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flow: virtualize flow cache entry methods
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This allows to validate the cached object before returning it.
It also allows to destruct object properly, if the last reference
was held in flow cache. This is also a prepartion for caching
bundles in the flow cache.

In return for virtualizing the methods, we save on:
- not having to regenerate the whole flow cache on policy removal:
  each flow matching a killed policy gets refreshed as the getter
  function notices it smartly.
- we do not have to call flow_cache_flush from policy gc, since the
  flow cache now properly deletes the object if it had any references

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Timo Teräs authored and David S. Miller committed Apr 7, 2010
1 parent 8020eb8 commit fe1a5f0
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Showing 4 changed files with 163 additions and 102 deletions.
23 changes: 19 additions & 4 deletions include/net/flow.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,11 +86,26 @@ struct flowi {

struct net;
struct sock;
typedef int (*flow_resolve_t)(struct net *net, struct flowi *key, u16 family,
u8 dir, void **objp, atomic_t **obj_refp);
struct flow_cache_ops;

struct flow_cache_object {
const struct flow_cache_ops *ops;
};

struct flow_cache_ops {
struct flow_cache_object *(*get)(struct flow_cache_object *);
int (*check)(struct flow_cache_object *);
void (*delete)(struct flow_cache_object *);
};

typedef struct flow_cache_object *(*flow_resolve_t)(
struct net *net, struct flowi *key, u16 family,
u8 dir, struct flow_cache_object *oldobj, void *ctx);

extern struct flow_cache_object *flow_cache_lookup(
struct net *net, struct flowi *key, u16 family,
u8 dir, flow_resolve_t resolver, void *ctx);

extern void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family,
u8 dir, flow_resolve_t resolver);
extern void flow_cache_flush(void);
extern atomic_t flow_cache_genid;

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2 changes: 2 additions & 0 deletions include/net/xfrm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include <net/route.h>
#include <net/ipv6.h>
#include <net/ip6_fib.h>
#include <net/flow.h>

#include <linux/interrupt.h>

Expand Down Expand Up @@ -481,6 +482,7 @@ struct xfrm_policy {
atomic_t refcnt;
struct timer_list timer;

struct flow_cache_object flo;
u32 priority;
u32 index;
struct xfrm_mark mark;
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128 changes: 68 additions & 60 deletions net/core/flow.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,33 +26,32 @@
#include <linux/security.h>

struct flow_cache_entry {
struct flow_cache_entry *next;
u16 family;
u8 dir;
u32 genid;
struct flowi key;
void *object;
atomic_t *object_ref;
struct flow_cache_entry *next;
u16 family;
u8 dir;
u32 genid;
struct flowi key;
struct flow_cache_object *object;
};

struct flow_cache_percpu {
struct flow_cache_entry ** hash_table;
struct flow_cache_entry **hash_table;
int hash_count;
u32 hash_rnd;
int hash_rnd_recalc;
struct tasklet_struct flush_tasklet;
};

struct flow_flush_info {
struct flow_cache * cache;
struct flow_cache *cache;
atomic_t cpuleft;
struct completion completion;
};

struct flow_cache {
u32 hash_shift;
unsigned long order;
struct flow_cache_percpu * percpu;
struct flow_cache_percpu *percpu;
struct notifier_block hotcpu_notifier;
int low_watermark;
int high_watermark;
Expand All @@ -78,12 +77,21 @@ static void flow_cache_new_hashrnd(unsigned long arg)
add_timer(&fc->rnd_timer);
}

static int flow_entry_valid(struct flow_cache_entry *fle)
{
if (atomic_read(&flow_cache_genid) != fle->genid)
return 0;
if (fle->object && !fle->object->ops->check(fle->object))
return 0;
return 1;
}

static void flow_entry_kill(struct flow_cache *fc,
struct flow_cache_percpu *fcp,
struct flow_cache_entry *fle)
{
if (fle->object)
atomic_dec(fle->object_ref);
fle->object->ops->delete(fle->object);
kmem_cache_free(flow_cachep, fle);
fcp->hash_count--;
}
Expand All @@ -96,16 +104,18 @@ static void __flow_cache_shrink(struct flow_cache *fc,
int i;

