr *mc_addr,
if (mc->sfmode == MCAST_EXCLUDE && i < psl->sl_count)
rv = false;
}
read_unlock(&mc->sflock);
rcu_read_unlock();

return rv;
Expand Down Expand Up @@ -2422,19 +2412,21 @@ static void igmp6_join_group(struct ifmcaddr6 *ma)
static int ip6_mc_leave_src(struct sock *sk, struct ipv6_mc_socklist *iml,
struct inet6_dev *idev)
{
struct ip6_sf_socklist *psl;
int err;

write_lock_bh(&iml->sflock);
if (!iml->sflist) {
psl = rtnl_dereference(iml->sflist);

if (!psl) {
/* any-source empty exclude case */
err = ip6_mc_del_src(idev, &iml->addr, iml->sfmode, 0, NULL, 0);
} else {
err = ip6_mc_del_src(idev, &iml->addr, iml->sfmode,
iml->sflist->sl_count, iml->sflist->sl_addr, 0);
sock_kfree_s(sk, iml->sflist, IP6_SFLSIZE(iml->sflist->sl_max));
iml->sflist = NULL;
psl->sl_count, psl->sl_addr, 0);
RCU_INIT_POINTER(iml->sflist, NULL);
atomic_sub(IP6_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc);
kfree_rcu(psl, rcu);
}
write_unlock_bh(&iml->sflock);
return err;
}

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