[PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Mel Gorman]

There are problems in the use of SPARSEMEM and pageblock flags that causes
problems on ia64.

The first part of the problem is that units are incorrect in
SECTION_BLOCKFLAGS_BITS computation. This results in a map_section's
section_mem_map being treated as part of a bitmap which isn't good. This
was evident with an invalid virtual address when mem_init attempted to free
bootmem pages while relinquishing control from the bootmem allocator.

The second part of the problem occurs because the pageblock flags bitmap is
be located with the mem_section. The SECTIONS_PER_ROOT computation using
sizeof (mem_section) may not be a power of 2 depending on the size of the
bitmap. This renders masks and other such things not power of 2 base. This
issue was seen with SPARSEMEM_EXTREME on ia64. This patch moves the bitmap
outside of mem_section and uses a pointer instead in the mem_section. The
bitmaps are allocated when the section is being initialised.

Note that sparse_early_usemap_alloc() does not use alloc_remap() like
sparse_early_mem_map_alloc(). The allocation required for the bitmap on x86,
the only architecture that uses alloc_remap is typically smaller than a cache
line. alloc_remap() pads out allocations to the cache size which would be
a needless waste.

Credit to Bob Picco for identifying the original problem and effecting a
fix for the SECTION_BLOCKFLAGS_BITS calculation. Credit to Andy Whitcroft
for devising the best way of allocating the bitmaps only when required for
the section.

Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>

 include/linux/mmzone.h |    6 ++++--
 mm/sparse.c            |   49 ++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 50 insertions(+), 5 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.21-rc2-mm2-clean/include/linux/mmzone.h linux-2.6.21-rc2-mm2-sparsemem_rootsize_fix/include/linux/mmzone.h
--- linux-2.6.21-rc2-mm2-clean/include/linux/mmzone.h	2007-03-09 10:22:08.000000000 +0000
+++ linux-2.6.21-rc2-mm2-sparsemem_rootsize_fix/include/linux/mmzone.h	2007-03-09 19:42:00.000000000 +0000
@@ -705,7 +705,7 @@ extern struct zone *next_zone(struct zon
 #define PAGE_SECTION_MASK	(~(PAGES_PER_SECTION-1))
 
 #define SECTION_BLOCKFLAGS_BITS \
-		((SECTION_SIZE_BITS - (MAX_ORDER-1)) * NR_PAGEBLOCK_BITS)
+		((1 << (PFN_SECTION_SHIFT - (MAX_ORDER-1))) * NR_PAGEBLOCK_BITS)
 
 #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
 #error Allocator MAX_ORDER exceeds SECTION_SIZE
@@ -726,7 +726,9 @@ struct mem_section {
 	 * before using it wrong.
 	 */
 	unsigned long section_mem_map;
-	DECLARE_BITMAP(pageblock_flags, SECTION_BLOCKFLAGS_BITS);
+
+	/* See declaration of similar field in struct zone */
+	unsigned long *pageblock_flags;
 };
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.21-rc2-mm2-clean/mm/sparse.c linux-2.6.21-rc2-mm2-sparsemem_rootsize_fix/mm/sparse.c
--- linux-2.6.21-rc2-mm2-clean/mm/sparse.c	2007-02-28 04:59:12.000000000 +0000
+++ linux-2.6.21-rc2-mm2-sparsemem_rootsize_fix/mm/sparse.c	2007-03-09 19:45:15.000000000 +0000
@@ -198,13 +198,15 @@ struct page *sparse_decode_mem_map(unsig
 }
 
 static int sparse_init_one_section(struct mem_section *ms,
-		unsigned long pnum, struct page *mem_map)
+		unsigned long pnum, struct page *mem_map,
+		unsigned long *pageblock_bitmap)
 {
 	if (!valid_section(ms))
 		return -EINVAL;
 
 	ms->section_mem_map &= ~SECTION_MAP_MASK;
 	ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum);
+	ms->pageblock_flags = pageblock_bitmap;
 
 	return 1;
 }
@@ -268,6 +270,33 @@ static void __kfree_section_memmap(struc
 			   get_order(sizeof(struct page) * nr_pages));
 }
 
