[PATCH net-next v3 4/7] mld: convert ip6_sf_list to RCU

Taehee Yoo
2021-03-25T16:18:09Z

The ip6_sf_list has been protected by mca_lock(spin_lock) so that the
critical section is atomic context. In order to switch this context,
changing locking is needed. The ip6_sf_list actually already protected
by RTNL So if it's converted to use RCU, its control path context can
be switched to sleepable.
But It doesn't remove mca_lock yet because ifmcaddr6 isn't converted
to RCU yet. So, It's not fully converted to the sleepable context.

Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
v2 -> v3:
- Fix sparse warnings because of rcu annotation
v1 -> v2:
- Separated from previous big one patch.

include/net/if_inet6.h | 7 +-
net/ipv6/mcast.c | 200 ++++++++++++++++++++++++++---------------
2 files changed, 130 insertions(+), 77 deletions(-)

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 062294aeeb6d..7875a3208426 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -97,12 +97,13 @@ struct ipv6_mc_socklist {
};

struct ip6_sf_list {
- struct ip6_sf_list *sf_next;
+ struct ip6_sf_list __rcu *sf_next;
struct in6_addr sf_addr;
unsigned long sf_count[2]; /* include/exclude counts */
unsigned char sf_gsresp; /* include in g & s response? */
unsigned char sf_oldin; /* change state */
unsigned char sf_crcount; /* retrans. left to send */
+ struct rcu_head rcu;
};

#define MAF_TIMER_RUNNING 0x01
@@ -115,8 +116,8 @@ struct ifmcaddr6 {
struct in6_addr mca_addr;
struct inet6_dev *idev;
struct ifmcaddr6 *next;
- struct ip6_sf_list *mca_sources;
- struct ip6_sf_list *mca_tomb;
+ struct ip6_sf_list __rcu *mca_sources;
+ struct ip6_sf_list __rcu *mca_tomb;
unsigned int mca_sfmode;
unsigned char mca_crcount;
unsigned long mca_sfcount[2];
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 9da55d23a13c..bc0fb4815c97 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -113,10 +113,25 @@ int sysctl_mld_qrv __read_mostly = MLD_QRV_DEFAULT;
*/

#define for_each_pmc_rcu(np, pmc) \
- for (pmc = rcu_dereference(np->ipv6_mc_list); \
- pmc != NULL; \
+ for (pmc = rcu_dereference((np)->ipv6_mc_list); \
+ pmc; \
pmc = rcu_dereference(pmc->next))

+#define for_each_psf_rtnl(mc, psf) \
+ for (psf = rtnl_dereference((mc)->mca_sources); \
+ psf; \
+ psf = rtnl_dereference(psf->sf_next))
+
+#define for_each_psf_rcu(mc, psf) \
+ for (psf = rcu_dereference((mc)->mca_sources); \
+ psf; \
+ psf = rcu_dereference(psf->sf_next))
+
+#define for_each_psf_tomb(mc, psf) \
+ for (psf = rtnl_dereference((mc)->mca_tomb); \
+ psf; \
+ psf = rtnl_dereference(psf->sf_next))
+
static int unsolicited_report_interval(struct inet6_dev *idev)
{
int iv;
@@ -734,10 +749,14 @@ static void mld_add_delrec(struct inet6_dev *idev, struct ifmcaddr6 *im)
if (pmc->mca_sfmode == MCAST_INCLUDE) {
struct ip6_sf_list *psf;

- pmc->mca_tomb = im->mca_tomb;
- pmc->mca_sources = im->mca_sources;
- im->mca_tomb = im->mca_sources = NULL;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next)
+ rcu_assign_pointer(pmc->mca_tomb,
+ rtnl_dereference(im->mca_tomb));
+ rcu_assign_pointer(pmc->mca_sources,
+ rtnl_dereference(im->mca_sources));
+ RCU_INIT_POINTER(im->mca_tomb, NULL);
+ RCU_INIT_POINTER(im->mca_sources, NULL);
+
+ for_each_psf_rtnl(pmc, psf)
psf->sf_crcount = pmc->mca_crcount;
}
spin_unlock_bh(&im->mca_lock);
@@ -748,9 +767,9 @@ static void mld_add_delrec(struct inet6_dev *idev, struct ifmcaddr6 *im)

