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bpf: Fix usage of trace RCU in local storage. 

bpf_{sk,task,inode}_storage_free() do not need to use
call_rcu_tasks_trace as no BPF program should be accessing the owner
as it's being destroyed. The only other reader at this point is
bpf_local_storage_map_free() which uses normal RCU.

The only path that needs trace RCU are:

* bpf_local_storage_{delete,update} helpers
* map_{delete,update}_elem() syscalls

Fixes: 0fe4b381a5 ("bpf: Allow bpf_local_storage to be used by sleepable programs")
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220418155158.2865678-1-kpsingh@kernel.org
This commit is contained in:
KP Singh 2022-04-18 15:51:58 +00:00 committed by Alexei Starovoitov
parent 0e5aefa334
commit dcf456c9a0
5 changed files with 28 additions and 19 deletions
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4
include/linux/bpf_local_storage.h
View File

@ -143,9 +143,9 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
struct bpf_local_storage_elem *selem,
bool uncharge_omem);
bool uncharge_omem, bool use_trace_rcu);
void bpf_selem_unlink(struct bpf_local_storage_elem *selem);
void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu);
void bpf_selem_link_map(struct bpf_local_storage_map *smap,
struct bpf_local_storage_elem *selem);

4
kernel/bpf/bpf_inode_storage.c
View File

@ -90,7 +90,7 @@ void bpf_inode_storage_free(struct inode *inode)
*/
bpf_selem_unlink_map(selem);
free_inode_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, false);
local_storage, selem, false, false);
}
raw_spin_unlock_bh(&local_storage->lock);
rcu_read_unlock();
@ -149,7 +149,7 @@ static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata));
bpf_selem_unlink(SELEM(sdata), true);
return 0;
}

29
kernel/bpf/bpf_local_storage.c
View File

@ -106,7 +106,7 @@ static void bpf_selem_free_rcu(struct rcu_head *rcu)
*/
bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
struct bpf_local_storage_elem *selem,
bool uncharge_mem)
bool uncharge_mem, bool use_trace_rcu)
{
struct bpf_local_storage_map *smap;
bool free_local_storage;
@ -150,11 +150,16 @@ bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
SDATA(selem))
RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
if (use_trace_rcu)
call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
else
kfree_rcu(selem, rcu);
return free_local_storage;
}
static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
bool use_trace_rcu)
{
struct bpf_local_storage *local_storage;
bool free_local_storage = false;
@ -169,12 +174,16 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
raw_spin_lock_irqsave(&local_storage->lock, flags);
if (likely(selem_linked_to_storage(selem)))
free_local_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, true);
local_storage, selem, true, use_trace_rcu);
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
if (free_local_storage)
call_rcu_tasks_trace(&local_storage->rcu,
if (free_local_storage) {
if (use_trace_rcu)
call_rcu_tasks_trace(&local_storage->rcu,
bpf_local_storage_free_rcu);
else
kfree_rcu(local_storage, rcu);
}
}
void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
@ -214,14 +223,14 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap,
raw_spin_unlock_irqrestore(&b->lock, flags);
}
void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu)
{
/* Always unlink from map before unlinking from local_storage
* because selem will be freed after successfully unlinked from
* the local_storage.
*/
bpf_selem_unlink_map(selem);
__bpf_selem_unlink_storage(selem);
__bpf_selem_unlink_storage(selem, use_trace_rcu);
}
struct bpf_local_storage_data *
@ -466,7 +475,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
if (old_sdata) {
bpf_selem_unlink_map(SELEM(old_sdata));
bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
false);
false, true);
}
unlock:
@ -548,7 +557,7 @@ void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
migrate_disable();
__this_cpu_inc(*busy_counter);
}
bpf_selem_unlink(selem);
bpf_selem_unlink(selem, false);
if (busy_counter) {
__this_cpu_dec(*busy_counter);
migrate_enable();

4
kernel/bpf/bpf_task_storage.c
View File

@ -102,7 +102,7 @@ void bpf_task_storage_free(struct task_struct *task)
*/
bpf_selem_unlink_map(selem);
free_task_storage = bpf_selem_unlink_storage_nolock(
local_storage, selem, false);
local_storage, selem, false, false);
}
raw_spin_unlock_irqrestore(&local_storage->lock, flags);
bpf_task_storage_unlock();
@ -192,7 +192,7 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata));
bpf_selem_unlink(SELEM(sdata), true);
return 0;
}

6
net/core/bpf_sk_storage.c
View File

@ -40,7 +40,7 @@ static int bpf_sk_storage_del(struct sock *sk, struct bpf_map *map)
if (!sdata)
return -ENOENT;
bpf_selem_unlink(SELEM(sdata));
bpf_selem_unlink(SELEM(sdata), true);
return 0;
}
@ -75,8 +75,8 @@ void bpf_sk_storage_free(struct sock *sk)
* sk_storage.
*/
bpf_selem_unlink_map(selem);
free_sk_storage = bpf_selem_unlink_storage_nolock(sk_storage,
selem, true);
free_sk_storage = bpf_selem_unlink_storage_nolock(
sk_storage, selem, true, false);
}
raw_spin_unlock_bh(&sk_storage->lock);
rcu_read_unlock();