+static unsigned long usemap_size(void)
+{
+	unsigned long size_bytes;
+ 	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
+	size_bytes = roundup(size_bytes, sizeof(unsigned long));
+	return size_bytes;
+}
+
+static unsigned long *__kmalloc_section_usemap(void)
+{
+	return kmalloc(usemap_size(), GFP_KERNEL);
+}
+
+static unsigned long *sparse_early_usemap_alloc(unsigned long pnum)
+{
+	unsigned long *usemap;
+	struct mem_section *ms = __nr_to_section(pnum);
+	int nid = sparse_early_nid(ms);
+
+	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
+	if (usemap)
+		return usemap;
+
+	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
+	return NULL;
+}
+
 /*
  * Allocate the accumulated non-linear sections, allocate a mem_map
  * for each and record the physical to section mapping.
@@ -276,6 +305,7 @@ void sparse_init(void)
 {
 	unsigned long pnum;
 	struct page *map;
+	unsigned long *usemap;
 
 	for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
 		if (!valid_section_nr(pnum))
@@ -284,7 +314,13 @@ void sparse_init(void)
 		map = sparse_early_mem_map_alloc(pnum);
 		if (!map)
 			continue;
-		sparse_init_one_section(__nr_to_section(pnum), pnum, map);
+
+		usemap = sparse_early_usemap_alloc(pnum);
+		if (!usemap)
+			continue;
+
+		sparse_init_one_section(__nr_to_section(pnum), pnum, map,
+								usemap);
 	}
 }
 
@@ -300,6 +336,7 @@ int sparse_add_one_section(struct zone *
 	struct pglist_data *pgdat = zone->zone_pgdat;
 	struct mem_section *ms;
 	struct page *memmap;
+	unsigned long *usemap;
 	unsigned long flags;
 	int ret;
 
@@ -309,6 +346,7 @@ int sparse_add_one_section(struct zone *
 	 */
 	sparse_index_init(section_nr, pgdat->node_id);
 	memmap = __kmalloc_section_memmap(nr_pages);
+	usemap = __kmalloc_section_usemap();
 
 	pgdat_resize_lock(pgdat, &flags);
 
@@ -317,9 +355,14 @@ int sparse_add_one_section(struct zone *
 		ret = -EEXIST;
 		goto out;
 	}
+
+	if (!usemap) {
+		ret = -ENOMEM;
+		goto out;
+	}
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 
-	ret = sparse_init_one_section(ms, section_nr, memmap);
+	ret = sparse_init_one_section(ms, section_nr, memmap, usemap);
 
 out:
 	pgdat_resize_unlock(pgdat, &flags);

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Andrew Morton]

On Tue, 13 Mar 2007 10:42:02 +0000 mel@skynet.ie (Mel Gorman) wrote:

> There are problems in the use of SPARSEMEM and pageblock flags that causes
> problems on ia64.
> 
> The first part of the problem is that units are incorrect in
> SECTION_BLOCKFLAGS_BITS computation. This results in a map_section's
> section_mem_map being treated as part of a bitmap which isn't good. This
> was evident with an invalid virtual address when mem_init attempted to free
> bootmem pages while relinquishing control from the bootmem allocator.
> 
> The second part of the problem occurs because the pageblock flags bitmap is
> be located with the mem_section. The SECTIONS_PER_ROOT computation using
> sizeof (mem_section) may not be a power of 2 depending on the size of the
> bitmap. This renders masks and other such things not power of 2 base. This
> issue was seen with SPARSEMEM_EXTREME on ia64. This patch moves the bitmap
> outside of mem_section and uses a pointer instead in the mem_section. The
> bitmaps are allocated when the section is being initialised.
> 
> Note that sparse_early_usemap_alloc() does not use alloc_remap() like
> sparse_early_mem_map_alloc(). The allocation required for the bitmap on x86,
> the only architecture that uses alloc_remap is typically smaller than a cache
> line. alloc_remap() pads out allocations to the cache size which would be
> a needless waste.
> 
> Credit to Bob Picco for identifying the original problem and effecting a
> fix for the SECTION_BLOCKFLAGS_BITS calculation. Credit to Andy Whitcroft
> for devising the best way of allocating the bitmaps only when required for
> the section.