static void mld_del_delrec(struct inet6_dev *idev, struct ifmcaddr6 *im)
{
- struct ifmcaddr6 *pmc, *pmc_prev;
- struct ip6_sf_list *psf;
+ struct ip6_sf_list *psf, *sources, *tomb;
struct in6_addr *pmca = &im->mca_addr;
+ struct ifmcaddr6 *pmc, *pmc_prev;

pmc_prev = NULL;
for (pmc = idev->mc_tomb; pmc; pmc = pmc->next) {
@@ -769,9 +788,16 @@ static void mld_del_delrec(struct inet6_dev *idev, struct ifmcaddr6 *im)
if (pmc) {
im->idev = pmc->idev;
if (im->mca_sfmode == MCAST_INCLUDE) {
- swap(im->mca_tomb, pmc->mca_tomb);
- swap(im->mca_sources, pmc->mca_sources);
- for (psf = im->mca_sources; psf; psf = psf->sf_next)
+ tomb = rcu_replace_pointer(im->mca_tomb,
+ rtnl_dereference(pmc->mca_tomb),
+ lockdep_rtnl_is_held());
+ rcu_assign_pointer(pmc->mca_tomb, tomb);
+
+ sources = rcu_replace_pointer(im->mca_sources,
+ rtnl_dereference(pmc->mca_sources),
+ lockdep_rtnl_is_held());
+ rcu_assign_pointer(pmc->mca_sources, sources);
+ for_each_psf_rtnl(im, psf)
psf->sf_crcount = idev->mc_qrv;
} else {
im->mca_crcount = idev->mc_qrv;
@@ -803,12 +829,12 @@ static void mld_clear_delrec(struct inet6_dev *idev)
struct ip6_sf_list *psf, *psf_next;

spin_lock_bh(&pmc->mca_lock);
- psf = pmc->mca_tomb;
- pmc->mca_tomb = NULL;
+ psf = rtnl_dereference(pmc->mca_tomb);
+ RCU_INIT_POINTER(pmc->mca_tomb, NULL);
spin_unlock_bh(&pmc->mca_lock);
for (; psf; psf = psf_next) {
- psf_next = psf->sf_next;
- kfree(psf);
+ psf_next = rtnl_dereference(psf->sf_next);
+ kfree_rcu(psf, rcu);
}
}
read_unlock_bh(&idev->lock);
@@ -990,7 +1016,7 @@ bool ipv6_chk_mcast_addr(struct net_device *dev, const struct in6_addr *group,
struct ip6_sf_list *psf;

spin_lock_bh(&mc->mca_lock);
- for (psf = mc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rcu(mc, psf) {
if (ipv6_addr_equal(&psf->sf_addr, src_addr))
break;
}
@@ -1089,7 +1115,7 @@ static bool mld_xmarksources(struct ifmcaddr6 *pmc, int nsrcs,
int i, scount;

scount = 0;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rcu(pmc, psf) {
if (scount == nsrcs)
break;
for (i = 0; i < nsrcs; i++) {
@@ -1122,7 +1148,7 @@ static bool mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
/* mark INCLUDE-mode sources */

scount = 0;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rcu(pmc, psf) {
if (scount == nsrcs)
break;
for (i = 0; i < nsrcs; i++) {
@@ -1532,7 +1558,7 @@ mld_scount(struct ifmcaddr6 *pmc, int type, int gdeleted, int sdeleted)
struct ip6_sf_list *psf;
int scount = 0;

- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rtnl(pmc, psf) {
if (!is_in(pmc, psf, type, gdeleted, sdeleted))
continue;
scount++;
@@ -1707,14 +1733,16 @@ static struct sk_buff *add_grhead(struct sk_buff *skb, struct ifmcaddr6 *pmc,
#define AVAILABLE(skb) ((skb) ? skb_availroom(skb) : 0)

static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
- int type, int gdeleted, int sdeleted, int crsend)
+ int type, int gdeleted, int sdeleted,
+ int crsend)
{
+ struct ip6_sf_list *psf, *psf_prev, *psf_next;
+ int scount, stotal, first, isquery, truncate;
+ struct ip6_sf_list __rcu **psf_list;
struct inet6_dev *idev = pmc->idev;
struct net_device *dev = idev->dev;
- struct mld2_report *pmr;
struct mld2_grec *pgr = NULL;
- struct ip6_sf_list *psf, *psf_next, *psf_prev, **psf_list;
- int scount, stotal, first, isquery, truncate;
+ struct mld2_report *pmr;
unsigned int mtu;

if (pmc->mca_flags & MAF_NOREPORT)
@@ -1733,7 +1761,7 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,

psf_list = sdeleted ? &pmc->mca_tomb : &pmc->mca_sources;

