Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: don't assume existence of cpu0

mm/percpu.c

@@ -197,7 +197,12 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
 static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
 				     int page_idx)
 {
-	return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
+	/*
+	 * Any possible cpu id can be used here, so there's no need to
+	 * worry about preemption or cpu hotplug.
+	 */
+	return *pcpu_chunk_pagep(chunk, raw_smp_processor_id(),
+				 page_idx) != NULL;
 }
 
 /* set the pointer to a chunk in a page struct */
@@ -297,6 +302,14 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
 		return pcpu_first_chunk;
 	}
 
+	/*
+	 * The address is relative to unit0 which might be unused and
+	 * thus unmapped.  Offset the address to the unit space of the
+	 * current processor before looking it up in the vmalloc
+	 * space.  Note that any possible cpu id can be used here, so
+	 * there's no need to worry about preemption or cpu hotplug.
+	 */
+	addr += raw_smp_processor_id() * pcpu_unit_size;
 	return pcpu_get_page_chunk(vmalloc_to_page(addr));
 }