[PATCH 1/2] percpu: make @dyn_size always mean min dyn_size in first chunk init functions

[Tejun Heo <tj@kernel.org>]

In pcpu_alloc_info() and pcpu_embed_first_chunk(), @dyn_size was
ssize_t, -1 meant auto-size, 0 forced 0 and positive meant minimum
size.  There's no use case for forcing 0 and the upcoming early alloc
support always requires non-zero dynamic size.  Make @dyn_size always
mean minimum dyn_size.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
These two patches are on top of percpu#for-linus.  The branch is
available at...

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git early-alloc

It would be a good idea to add BUILD_BUG_ON() in slab to verify
allocation limits against PERCPU_DYNAMIC_EARLY_SIZE/SLOTS.  Please
note that two alloc slots might be necessary for each allocation and
there can be gaps in allocation due to alignment, so giving it some
headroom would be better.

Please let me know if it's okay for slab.  I'll push it through
percpu#for-next then.

Thanks.

 include/linux/percpu.h |    4 ++--
 mm/percpu.c            |   33 +++++++++------------------------
 2 files changed, 11 insertions(+), 26 deletions(-)

Index: work/include/linux/percpu.h
===================================================================
--- work.orig/include/linux/percpu.h
+++ work/include/linux/percpu.h
@@ -105,7 +105,7 @@ extern struct pcpu_alloc_info * __init p
 extern void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai);

 extern struct pcpu_alloc_info * __init pcpu_build_alloc_info(
-				size_t reserved_size, ssize_t dyn_size,
+				size_t reserved_size, size_t dyn_size,
 				size_t atom_size,
 				pcpu_fc_cpu_distance_fn_t cpu_distance_fn);

@@ -113,7 +113,7 @@ extern int __init pcpu_setup_first_chunk
 					 void *base_addr);

 #ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
-extern int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
+extern int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
 				size_t atom_size,
 				pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
 				pcpu_fc_alloc_fn_t alloc_fn,
Index: work/mm/percpu.c
===================================================================
--- work.orig/mm/percpu.c
+++ work/mm/percpu.c
@@ -1013,20 +1013,6 @@ phys_addr_t per_cpu_ptr_to_phys(void *ad
 		return page_to_phys(pcpu_addr_to_page(addr));
 }

-static inline size_t pcpu_calc_fc_sizes(size_t static_size,
-					size_t reserved_size,
-					ssize_t *dyn_sizep)
-{
-	size_t size_sum;
-
-	size_sum = PFN_ALIGN(static_size + reserved_size +
-			     (*dyn_sizep >= 0 ? *dyn_sizep : 0));
-	if (*dyn_sizep != 0)
-		*dyn_sizep = size_sum - static_size - reserved_size;
-
-	return size_sum;
-}
-
 /**
  * pcpu_alloc_alloc_info - allocate percpu allocation info
  * @nr_groups: the number of groups
@@ -1085,7 +1071,7 @@ void __init pcpu_free_alloc_info(struct
 /**
  * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
  * @reserved_size: the size of reserved percpu area in bytes
- * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @dyn_size: free size for dynamic allocation in bytes
  * @atom_size: allocation atom size
  * @cpu_distance_fn: callback to determine distance between cpus, optional
  *
@@ -1104,7 +1090,7 @@ void __init pcpu_free_alloc_info(struct
  * failure, ERR_PTR value is returned.
  */
 struct pcpu_alloc_info * __init pcpu_build_alloc_info(
-				size_t reserved_size, ssize_t dyn_size,
+				size_t reserved_size, size_t dyn_size,
 				size_t atom_size,
 				pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
 {
@@ -1123,13 +1109,15 @@ struct pcpu_alloc_info * __init pcpu_bui
 	memset(group_map, 0, sizeof(group_map));
 	memset(group_cnt, 0, sizeof(group_cnt));

+	size_sum = PFN_ALIGN(static_size + reserved_size + dyn_size);
+	dyn_size = size_sum - static_size - reserved_size;
+
 	/*
 	 * Determine min_unit_size, alloc_size and max_upa such that
 	 * alloc_size is multiple of atom_size and is the smallest
 	 * which can accomodate 4k aligned segments which are equal to
 	 * or larger than min_unit_size.
 	 */
-	size_sum = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_size);
 	min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);

 	alloc_size = roundup(min_unit_size, atom_size);
@@ -1532,7 +1520,7 @@ early_param("percpu_alloc", percpu_alloc
 /**
  * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
  * @reserved_size: the size of reserved percpu area in bytes
- * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @dyn_size: minimum free size for dynamic allocation in bytes
  * @atom_size: allocation atom size
  * @cpu_distance_fn: callback to determine distance between cpus, optional
  * @alloc_fn: function to allocate percpu page
@@ -1553,10 +1541,7 @@ early_param("percpu_alloc", percpu_alloc
  * vmalloc space is not orders of magnitude larger than distances
  * between node memory addresses (ie. 32bit NUMA machines).
  *
- * When @dyn_size is positive, dynamic area might be larger than
- * 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.
+ * @dyn_size specifies the minimum dynamic area size.
  *
  * If the needed size is smaller than the minimum or specified unit
  * size, the leftover is returned using @free_fn.
@@ -1564,7 +1549,7 @@ early_param("percpu_alloc", percpu_alloc
  * RETURNS:
  * 0 on success, -errno on failure.
  */
-int __init pcpu_embed_first_chunk(size_t reserved_size, ssize_t dyn_size,
+int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
 				  size_t atom_size,
 				  pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
 				  pcpu_fc_alloc_fn_t alloc_fn,
@@ -1695,7 +1680,7 @@ int __init pcpu_page_first_chunk(size_t

 	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);

-	ai = pcpu_build_alloc_info(reserved_size, -1, PAGE_SIZE, NULL);
+	ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
 	if (IS_ERR(ai))
 		return PTR_ERR(ai);
 	BUG_ON(ai->nr_groups != 1);

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