- if (!*psf_list)
+ if (!rcu_access_pointer(*psf_list))
goto empty_source;

pmr = skb ? (struct mld2_report *)skb_transport_header(skb) : NULL;
@@ -1749,10 +1777,12 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
}
first = 1;
psf_prev = NULL;
- for (psf = *psf_list; psf; psf = psf_next) {
+ for (psf = rtnl_dereference(*psf_list);
+ psf;
+ psf = psf_next) {
struct in6_addr *psrc;

- psf_next = psf->sf_next;
+ psf_next = rtnl_dereference(psf->sf_next);

if (!is_in(pmc, psf, type, gdeleted, sdeleted) && !crsend) {
psf_prev = psf;
@@ -1799,10 +1829,12 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
psf->sf_crcount--;
if ((sdeleted || gdeleted) && psf->sf_crcount == 0) {
if (psf_prev)
- psf_prev->sf_next = psf->sf_next;
+ rcu_assign_pointer(psf_prev->sf_next,
+ rtnl_dereference(psf->sf_next));
else
- *psf_list = psf->sf_next;
- kfree(psf);
+ rcu_assign_pointer(*psf_list,
+ rtnl_dereference(psf->sf_next));
+ kfree_rcu(psf, rcu);
continue;
}
}
@@ -1866,21 +1898,26 @@ static void mld_send_report(struct inet6_dev *idev, struct ifmcaddr6 *pmc)
/*
* remove zero-count source records from a source filter list
*/
-static void mld_clear_zeros(struct ip6_sf_list **ppsf)
+static void mld_clear_zeros(struct ip6_sf_list __rcu **ppsf)
{
struct ip6_sf_list *psf_prev, *psf_next, *psf;

psf_prev = NULL;
- for (psf = *ppsf; psf; psf = psf_next) {
- psf_next = psf->sf_next;
+ for (psf = rtnl_dereference(*ppsf);
+ psf;
+ psf = psf_next) {
+ psf_next = rtnl_dereference(psf->sf_next);
if (psf->sf_crcount == 0) {
if (psf_prev)
- psf_prev->sf_next = psf->sf_next;
+ rcu_assign_pointer(psf_prev->sf_next,
+ rtnl_dereference(psf->sf_next));
else
- *ppsf = psf->sf_next;
- kfree(psf);
- } else
+ rcu_assign_pointer(*ppsf,
+ rtnl_dereference(psf->sf_next));
+ kfree_rcu(psf, rcu);
+ } else {
psf_prev = psf;
+ }
}
}

@@ -1913,8 +1950,9 @@ static void mld_send_cr(struct inet6_dev *idev)
mld_clear_zeros(&pmc->mca_sources);
}
}
- if (pmc->mca_crcount == 0 && !pmc->mca_tomb &&
- !pmc->mca_sources) {
+ if (pmc->mca_crcount == 0 &&
+ !rcu_access_pointer(pmc->mca_tomb) &&
+ !rcu_access_pointer(pmc->mca_sources)) {
if (pmc_prev)
pmc_prev->next = pmc_next;
else
@@ -2111,7 +2149,7 @@ static int ip6_mc_del1_src(struct ifmcaddr6 *pmc, int sfmode,
int rv = 0;

psf_prev = NULL;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rtnl(pmc, psf) {
if (ipv6_addr_equal(&psf->sf_addr, psfsrc))
break;
psf_prev = psf;
@@ -2126,17 +2164,22 @@ static int ip6_mc_del1_src(struct ifmcaddr6 *pmc, int sfmode,