for (i = 0; i < flow_cache_hash_size(fc); i++) {
int k = 0;
int saved = 0;

flp = &fcp->hash_table[i];
while ((fle = *flp) != NULL && k < shrink_to) {
k++;
flp = &fle->next;
}
while ((fle = *flp) != NULL) {
*flp = fle->next;
flow_entry_kill(fc, fcp, fle);
if (saved < shrink_to &&
flow_entry_valid(fle)) {
saved++;
flp = &fle->next;
} else {
*flp = fle->next;
flow_entry_kill(fc, fcp, fle);
}
}
}
}
Expand Down Expand Up @@ -166,46 +176,39 @@ static int flow_key_compare(struct flowi *key1, struct flowi *key2)
return 0;
}

void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
flow_resolve_t resolver)
struct flow_cache_object *
flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
flow_resolve_t resolver, void *ctx)
{
struct flow_cache *fc = &flow_cache_global;
struct flow_cache_percpu *fcp;
struct flow_cache_entry *fle, **head;
struct flow_cache_object *flo;
unsigned int hash;

local_bh_disable();
fcp = per_cpu_ptr(fc->percpu, smp_processor_id());

fle = NULL;
flo = NULL;
/* Packet really early in init? Making flow_cache_init a
* pre-smp initcall would solve this. --RR */
if (!fcp->hash_table)
goto nocache;

if (fcp->hash_rnd_recalc)
flow_new_hash_rnd(fc, fcp);
hash = flow_hash_code(fc, fcp, key);

hash = flow_hash_code(fc, fcp, key);
head = &fcp->hash_table[hash];
for (fle = *head; fle; fle = fle->next) {
if (fle->family == family &&
fle->dir == dir &&
flow_key_compare(key, &fle->key) == 0) {
if (fle->genid == atomic_read(&flow_cache_genid)) {
void *ret = fle->object;

if (ret)
atomic_inc(fle->object_ref);
local_bh_enable();

return ret;
}
flow_key_compare(key, &fle->key) == 0)
break;
}
}

if (!fle) {
if (unlikely(!fle)) {
if (fcp->hash_count > fc->high_watermark)
flow_cache_shrink(fc, fcp);

Expand All @@ -219,33 +222,39 @@ void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
fle->object = NULL;
fcp->hash_count++;
}
} else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
flo = fle->object;
if (!flo)
goto ret_object;
flo = flo->ops->get(flo);
if (flo)
goto ret_object;
} else if (fle->object) {
flo = fle->object;
flo->ops->delete(flo);
fle->object = NULL;
}

nocache:
{
int err;
void *obj;
atomic_t *obj_ref;

err = resolver(net, key, family, dir, &obj, &obj_ref);

if (fle && !err) {
fle->genid = atomic_read(&flow_cache_genid);

if (fle->object)
atomic_dec(fle->object_ref);

fle->object = obj;
fle->object_ref = obj_ref;
if (obj)
atomic_inc(fle->object_ref);
}
local_bh_enable();

if (err)
obj = ERR_PTR(err);
return obj;
flo = NULL;
if (fle) {
flo = fle->object;
fle->object = NULL;
}
flo = resolver(net, key, family, dir, flo, ctx);
if (fle) {
fle->genid = atomic_read(&flow_cache_genid);
if (!IS_ERR(flo))
fle->object = flo;
else
fle->genid--;
} else {
if (flo && !IS_ERR(flo))
flo->ops->delete(flo);
}
ret_object:
local_bh_enable();
return flo;
}

static void flow_cache_flush_tasklet(unsigned long data)
Expand All @@ -261,13 +270,12 @@ static void flow_cache_flush_tasklet(unsigned long data)

fle = fcp->hash_table[i];
for (; fle; fle = fle->next) {
unsigned genid = atomic_read(&flow_cache_genid);

if (!fle->object || fle->genid == genid)
if (flow_entry_valid(fle))
continue;

if (fle->object)
fle->object->ops->delete(fle->object);
fle->object = NULL;
atomic_dec(fle->object_ref);
}
}

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