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bpf: Use bpf_mem_cache_alloc/free for bpf_local_storage

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This patch uses bpf_mem_cache_alloc/free for allocating and freeing
bpf_local_storage for task and cgroup storage.

The changes are similar to the previous patch. A few things that
worth to mention for bpf_local_storage:

The local_storage is freed when the last selem is deleted.
Before deleting a selem from local_storage, it needs to retrieve the
local_storage->smap because the bpf_selem_unlink_storage_nolock()
may have set it to NULL. Note that local_storage->smap may have
already been NULL when the selem created this local_storage has
been removed. In this case, call_rcu will be used to free the
local_storage.
Also, the bpf_ma (true or false) value is needed before calling
bpf_local_storage_free(). The bpf_ma can either be obtained from
the local_storage->smap (if available) or any of its selem's smap.
A new helper check_storage_bpf_ma() is added to obtain
bpf_ma for a deleting bpf_local_storage.

When bpf_local_storage_alloc getting a reused memory, all
fields are either in the correct values or will be initialized.
'cache[]' must already be all NULLs. 'list' must be empty.
Others will be initialized.

Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20230322215246.1675516-4-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Martin KaFai Lau 2023-03-22 14:52:44 -07:00 committed by Alexei Starovoitov
parent 08a7ce384e
commit 6ae9d5e99e
2 changed files with 117 additions and 16 deletions
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1
include/linux/bpf_local_storage.h
View file

@ -57,6 +57,7 @@ struct bpf_local_storage_map {
u16 elem_size;
u16 cache_idx;
struct bpf_mem_alloc selem_ma;
struct bpf_mem_alloc storage_ma;
bool bpf_ma;
};

