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Revert "bpf: Defer the free of inner map when necessary"

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This reverts commit 62fca83303 which is
commit 876673364161da50eed6b472d746ef88242b2368 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I11fc14db5e679ca1c8ff97dcd96cb2a8fd35122a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2024-02-02 22:52:03 +00:00
parent c16bb76a0c
commit 329c931b9d
3 changed files with 9 additions and 41 deletions
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7
include/linux/bpf.h
View File

@ -241,11 +241,7 @@ struct bpf_map {
*/
atomic64_t refcnt ____cacheline_aligned;
atomic64_t usercnt;
/* rcu is used before freeing and work is only used during freeing */
union {
struct work_struct work;
struct rcu_head rcu;
};
struct work_struct work;
struct mutex freeze_mutex;
atomic64_t writecnt;
/* 'Ownership' of program-containing map is claimed by the first program
@ -261,7 +257,6 @@ struct bpf_map {
} owner;
bool bypass_spec_v1;
bool frozen; /* write-once; write-protected by freeze_mutex */
bool free_after_mult_rcu_gp;
s64 __percpu *elem_count;
};

11
kernel/bpf/map_in_map.c
View File

@ -117,15 +117,10 @@ void *bpf_map_fd_get_ptr(struct bpf_map *map,
void bpf_map_fd_put_ptr(struct bpf_map *map, void *ptr, bool need_defer)
{
struct bpf_map *inner_map = ptr;
/* The inner map may still be used by both non-sleepable and sleepable
* bpf program, so free it after one RCU grace period and one tasks
* trace RCU grace period.
/* ptr->ops->map_free() has to go through one
* rcu grace period by itself.
*/
if (need_defer)
WRITE_ONCE(inner_map->free_after_mult_rcu_gp, true);
bpf_map_put(inner_map);
bpf_map_put(ptr);
}
u32 bpf_map_fd_sys_lookup_elem(void *ptr)

32
kernel/bpf/syscall.c
View File

@ -630,28 +630,6 @@ static void bpf_map_put_uref(struct bpf_map *map)
}
}
static void bpf_map_free_in_work(struct bpf_map *map)
{
INIT_WORK(&map->work, bpf_map_free_deferred);
/* Avoid spawning kworkers, since they all might contend
* for the same mutex like slab_mutex.
*/
queue_work(system_unbound_wq, &map->work);
}
static void bpf_map_free_rcu_gp(struct rcu_head *rcu)
{
bpf_map_free_in_work(container_of(rcu, struct bpf_map, rcu));
}
static void bpf_map_free_mult_rcu_gp(struct rcu_head *rcu)
{
if (rcu_trace_implies_rcu_gp())
bpf_map_free_rcu_gp(rcu);
else
call_rcu(rcu, bpf_map_free_rcu_gp);
}
/* decrement map refcnt and schedule it for freeing via workqueue
* (unrelying map implementation ops->map_free() might sleep)
*/
@ -661,11 +639,11 @@ static void __bpf_map_put(struct bpf_map *map, bool do_idr_lock)
/* bpf_map_free_id() must be called first */
bpf_map_free_id(map, do_idr_lock);
btf_put(map->btf);
if (READ_ONCE(map->free_after_mult_rcu_gp))
call_rcu_tasks_trace(&map->rcu, bpf_map_free_mult_rcu_gp);
else
bpf_map_free_in_work(map);
INIT_WORK(&map->work, bpf_map_free_deferred);
/* Avoid spawning kworkers, since they all might contend
* for the same mutex like slab_mutex.
*/
queue_work(system_unbound_wq, &map->work);
}
}