SuperH allmodconfig blew up:

mm/sparse.c: In function `sparse_init':
mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
mm/sparse.c: In function `sparse_add_one_section':
mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
mm/sparse.c:553: warning: assignment makes pointer from integer without a cast

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Mel Gorman]

On (24/07/07 22:01), Andrew Morton didst pronounce:
> On Tue, 13 Mar 2007 10:42:02 +0000 mel@skynet.ie (Mel Gorman) wrote:
> 
> > There are problems in the use of SPARSEMEM and pageblock flags that causes
> > problems on ia64.
> > 
> > The first part of the problem is that units are incorrect in
> > SECTION_BLOCKFLAGS_BITS computation. This results in a map_section's
> > section_mem_map being treated as part of a bitmap which isn't good. This
> > was evident with an invalid virtual address when mem_init attempted to free
> > bootmem pages while relinquishing control from the bootmem allocator.
> > 
> > The second part of the problem occurs because the pageblock flags bitmap is
> > be located with the mem_section. The SECTIONS_PER_ROOT computation using
> > sizeof (mem_section) may not be a power of 2 depending on the size of the
> > bitmap. This renders masks and other such things not power of 2 base. This
> > issue was seen with SPARSEMEM_EXTREME on ia64. This patch moves the bitmap
> > outside of mem_section and uses a pointer instead in the mem_section. The
> > bitmaps are allocated when the section is being initialised.
> > 
> > Note that sparse_early_usemap_alloc() does not use alloc_remap() like
> > sparse_early_mem_map_alloc(). The allocation required for the bitmap on x86,
> > the only architecture that uses alloc_remap is typically smaller than a cache
> > line. alloc_remap() pads out allocations to the cache size which would be
> > a needless waste.
> > 
> > Credit to Bob Picco for identifying the original problem and effecting a
> > fix for the SECTION_BLOCKFLAGS_BITS calculation. Credit to Andy Whitcroft
> > for devising the best way of allocating the bitmaps only when required for
> > the section.
> 
> SuperH allmodconfig blew up:
> 
> mm/sparse.c: In function `sparse_init':
> mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
> mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
> mm/sparse.c: In function `sparse_add_one_section':
> mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
> mm/sparse.c:553: warning: assignment makes pointer from integer without a cast

I'm looking at this now and getting a superh cross-compiler built to
build-test any fix. My first impression is that
sparse_early_usemap_alloc() needs to be defined whether
CONFIG_SPARSEMEM_VMEMMAP is set or not. Right now,
sparse_early_usemap_alloc() is only defined when it is set and it's not
clear why although "by accident" is the most likely explanation.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Mel Gorman]

On (24/07/07 22:01), Andrew Morton didst pronounce:
> On Tue, 13 Mar 2007 10:42:02 +0000 mel@skynet.ie (Mel Gorman) wrote:
> 
> > There are problems in the use of SPARSEMEM and pageblock flags that causes
> > problems on ia64.
> > 
> > <SNIP>
> 
> SuperH allmodconfig blew up:
> 
> mm/sparse.c: In function `sparse_init':
> mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
> mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
> mm/sparse.c: In function `sparse_add_one_section':
> mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
> mm/sparse.c:553: warning: assignment makes pointer from integer without a cast

