[PATCH 4/8] percpu: use negative for auto for pcpu_setup_first_chunk() arguments

Tejun Heo
2009-03-06T06:49:16Z

Impact: argument semantic cleanup

In pcpu_setup_first_chunk(), zero @unit_size and @dyn_size meant
auto-sizing. It's okay for @unit_size as 0 doesn't make sense but 0
dynamic reserve size is valid. Alos, if arch @dyn_size is calculated
from other parameters, it might end up passing in 0 @dyn_size and
malfunction when the size is automatically adjusted.

This patch makes both @unit_size and @dyn_size ssize_t and use -1 for
auto sizing.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
arch/x86/kernel/setup_percpu.c | 2 +-
include/linux/percpu.h | 5 ++-
mm/percpu.c | 46 +++++++++++++++++++++------------------
3 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index c29f301..ef3a2cd 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -344,7 +344,7 @@ static ssize_t __init setup_pcpu_4k(size_t static_size)
pr_info("PERCPU: Allocated %d 4k pages, static data %zu bytes\n",
pcpu4k_nr_static_pages, static_size);

- ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size, 0, 0, NULL,
+ ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size, -1, -1, NULL,
pcpu4k_populate_pte);
goto out_free_ar;

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index a0b4ea2..a96fc53 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -117,8 +117,9 @@ typedef struct page * (*pcpu_get_page_fn_t)(unsigned int cpu, int pageno);
typedef void (*pcpu_populate_pte_fn_t)(unsigned long addr);

extern size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
- size_t static_size, size_t unit_size,
- size_t dyn_size, void *base_addr,
+ size_t static_size,
+ ssize_t unit_size, ssize_t dyn_size,
+ void *base_addr,
pcpu_populate_pte_fn_t populate_pte_fn);

/*
diff --git a/mm/percpu.c b/mm/percpu.c
index 503ccad..a84cf99 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -824,8 +824,8 @@ EXPORT_SYMBOL_GPL(free_percpu);
* pcpu_setup_first_chunk - initialize the first percpu chunk
* @get_page_fn: callback to fetch page pointer
* @static_size: the size of static percpu area in bytes
- * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, 0 for auto
- * @dyn_size: free size for dynamic allocation in bytes, 0 for auto
+ * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
+ * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
* @base_addr: mapped address, NULL for auto
* @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
*
@@ -842,13 +842,14 @@ EXPORT_SYMBOL_GPL(free_percpu);
* indicates end of pages for the cpu. Note that @get_page_fn() must
* return the same number of pages for all cpus.
*
- * @unit_size, if non-zero, determines unit size and must be aligned
- * to PAGE_SIZE and equal to or larger than @static_size + @dyn_size.
+ * @unit_size, if non-negative, specifies unit size and must be
+ * aligned to PAGE_SIZE and equal to or larger than @static_size +
+ * @dyn_size.
*
- * @dyn_size determines the number of free bytes after the static
- * area in the first chunk. If zero, whatever left is available.
- * Specifying non-zero value make percpu leave the area after
- * @static_size + @dyn_size alone.
+ * @dyn_size, if non-negative, limits the number of bytes available
+ * for dynamic allocation in the first chunk. Specifying non-negative
+ * value make percpu leave alone the area beyond @static_size +
+ * @dyn_size.
*
* Non-null @base_addr means that the caller already allocated virtual
* region for the first chunk and mapped it. percpu must not mess
@@ -863,8 +864,9 @@ EXPORT_SYMBOL_GPL(free_percpu);
* percpu access.
*/
size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
- size_t static_size, size_t unit_size,
- size_t dyn_size, void *base_addr,
+ size_t static_size,
+ ssize_t unit_size, ssize_t dyn_size,
+ void *base_addr,
pcpu_populate_pte_fn_t populate_pte_fn)
{
static struct vm_struct first_vm;
@@ -877,13 +879,17 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
/* santiy checks */
BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC);
BUG_ON(!static_size);
- BUG_ON(!unit_size && dyn_size);
- BUG_ON(unit_size && unit_size < static_size + dyn_size);
- BUG_ON(unit_size & ~PAGE_MASK);
- BUG_ON(base_addr && !unit_size);
+ if (unit_size >= 0) {
+ BUG_ON(unit_size < static_size +
+ (dyn_size >= 0 ? dyn_size : 0));
+ BUG_ON(unit_size & ~PAGE_MASK);
+ } else {
+ BUG_ON(dyn_size >= 0);
+ BUG_ON(base_addr);
+ }
BUG_ON(base_addr && populate_pte_fn);

- if (unit_size)
+ if (unit_size >= 0)
pcpu_unit_pages = unit_size >> PAGE_SHIFT;
else
pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
@@ -894,6 +900,9 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
+ num_possible_cpus() * pcpu_unit_pages * sizeof(struct page *);

+ if (dyn_size < 0)
+ dyn_size = pcpu_unit_size - static_size;
+
/*
* Allocate chunk slots. The additional last slot is for
* empty chunks.
@@ -909,12 +918,7 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
schunk->vm = &first_vm;
schunk->map = smap;
schunk->map_alloc = ARRAY_SIZE(smap);
-
- if (dyn_size)
- schunk->free_size = dyn_size;
- else
- schunk->free_size = pcpu_unit_size - static_size;
-
+ schunk->free_size = dyn_size;
schunk->contig_hint = schunk->free_size;

schunk->map[schunk->map_used++] = -static_size;
--
1.6.0.2