[ 186/187] memblock: free allocated memblock_reserved_regions later

Greg Kroah-Hartman
2012-07-12T22:46:30Z

From: Yinghai Lu <yinghai@kernel.org>

commit 29f6738609e40227dabcc63bfb3b84b3726a75bd upstream.

memblock_free_reserved_regions() calls memblock_free(), but
memblock_free() would double reserved.regions too, so we could free the
old range for reserved.regions.

Also tj said there is another bug which could be related to this.

| I don't think we're saving any noticeable
| amount by doing this "free - give it to page allocator - reserve
| again" dancing. We should just allocate regions aligned to page
| boundaries and free them later when memblock is no longer in use.

in that case, when DEBUG_PAGEALLOC, will get panic:

memblock_free: [0x0000102febc080-0x0000102febf080] memblock_free_reserved_regions+0x37/0x39
BUG: unable to handle kernel paging request at ffff88102febd948
IP: [<ffffffff836a5774>] __next_free_mem_range+0x9b/0x155
PGD 4826063 PUD cf67a067 PMD cf7fa067 PTE 800000102febd160
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
CPU 0
Pid: 0, comm: swapper Not tainted 3.5.0-rc2-next-20120614-sasha #447
RIP: 0010:[<ffffffff836a5774>] [<ffffffff836a5774>] __next_free_mem_range+0x9b/0x155

See the discussion at https://lkml.org/lkml/2012/6/13/469

So try to allocate with PAGE_SIZE alignment and free it later.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/memblock.h | 4 ---
mm/memblock.c | 51 +++++++++++++++++++++--------------------------
mm/nobootmem.c | 36 ++++++++++++++++++++-------------
3 files changed, 46 insertions(+), 45 deletions(-)

--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -50,9 +50,7 @@ phys_addr_t memblock_find_in_range_node(
phys_addr_t size, phys_addr_t align, int nid);
phys_addr_t memblock_find_in_range(phys_addr_t start, phys_addr_t end,
phys_addr_t size, phys_addr_t align);
-int memblock_free_reserved_regions(void);
-int memblock_reserve_reserved_regions(void);
-
+phys_addr_t get_allocated_memblock_reserved_regions_info(phys_addr_t *addr);
void memblock_allow_resize(void);
int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid);
int memblock_add(phys_addr_t base, phys_addr_t size);
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -143,30 +143,6 @@ phys_addr_t __init_memblock memblock_fin
MAX_NUMNODES);
}

-/*
- * Free memblock.reserved.regions
- */
-int __init_memblock memblock_free_reserved_regions(void)
-{
- if (memblock.reserved.regions == memblock_reserved_init_regions)
- return 0;
-
- return memblock_free(__pa(memblock.reserved.regions),
- sizeof(struct memblock_region) * memblock.reserved.max);
-}
-
-/*
- * Reserve memblock.reserved.regions
- */
-int __init_memblock memblock_reserve_reserved_regions(void)
-{
- if (memblock.reserved.regions == memblock_reserved_init_regions)
- return 0;
-
- return memblock_reserve(__pa(memblock.reserved.regions),
- sizeof(struct memblock_region) * memblock.reserved.max);
-}
-
static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
{
type->total_size -= type->regions[r].size;
@@ -184,6 +160,18 @@ static void __init_memblock memblock_rem
}
}

+phys_addr_t __init_memblock get_allocated_memblock_reserved_regions_info(
+ phys_addr_t *addr)
+{
+ if (memblock.reserved.regions == memblock_reserved_init_regions)
+ return 0;
+
+ *addr = __pa(memblock.reserved.regions);
+
+ return PAGE_ALIGN(sizeof(struct memblock_region) *
+ memblock.reserved.max);
+}
+
/**
* memblock_double_array - double the size of the memblock regions array
* @type: memblock type of the regions array being doubled
@@ -204,6 +192,7 @@ static int __init_memblock memblock_doub
phys_addr_t new_area_size)
{
struct memblock_region *new_array, *old_array;
+ phys_addr_t old_alloc_size, new_alloc_size;
phys_addr_t old_size, new_size, addr;
int use_slab = slab_is_available();
int *in_slab;
@@ -217,6 +206,12 @@ static int __init_memblock memblock_doub
/* Calculate new doubled size */
old_size = type->max * sizeof(struct memblock_region);
new_size = old_size << 1;
+ /*
+ * We need to allocated new one align to PAGE_SIZE,
+ * so we can free them completely later.
+ */
+ old_alloc_size = PAGE_ALIGN(old_size);
+ new_alloc_size = PAGE_ALIGN(new_size);

/* Retrieve the slab flag */
if (type == &memblock.memory)
@@ -245,11 +240,11 @@ static int __init_memblock memblock_doub

addr = memblock_find_in_range(new_area_start + new_area_size,
memblock.current_limit,
- new_size, sizeof(phys_addr_t));
+ new_alloc_size, PAGE_SIZE);
if (!addr && new_area_size)
addr = memblock_find_in_range(0,
min(new_area_start, memblock.current_limit),
- new_size, sizeof(phys_addr_t));
+ new_alloc_size, PAGE_SIZE);

new_array = addr ? __va(addr) : 0;
}
@@ -279,13 +274,13 @@ static int __init_memblock memblock_doub
kfree(old_array);
else if (old_array != memblock_memory_init_regions &&
old_array != memblock_reserved_init_regions)
- memblock_free(__pa(old_array), old_size);
+ memblock_free(__pa(old_array), old_alloc_size);

/* Reserve the new array if that comes from the memblock.
* Otherwise, we needn't do it
*/
if (!use_slab)
- BUG_ON(memblock_reserve(addr, new_size));
+ BUG_ON(memblock_reserve(addr, new_alloc_size));

/* Update slab flag */
*in_slab = use_slab;
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -105,27 +105,35 @@ static void __init __free_pages_memory(u
__free_pages_bootmem(pfn_to_page(i), 0);
}

+static unsigned long __init __free_memory_core(phys_addr_t start,
+ phys_addr_t end)
+{
+ unsigned long start_pfn = PFN_UP(start);
+ unsigned long end_pfn = min_t(unsigned long,
+ PFN_DOWN(end), max_low_pfn);
+
+ if (start_pfn > end_pfn)
+ return 0;
+
+ __free_pages_memory(start_pfn, end_pfn);
+
+ return end_pfn - start_pfn;
+}
+
unsigned long __init free_low_memory_core_early(int nodeid)
{
unsigned long count = 0;
- phys_addr_t start, end;
+ phys_addr_t start, end, size;
u64 i;

- /* free reserved array temporarily so that it's treated as free area */
- memblock_free_reserved_regions();
+ for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL)
+ count += __free_memory_core(start, end);

- for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL) {
- unsigned long start_pfn = PFN_UP(start);
- unsigned long end_pfn = min_t(unsigned long,
- PFN_DOWN(end), max_low_pfn);
- if (start_pfn < end_pfn) {
- __free_pages_memory(start_pfn, end_pfn);
- count += end_pfn - start_pfn;
- }
- }
+ /* free range that is used for reserved array if we allocate it */
+ size = get_allocated_memblock_reserved_regions_info(&start);
+ if (size)
+ count += __free_memory_core(start, start + size);

- /* put region array back? */
- memblock_reserve_reserved_regions();
return count;
}