This error is due to a bad interaction between
generic-virtual-memmap-support-for-sparsemem.patch and
fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch
. Functions that are needed whether CONFIG_SPARSEMEM_VMEMMAP is set are
not are depending on CONFIG_SPARSEMEM_VMEMMAP . This breaks on arch/sh
for example where SPARSEMEM may be set but not NUMA.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>

---
 sparse.c |   58 +++++++++++++++++++++++++++++-----------------------------
 1 file changed, 29 insertions(+), 29 deletions(-)


diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.23-rc1-mm1-clean/mm/sparse.c linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c
--- linux-2.6.23-rc1-mm1-clean/mm/sparse.c	2007-07-25 13:43:30.000000000 +0100
+++ linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c	2007-07-25 14:27:58.000000000 +0100
@@ -220,6 +220,35 @@ void *alloc_bootmem_high_node(pg_data_t 
 	return NULL;
 }
 
+static unsigned long usemap_size(void)
+{
+	unsigned long size_bytes;
+	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
+	size_bytes = roundup(size_bytes, sizeof(unsigned long));
+	return size_bytes;
+}
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static unsigned long *__kmalloc_section_usemap(void)
+{
+	return kmalloc(usemap_size(), GFP_KERNEL);
+}
+#endif /* CONFIG_MEMORY_HOTPLUG */
+
+static unsigned long *sparse_early_usemap_alloc(unsigned long pnum)
+{
+	unsigned long *usemap;
+	struct mem_section *ms = __nr_to_section(pnum);
+	int nid = sparse_early_nid(ms);
+
+	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
+	if (usemap)
+		return usemap;
+
+	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
+	return NULL;
+}
+
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 /*
  * Virtual Memory Map support
@@ -254,35 +283,6 @@ void *alloc_bootmem_high_node(pg_data_t 
  * 	require one PTE/TLB per PAGE_SIZE chunk of the virtual memory map.
  */
 
-static unsigned long usemap_size(void)
-{
-	unsigned long size_bytes;
- 	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
-	size_bytes = roundup(size_bytes, sizeof(unsigned long));
-	return size_bytes;
-}
-
-#ifdef CONFIG_MEMORY_HOTPLUG
-static unsigned long *__kmalloc_section_usemap(void)
-{
-	return kmalloc(usemap_size(), GFP_KERNEL);
-}
-#endif /* CONFIG_MEMORY_HOTPLUG */
-
-static unsigned long *sparse_early_usemap_alloc(unsigned long pnum)
-{
-	unsigned long *usemap;
-	struct mem_section *ms = __nr_to_section(pnum);
-	int nid = sparse_early_nid(ms);
-
-	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
-	if (usemap)
-		return usemap;
-
-	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
-	return NULL;
-}
-
 /*
  * Allocate a block of memory to be used to back the virtual memory map
  * or to back the page tables that are used to create the mapping.
-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Mel Gorman]

On (25/07/07 15:49), Mel Gorman didst pronounce:
> > SuperH allmodconfig blew up:
> > 
> > mm/sparse.c: In function `sparse_init':
> > mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
> > mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
> > mm/sparse.c: In function `sparse_add_one_section':
> > mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
> > mm/sparse.c:553: warning: assignment makes pointer from integer without a cast
> 
> This error is due to a bad interaction between
> generic-virtual-memmap-support-for-sparsemem.patch and
> fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch
> . Functions that are needed whether CONFIG_SPARSEMEM_VMEMMAP is set are
> not are depending on CONFIG_SPARSEMEM_VMEMMAP . This breaks on arch/sh
> for example where SPARSEMEM may be set but not NUMA.
> 

This patch only moves code and does not alter it. However, as SPARSEMEM
is set without NUMA, the code move generates a warning on SuperH because
NODE_DATA(nid) is a no-op. The following patch supresses the warning

