percpu: remove pcpu_alloc_size()

pcpu_alloc_size() was added in 7ac5c53e "mm/percpu.c: introduce
pcpu_alloc_size()", which is used to get the allocated memory size in bpf.
However, pcpu_alloc_size() is no longer used in "bpf: Use c->unit_size to
select target cache during free" because its actuall allocated memory size
may change at runtime due to its slab merging mechanism.  Therefore,
pcpu_alloc_size() can be removed.

Link: https://lkml.kernel.org/r/tencent_AD5C50E8D78C07A3CE539BD5F6BF39706507@qq.comSigned-off-by: Jianhui Zhou <912460177@qq.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: JonasZhou <JonasZhou@zhaoxin.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/percpu.h

@@ -135,7 +135,6 @@ extern void __init setup_per_cpu_areas(void);
 
 extern void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved,
 				   gfp_t gfp) __alloc_size(1);
-extern size_t pcpu_alloc_size(void __percpu *__pdata);
 
 #define __alloc_percpu_gfp(_size, _align, _gfp)				\
 	alloc_hooks(pcpu_alloc_noprof(_size, _align, false, _gfp))

mm/percpu.c

@@ -2216,37 +2216,6 @@ 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