/* no more filters for this source */
if (psf_prev)
- psf_prev->sf_next = psf->sf_next;
+ rcu_assign_pointer(psf_prev->sf_next,
+ rtnl_dereference(psf->sf_next));
else
- pmc->mca_sources = psf->sf_next;
+ rcu_assign_pointer(pmc->mca_sources,
+ rtnl_dereference(psf->sf_next));
+
if (psf->sf_oldin && !(pmc->mca_flags & MAF_NOREPORT) &&
!mld_in_v1_mode(idev)) {
psf->sf_crcount = idev->mc_qrv;
- psf->sf_next = pmc->mca_tomb;
- pmc->mca_tomb = psf;
+ rcu_assign_pointer(psf->sf_next,
+ rtnl_dereference(pmc->mca_tomb));
+ rcu_assign_pointer(pmc->mca_tomb, psf);
rv = 1;
- } else
- kfree(psf);
+ } else {
+ kfree_rcu(psf, rcu);
+ }
}
return rv;
}
@@ -2188,7 +2231,7 @@ static int ip6_mc_del_src(struct inet6_dev *idev, const struct in6_addr *pmca,
pmc->mca_sfmode = MCAST_INCLUDE;
pmc->mca_crcount = idev->mc_qrv;
idev->mc_ifc_count = pmc->mca_crcount;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next)
+ for_each_psf_rtnl(pmc, psf)
psf->sf_crcount = 0;
mld_ifc_event(pmc->idev);
} else if (sf_setstate(pmc) || changerec)
@@ -2207,7 +2250,7 @@ static int ip6_mc_add1_src(struct ifmcaddr6 *pmc, int sfmode,
struct ip6_sf_list *psf, *psf_prev;

psf_prev = NULL;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rtnl(pmc, psf) {
if (ipv6_addr_equal(&psf->sf_addr, psfsrc))
break;
psf_prev = psf;
@@ -2219,9 +2262,10 @@ static int ip6_mc_add1_src(struct ifmcaddr6 *pmc, int sfmode,

psf->sf_addr = *psfsrc;
if (psf_prev) {
- psf_prev->sf_next = psf;
- } else
- pmc->mca_sources = psf;
+ rcu_assign_pointer(psf_prev->sf_next, psf);
+ } else {
+ rcu_assign_pointer(pmc->mca_sources, psf);
+ }
}
psf->sf_count[sfmode]++;
return 0;
@@ -2232,13 +2276,15 @@ static void sf_markstate(struct ifmcaddr6 *pmc)
struct ip6_sf_list *psf;
int mca_xcount = pmc->mca_sfcount[MCAST_EXCLUDE];

- for (psf = pmc->mca_sources; psf; psf = psf->sf_next)
+ for_each_psf_rtnl(pmc, psf) {
if (pmc->mca_sfcount[MCAST_EXCLUDE]) {
psf->sf_oldin = mca_xcount ==
psf->sf_count[MCAST_EXCLUDE] &&
!psf->sf_count[MCAST_INCLUDE];
- } else
+ } else {
psf->sf_oldin = psf->sf_count[MCAST_INCLUDE] != 0;
+ }
+ }
}

static int sf_setstate(struct ifmcaddr6 *pmc)
@@ -2249,7 +2295,7 @@ static int sf_setstate(struct ifmcaddr6 *pmc)
int new_in, rv;

rv = 0;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next) {
+ for_each_psf_rtnl(pmc, psf) {
if (pmc->mca_sfcount[MCAST_EXCLUDE]) {
new_in = mca_xcount == psf->sf_count[MCAST_EXCLUDE] &&
!psf->sf_count[MCAST_INCLUDE];
@@ -2259,8 +2305,7 @@ static int sf_setstate(struct ifmcaddr6 *pmc)
if (!psf->sf_oldin) {
struct ip6_sf_list *prev = NULL;

