[PATCH 6/6] percpu: simplify pcpu_setup_first_chunk()

Tejun Heo
2009-06-17T04:08:25Z

Now that all first chunk allocator helpers allocate and map the first
chunk themselves, there's no need to have optional default alloc/map
in pcpu_setup_first_chunk(). Drop @populate_pte_fn and only leave
@dyn_size optional and make all other params mandatory.

This makes it much easier to follow what pcpu_setup_first_chunk() is
doing and what actual differences tweaking each parameter results in.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
include/linux/percpu.h | 5 +-
mm/percpu.c | 104 ++++++++++++++----------------------------------
2 files changed, 32 insertions(+), 77 deletions(-)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 9f6bfd7..ec64357 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -66,9 +66,8 @@ typedef void (*pcpu_fc_map_fn_t)(void *ptr, size_t size, void *addr);

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

extern ssize_t __init pcpu_embed_first_chunk(
size_t static_size, size_t reserved_size,
diff --git a/mm/percpu.c b/mm/percpu.c
index 17dfb7c..452d3f3 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -983,24 +983,22 @@ 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
- * @reserved_size: the size of reserved percpu area in bytes
+ * @reserved_size: the size of reserved percpu area in bytes, 0 for none
* @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
- * @base_addr: mapped address, NULL for auto
- * @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
+ * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE
+ * @base_addr: mapped address
*
* Initialize the first percpu chunk which contains the kernel static
* perpcu area. This function is to be called from arch percpu area
- * setup path. The first two parameters are mandatory. The rest are
- * optional.
+ * setup path.
*
* @get_page_fn() should return pointer to percpu page given cpu
* number and page number. It should at least return enough pages to
* cover the static area. The returned pages for static area should
- * have been initialized with valid data. If @unit_size is specified,
- * it can also return pages after the static area. NULL return
- * indicates end of pages for the cpu. Note that @get_page_fn() must
- * return the same number of pages for all cpus.
+ * have been initialized with valid data. It can also return pages
+ * after the static area. NULL return indicates end of pages for the
+ * cpu. Note that @get_page_fn() must return the same number of pages
+ * for all cpus.
*
* @reserved_size, if non-zero, specifies the amount of bytes to
* reserve after the static area in the first chunk. This reserves
@@ -1015,17 +1013,12 @@ EXPORT_SYMBOL_GPL(free_percpu);
* non-negative value makes percpu leave alone the area beyond
* @static_size + @reserved_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 +
- * @reserved_size + if non-negative, @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
- * with the chunk. Note that @base_addr with 0 @unit_size or non-NULL
- * @populate_pte_fn doesn't make any sense.
+ * @unit_size specifies unit size and must be aligned to PAGE_SIZE and
+ * equal to or larger than @static_size + @reserved_size + if
+ * non-negative, @dyn_size.
*
- * @populate_pte_fn is used to populate the pagetable. NULL means the
- * caller already populated the pagetable.
+ * The caller should have mapped the first chunk at @base_addr and
+ * copied static data to each unit.
*
* If the first chunk ends up with both reserved and dynamic areas, it
* is served by two chunks - one to serve the core static and reserved
@@ -1040,9 +1033,8 @@ EXPORT_SYMBOL_GPL(free_percpu);
*/
size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
size_t static_size, size_t reserved_size,
- ssize_t dyn_size, ssize_t unit_size,
- void *base_addr,
- pcpu_fc_populate_pte_fn_t populate_pte_fn)
+ ssize_t dyn_size, size_t unit_size,
+ void *base_addr)
{
static struct vm_struct first_vm;
static int smap[2], dmap[2];
@@ -1050,27 +1042,18 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
(dyn_size >= 0 ? dyn_size : 0);
struct pcpu_chunk *schunk, *dchunk = NULL;
unsigned int cpu;
- int nr_pages;
- int err, i;
+ int i, nr_pages;

