Commit b460bc83 authored by Hou Tao's avatar Hou Tao Committed by Alexei Starovoitov
Browse files

mm/percpu.c: introduce pcpu_alloc_size() 



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: default avatarDennis Zhou <dennis@kernel.org>
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231020133202.4043247-3-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 394e6869

include/linux/percpu.h

+1 −0
Original line number Diff line number Diff line
@@ -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))

mm/percpu.c

+31 −0
Original line number Diff line number Diff line
@@ -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