- for (dpsf = pmc->mca_tomb; dpsf;
- dpsf = dpsf->sf_next) {
+ for_each_psf_tomb(pmc, dpsf) {
if (ipv6_addr_equal(&dpsf->sf_addr,
&psf->sf_addr))
break;
@@ -2268,10 +2313,12 @@ static int sf_setstate(struct ifmcaddr6 *pmc)
}
if (dpsf) {
if (prev)
- prev->sf_next = dpsf->sf_next;
+ rcu_assign_pointer(prev->sf_next,
+ rtnl_dereference(dpsf->sf_next));
else
- pmc->mca_tomb = dpsf->sf_next;
- kfree(dpsf);
+ rcu_assign_pointer(pmc->mca_tomb,
+ rtnl_dereference(dpsf->sf_next));
+ kfree_rcu(dpsf, rcu);
}
psf->sf_crcount = qrv;
rv++;
@@ -2282,7 +2329,8 @@ static int sf_setstate(struct ifmcaddr6 *pmc)
* add or update "delete" records if an active filter
* is now inactive
*/
- for (dpsf = pmc->mca_tomb; dpsf; dpsf = dpsf->sf_next)
+
+ for_each_psf_tomb(pmc, dpsf)
if (ipv6_addr_equal(&dpsf->sf_addr,
&psf->sf_addr))
break;
@@ -2291,9 +2339,9 @@ static int sf_setstate(struct ifmcaddr6 *pmc)
if (!dpsf)
continue;
*dpsf = *psf;
- /* pmc->mca_lock held by callers */
- dpsf->sf_next = pmc->mca_tomb;
- pmc->mca_tomb = dpsf;
+ rcu_assign_pointer(dpsf->sf_next,
+ rtnl_dereference(pmc->mca_tomb));
+ rcu_assign_pointer(pmc->mca_tomb, dpsf);
}
dpsf->sf_crcount = qrv;
rv++;
@@ -2356,7 +2404,7 @@ static int ip6_mc_add_src(struct inet6_dev *idev, const struct in6_addr *pmca,

pmc->mca_crcount = idev->mc_qrv;
idev->mc_ifc_count = pmc->mca_crcount;
- for (psf = pmc->mca_sources; psf; psf = psf->sf_next)
+ for_each_psf_rtnl(pmc, psf)
psf->sf_crcount = 0;
mld_ifc_event(idev);
} else if (sf_setstate(pmc))
@@ -2370,16 +2418,20 @@ static void ip6_mc_clear_src(struct ifmcaddr6 *pmc)
{
struct ip6_sf_list *psf, *nextpsf;

- for (psf = pmc->mca_tomb; psf; psf = nextpsf) {
- nextpsf = psf->sf_next;
- kfree(psf);
+ for (psf = rtnl_dereference(pmc->mca_tomb);
+ psf;
+ psf = nextpsf) {
+ nextpsf = rtnl_dereference(psf->sf_next);
+ kfree_rcu(psf, rcu);
}
- pmc->mca_tomb = NULL;
- for (psf = pmc->mca_sources; psf; psf = nextpsf) {
- nextpsf = psf->sf_next;
- kfree(psf);
+ RCU_INIT_POINTER(pmc->mca_tomb, NULL);
+ for (psf = rtnl_dereference(pmc->mca_sources);
+ psf;
+ psf = nextpsf) {
+ nextpsf = rtnl_dereference(psf->sf_next);
+ kfree_rcu(psf, rcu);
}
- pmc->mca_sources = NULL;
+ RCU_INIT_POINTER(pmc->mca_sources, NULL);
pmc->mca_sfmode = MCAST_EXCLUDE;
pmc->mca_sfcount[MCAST_INCLUDE] = 0;
pmc->mca_sfcount[MCAST_EXCLUDE] = 1;
@@ -2789,7 +2841,7 @@ static inline struct ip6_sf_list *igmp6_mcf_get_first(struct seq_file *seq)
im = idev->mc_list;
if (likely(im)) {
spin_lock_bh(&im->mca_lock);
- psf = im->mca_sources;
+ psf = rcu_dereference(im->mca_sources);
if (likely(psf)) {
state->im = im;
state->idev = idev;
@@ -2806,7 +2858,7 @@ static struct ip6_sf_list *igmp6_mcf_get_next(struct seq_file *seq, struct ip6_s
{
struct igmp6_mcf_iter_state *state = igmp6_mcf_seq_private(seq);

- psf = psf->sf_next;
+ psf = rcu_dereference(psf->sf_next);
while (!psf) {
spin_unlock_bh(&state->im->mca_lock);
state->im = state->im->next;
@@ -2828,7 +2880,7 @@ static struct ip6_sf_list *igmp6_mcf_get_next(struct seq_file *seq, struct ip6_s
if (!state->im)
break;
spin_lock_bh(&state->im->mca_lock);
- psf = state->im->mca_sources;
+ psf = rcu_dereference(state->im->mca_sources);
}
out:
return psf;
--
2.17.1