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-rw-r--r--mm/percpu.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index 2473ff06dc76..3bb810a72006 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -978,6 +978,17 @@ bool is_kernel_percpu_address(unsigned long addr)
* address. The caller is responsible for ensuring @addr stays valid
* until this function finishes.
*
+ * percpu allocator has special setup for the first chunk, which currently
+ * supports either embedding in linear address space or vmalloc mapping,
+ * and, from the second one, the backing allocator (currently either vm or
+ * km) provides translation.
+ *
+ * The addr can be tranlated simply without checking if it falls into the
+ * first chunk. But the current code reflects better how percpu allocator
+ * actually works, and the verification can discover both bugs in percpu
+ * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
+ * code.
+ *
* RETURNS:
* The physical address for @addr.
*/