percpu: drop @unit_size from embed first chunk allocator

The only extra feature @unit_size provides is making dead space at the
end of the first chunk which doesn't have any valid usecase.  Drop the
parameter.  This will increase consistency with generalized 4k
allocator.

James Bottomley spotted missing conversion for the default
setup_per_cpu_areas() which caused build breakage on all arcsh which
use it.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/setup_percpu.c

@@ -342,7 +342,7 @@ static ssize_t __init setup_pcpu_embed(size_t static_size, bool chosen)
 		return -EINVAL;
 
 	return pcpu_embed_first_chunk(static_size, PERCPU_FIRST_CHUNK_RESERVE,
-				      reserve - PERCPU_FIRST_CHUNK_RESERVE, -1);
+				      reserve - PERCPU_FIRST_CHUNK_RESERVE);
 }
 
 /*

include/linux/percpu.h

@@ -69,7 +69,7 @@ extern size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
 
 extern ssize_t __init pcpu_embed_first_chunk(
 				size_t static_size, size_t reserved_size,
-				ssize_t dyn_size, ssize_t unit_size);
+				ssize_t dyn_size);
 
 /*
  * Use this to get to a cpu's version of the per-cpu object

mm/percpu.c

@@ -1207,7 +1207,6 @@ static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
  * @static_size: the size of static percpu area in bytes
  * @reserved_size: the size of reserved percpu area in bytes
  * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
- * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
  *
  * This is a helper to ease setting up embedded first percpu chunk and
  * can be called where pcpu_setup_first_chunk() is expected.
@@ -1219,9 +1218,9 @@ static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
  * page size.
  *
  * When @dyn_size is positive, dynamic area might be larger than
- * specified to fill page alignment.  Also, when @dyn_size is auto,
- * @dyn_size does not fill the whole first chunk but only what's
- * necessary for page alignment after static and reserved areas.
+ * specified to fill page alignment.  When @dyn_size is auto,
+ * @dyn_size is just big enough to fill page alignment after static
+ * and reserved areas.
  *
  * If the needed size is smaller than the minimum or specified unit
  * size, the leftover is returned to the bootmem allocator.
@@ -1231,7 +1230,7 @@ static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
  * percpu access on success, -errno on failure.
  */
 ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
-				      ssize_t dyn_size, ssize_t unit_size)
+				      ssize_t dyn_size)
 {
 	size_t chunk_size;
 	unsigned int cpu;
@@ -1242,12 +1241,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 	if (dyn_size != 0)
 		dyn_size = pcpue_size - static_size - reserved_size;
 
-	if (unit_size >= 0) {
-		BUG_ON(unit_size < pcpue_size);
-		pcpue_unit_size = unit_size;
-	} else
-		pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
-
+	pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
 	chunk_size = pcpue_unit_size * num_possible_cpus();
 
 	pcpue_ptr = __alloc_bootmem_nopanic(chunk_size, PAGE_SIZE,
@@ -1304,7 +1298,7 @@ void __init setup_per_cpu_areas(void)
 	 * what the legacy allocator did.
 	 */
 	unit_size = pcpu_embed_first_chunk(static_size, PERCPU_MODULE_RESERVE,
-					   PERCPU_DYNAMIC_RESERVE, -1);
+					   PERCPU_DYNAMIC_RESERVE);
 	if (unit_size < 0)
 		panic("Failed to initialized percpu areas.");