Patch "memblock: free allocated memblock_reserved_regions later" has been added to the 3.4-stable tree

This is a note to let you know that I've just added the patch titled

memblock: free allocated memblock_reserved_regions later

to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
memblock-free-allocated-memblock_reserved_regions-later.patch
and it can be found in the queue-3.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yinghai Lu <[email protected]>
Date: Wed, 11 Jul 2012 14:02:56 -0700
Subject: memblock: free allocated memblock_reserved_regions later

From: Yinghai Lu <[email protected]>

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.

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

@@ -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);

@@ -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;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.4/memblock-free-allocated-memblock_reserved_regions-later.patch queue-3.4/mm-memblock-fix-overlapping-allocation-when-doubling-reserved-array.patch