/* santiy checks */
BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
BUG_ON(!static_size);
- if (unit_size >= 0) {
- BUG_ON(unit_size < size_sum);
- BUG_ON(unit_size & ~PAGE_MASK);
- BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);
- } else
- BUG_ON(base_addr);
- BUG_ON(base_addr && populate_pte_fn);
-
- if (unit_size >= 0)
- pcpu_unit_pages = unit_size >> PAGE_SHIFT;
- else
- pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
- PFN_UP(size_sum));
+ BUG_ON(!base_addr);
+ BUG_ON(unit_size < size_sum);
+ BUG_ON(unit_size & ~PAGE_MASK);
+ BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);

+ pcpu_unit_pages = unit_size >> PAGE_SHIFT;
pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
@@ -1079,6 +1062,10 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
if (dyn_size < 0)
dyn_size = pcpu_unit_size - static_size - reserved_size;

+ first_vm.flags = VM_ALLOC;
+ first_vm.size = pcpu_chunk_size;
+ first_vm.addr = base_addr;
+
/*
* Allocate chunk slots. The additional last slot is for
* empty chunks.
@@ -1101,6 +1088,7 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
schunk->map = smap;
schunk->map_alloc = ARRAY_SIZE(smap);
schunk->page = schunk->page_ar;
+ schunk->immutable = true;

if (reserved_size) {
schunk->free_size = reserved_size;
@@ -1124,31 +1112,13 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
dchunk->map = dmap;
dchunk->map_alloc = ARRAY_SIZE(dmap);
dchunk->page = schunk->page_ar; /* share page map with schunk */
+ dchunk->immutable = true;

dchunk->contig_hint = dchunk->free_size = dyn_size;
dchunk->map[dchunk->map_used++] = -pcpu_reserved_chunk_limit;
dchunk->map[dchunk->map_used++] = dchunk->free_size;
}

- /* allocate vm address */
- first_vm.flags = VM_ALLOC;
- first_vm.size = pcpu_chunk_size;
-
- if (!base_addr)
- vm_area_register_early(&first_vm, PAGE_SIZE);
- else {
- /*
- * Pages already mapped. No need to remap into
- * vmalloc area. In this case the first chunks can't
- * be mapped or unmapped by percpu and are marked
- * immutable.
- */
- first_vm.addr = base_addr;
- schunk->immutable = true;
- if (dchunk)
- dchunk->immutable = true;
- }
-
/* assign pages */
nr_pages = -1;
for_each_possible_cpu(cpu) {
@@ -1168,19 +1138,6 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
BUG_ON(nr_pages != i);
}

- /* map them */
- if (populate_pte_fn) {
- for_each_possible_cpu(cpu)
- for (i = 0; i < nr_pages; i++)
- populate_pte_fn(pcpu_chunk_addr(schunk,
- cpu, i));
-
- err = pcpu_map(schunk, 0, nr_pages);
- if (err)
- panic("failed to setup static percpu area, err=%d\n",
- err);
- }
-
/* link the first chunk in */
pcpu_first_chunk = dchunk ?: schunk;
pcpu_chunk_relocate(pcpu_first_chunk, -1);
@@ -1282,7 +1239,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,

return pcpu_setup_first_chunk(pcpue_get_page, static_size,
reserved_size, dyn_size,
- pcpue_unit_size, pcpue_ptr, NULL);
+ pcpue_unit_size, pcpue_ptr);
}

/*
@@ -1387,8 +1344,7 @@ ssize_t __init pcpu_4k_first_chunk(size_t static_size, size_t reserved_size,

ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size,
reserved_size, -1,
- pcpu4k_unit_pages << PAGE_SHIFT, vm.addr,
- NULL);
+ pcpu4k_unit_pages << PAGE_SHIFT, vm.addr);
goto out_free_ar;

enomem:
@@ -1521,7 +1477,7 @@ ssize_t __init pcpu_lpage_first_chunk(size_t static_size, size_t reserved_size,

ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
reserved_size, dyn_size, pcpul_unit_size,
- pcpul_vm.addr, NULL);
+ pcpul_vm.addr);

/* sort pcpul_map array for pcpu_lpage_remapped() */
for (i = 0; i < num_possible_cpus() - 1; i++)
--
1.6.0.2