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mm/percpu.c: introduce pcpu_alloc_size()

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Introduce pcpu_alloc_size() to get the size of the dynamic per-cpu
area. It will be used by bpf memory allocator in the following patches.
BPF memory allocator maintains per-cpu area caches for multiple area
sizes and its free API only has the to-be-freed per-cpu pointer, so it
needs the size of dynamic per-cpu area to select the corresponding cache
when bpf program frees the dynamic per-cpu pointer.

Acked-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231020133202.4043247-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Hou Tao 2023-10-20 21:31:57 +08:00 committed by Alexei Starovoitov
parent 394e6869f0
commit b460bc8302
2 changed files with 32 additions and 0 deletions
include/linux
percpu.h
mm
percpu.c

1
include/linux/percpu.h

@ -132,6 +132,7 @@ extern void __init setup_per_cpu_areas(void);
extern void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp) __alloc_size(1);
extern void __percpu *__alloc_percpu(size_t size, size_t align) __alloc_size(1);
extern void free_percpu(void __percpu *__pdata);
extern size_t pcpu_alloc_size(void __percpu *__pdata);
DEFINE_FREE(free_percpu, void __percpu *, free_percpu(_T))

31
mm/percpu.c

@ -2244,6 +2244,37 @@ static void pcpu_balance_workfn(struct work_struct *work)
mutex_unlock(&pcpu_alloc_mutex);
}
/**
* pcpu_alloc_size - the size of the dynamic percpu area
* @ptr: pointer to the dynamic percpu area
*
* Returns the size of the @ptr allocation. This is undefined for statically
* defined percpu variables as there is no corresponding chunk->bound_map.
*
* RETURNS:
* The size of the dynamic percpu area.
*
* CONTEXT:
* Can be called from atomic context.
*/
size_t pcpu_alloc_size(void __percpu *ptr)
{
struct pcpu_chunk *chunk;
unsigned long bit_off, end;
void *addr;
if (!ptr)
return 0;
addr = __pcpu_ptr_to_addr(ptr);
/* No pcpu_lock here: ptr has not been freed, so chunk is still alive */
chunk = pcpu_chunk_addr_search(addr);
bit_off = (addr - chunk->base_addr) / PCPU_MIN_ALLOC_SIZE;
end = find_next_bit(chunk->bound_map, pcpu_chunk_map_bits(chunk),
bit_off + 1);
return (end - bit_off) * PCPU_MIN_ALLOC_SIZE;
}
/**
* free_percpu - free percpu area
* @ptr: pointer to area to free