132
kernel/bpf/bpf_local_storage.c
View file

@ -111,33 +111,74 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
return NULL;
}
/* rcu tasks trace callback for bpf_ma == false */
static void __bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
{
struct bpf_local_storage *local_storage;
/* If RCU Tasks Trace grace period implies RCU grace period, do
* kfree(), else do kfree_rcu().
*/
local_storage = container_of(rcu, struct bpf_local_storage, rcu);
if (rcu_trace_implies_rcu_gp())
kfree(local_storage);
else
kfree_rcu(local_storage, rcu);
}
static void bpf_local_storage_free_rcu(struct rcu_head *rcu)
{
struct bpf_local_storage *local_storage;
local_storage = container_of(rcu, struct bpf_local_storage, rcu);
kfree(local_storage);
bpf_mem_cache_raw_free(local_storage);
}
static void bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
{
/* If RCU Tasks Trace grace period implies RCU grace period, do
* kfree(), else do kfree_rcu().
*/
if (rcu_trace_implies_rcu_gp())
bpf_local_storage_free_rcu(rcu);
else
call_rcu(rcu, bpf_local_storage_free_rcu);
}
static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
bool reuse_now)
/* Handle bpf_ma == false */
static void __bpf_local_storage_free(struct bpf_local_storage *local_storage,
bool vanilla_rcu)
{
if (!reuse_now)
if (vanilla_rcu)
kfree_rcu(local_storage, rcu);
else
call_rcu_tasks_trace(&local_storage->rcu,
__bpf_local_storage_free_trace_rcu);
}
static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
struct bpf_local_storage_map *smap,
bool bpf_ma, bool reuse_now)
{
if (!bpf_ma) {
__bpf_local_storage_free(local_storage, reuse_now);
return;
}
if (!reuse_now) {
call_rcu_tasks_trace(&local_storage->rcu,
bpf_local_storage_free_trace_rcu);
else
return;
}
if (smap) {
migrate_disable();
bpf_mem_cache_free(&smap->storage_ma, local_storage);
migrate_enable();
} else {
/* smap could be NULL if the selem that triggered
* this 'local_storage' creation had been long gone.
* In this case, directly do call_rcu().
*/
call_rcu(&local_storage->rcu, bpf_local_storage_free_rcu);
}
}
/* rcu tasks trace callback for bpf_ma == false */
@ -260,11 +301,47 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
return free_local_storage;
}
static bool check_storage_bpf_ma(struct bpf_local_storage *local_storage,
struct bpf_local_storage_map *storage_smap,
struct bpf_local_storage_elem *selem)
{
struct bpf_local_storage_map *selem_smap;
/* local_storage->smap may be NULL. If it is, get the bpf_ma
* from any selem in the local_storage->list. The bpf_ma of all
* local_storage and selem should have the same value
* for the same map type.
*
* If the local_storage->list is already empty, the caller will not
* care about the bpf_ma value also because the caller is not
* responsibile to free the local_storage.
*/
if (storage_smap)
return storage_smap->bpf_ma;
if (!selem) {
struct hlist_node *n;
n = rcu_dereference_check(hlist_first_rcu(&local_storage->list),
bpf_rcu_lock_held());
if (!n)
return false;
selem = hlist_entry(n, struct bpf_local_storage_elem, snode);
}
selem_smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
return selem_smap->bpf_ma;
}
static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
bool reuse_now)
{
struct bpf_local_storage_map *storage_smap;
struct bpf_local_storage *local_storage;
bool free_local_storage = false;
bool bpf_ma, free_local_storage = false;
unsigned long flags;
if (unlikely(!selem_linked_to_storage_lockless(selem)))
@ -273,6 +350,10 @@ static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
local_storage = rcu_dereference_check(selem->local_storage,
bpf_rcu_lock_held());
storage_smap = rcu_dereference_check(local_storage->smap,
bpf_rcu_lock_held());
bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem);
raw_spin_lock_irqsave(&local_storage->lock, flags);
if (likely(selem_linked_to_storage(selem)))
free_local_storage = bpf_selem_unlink_storage_nolock(
@ -280,7 +361,7 @@ static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (free_local_storage)
bpf_local_storage_free(local_storage, reuse_now);
bpf_local_storage_free(local_storage, storage_smap, bpf_ma, reuse_now);
}
void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
@ -400,8 +481,15 @@ int bpf_local_storage_alloc(void *owner,
if (err)
return err;
storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
gfp_flags | __GFP_NOWARN);
if (smap->bpf_ma) {
migrate_disable();
storage = bpf_mem_cache_alloc_flags(&smap->storage_ma, gfp_flags);
migrate_enable();
} else {
storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
gfp_flags | __GFP_NOWARN);
}
if (!storage) {
err = -ENOMEM;
goto uncharge;
@ -447,7 +535,7 @@ int bpf_local_storage_alloc(void *owner,
return 0;
uncharge:
bpf_local_storage_free(storage, true);
bpf_local_storage_free(storage, smap, smap->bpf_ma, true);
mem_uncharge(smap, owner, sizeof(*storage));
return err;
}
@ -660,11 +748,15 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map,
void bpf_local_storage_destroy(struct bpf_local_storage *local_storage)
{
struct bpf_local_storage_map *storage_smap;
struct bpf_local_storage_elem *selem;
bool free_storage = false;
bool bpf_ma, free_storage = false;
struct hlist_node *n;
unsigned long flags;
storage_smap = rcu_dereference_check(local_storage->smap, bpf_rcu_lock_held());
bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, NULL);
/* Neither the bpf_prog nor the bpf_map's syscall
* could be modifying the local_storage->list now.
* Thus, no elem can be added to or deleted from the
@ -692,7 +784,7 @@ void bpf_local_storage_destroy(struct bpf_local_storage *local_storage)
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (free_storage)
bpf_local_storage_free(local_storage, true);
bpf_local_storage_free(local_storage, storage_smap, bpf_ma, true);
}
u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map)
@ -755,6 +847,12 @@ bpf_local_storage_map_alloc(union bpf_attr *attr,
err = bpf_mem_alloc_init(&smap->selem_ma, smap->elem_size, false);
if (err)
goto free_smap;
err = bpf_mem_alloc_init(&smap->storage_ma, sizeof(struct bpf_local_storage), false);
if (err) {
bpf_mem_alloc_destroy(&smap->selem_ma);
goto free_smap;
}
}
smap->cache_idx = bpf_local_storage_cache_idx_get(cache);
@ -829,8 +927,10 @@ void bpf_local_storage_map_free(struct bpf_map *map,
*/
synchronize_rcu();
if (smap->bpf_ma)
if (smap->bpf_ma) {
bpf_mem_alloc_destroy(&smap->selem_ma);
bpf_mem_alloc_destroy(&smap->storage_ma);
}
kvfree(smap->buckets);
bpf_map_area_free(smap);
}