Signed-off-by: Mel Gorman <mel@csn.ul.ie>

---
 sparse.c |    3 +++
 1 file changed, 3 insertions(+)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c linux-2.6.23-rc1-mm1-010-sh-sparsemem-fix-warning/mm/sparse.c
--- linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c	2007-07-25 14:27:58.000000000 +0100
+++ linux-2.6.23-rc1-mm1-010-sh-sparsemem-fix-warning/mm/sparse.c	2007-07-25 15:43:07.000000000 +0100
@@ -245,6 +245,9 @@ static unsigned long *sparse_early_usema
 	if (usemap)
 		return usemap;
 
+	/* Stupid: suppress gcc warning for SPARSEMEM && !NUMA */
+	nid = 0;
+
 	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
 	return NULL;
 }

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Andy Whitcroft]

Mel Gorman wrote:
> On (24/07/07 22:01), Andrew Morton didst pronounce:
>> On Tue, 13 Mar 2007 10:42:02 +0000 mel@skynet.ie (Mel Gorman) wrote:
>>
>>> There are problems in the use of SPARSEMEM and pageblock flags that causes
>>> problems on ia64.
>>>
>>> <SNIP>
>> SuperH allmodconfig blew up:
>>
>> mm/sparse.c: In function `sparse_init':
>> mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
>> mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
>> mm/sparse.c: In function `sparse_add_one_section':
>> mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
>> mm/sparse.c:553: warning: assignment makes pointer from integer without a cast
> 
> This error is due to a bad interaction between
> generic-virtual-memmap-support-for-sparsemem.patch and
> fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch
> . Functions that are needed whether CONFIG_SPARSEMEM_VMEMMAP is set are
> not are depending on CONFIG_SPARSEMEM_VMEMMAP . This breaks on arch/sh
> for example where SPARSEMEM may be set but not NUMA.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> 
> ---
>  sparse.c |   58 +++++++++++++++++++++++++++++-----------------------------
>  1 file changed, 29 insertions(+), 29 deletions(-)
> 
> 
> diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.23-rc1-mm1-clean/mm/sparse.c linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c
> --- linux-2.6.23-rc1-mm1-clean/mm/sparse.c	2007-07-25 13:43:30.000000000 +0100
> +++ linux-2.6.23-rc1-mm1-005-sh-sparsemem-fix/mm/sparse.c	2007-07-25 14:27:58.000000000 +0100
> @@ -220,6 +220,35 @@ void *alloc_bootmem_high_node(pg_data_t 
>  	return NULL;
>  }
>  
> +static unsigned long usemap_size(void)
> +{
> +	unsigned long size_bytes;
> +	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
> +	size_bytes = roundup(size_bytes, sizeof(unsigned long));
> +	return size_bytes;
> +}
> +
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +static unsigned long *__kmalloc_section_usemap(void)
> +{
> +	return kmalloc(usemap_size(), GFP_KERNEL);
> +}
> +#endif /* CONFIG_MEMORY_HOTPLUG */
> +
> +static unsigned long *sparse_early_usemap_alloc(unsigned long pnum)
> +{
> +	unsigned long *usemap;
> +	struct mem_section *ms = __nr_to_section(pnum);
> +	int nid = sparse_early_nid(ms);
> +
> +	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
> +	if (usemap)
> +		return usemap;
> +
> +	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
> +	return NULL;
> +}
> +
>  #ifdef CONFIG_SPARSEMEM_VMEMMAP
>  /*
>   * Virtual Memory Map support
> @@ -254,35 +283,6 @@ void *alloc_bootmem_high_node(pg_data_t 
>   * 	require one PTE/TLB per PAGE_SIZE chunk of the virtual memory map.
>   */
>  
> -static unsigned long usemap_size(void)
> -{
> -	unsigned long size_bytes;
> - 	size_bytes = roundup(SECTION_BLOCKFLAGS_BITS, 8) / 8;
> -	size_bytes = roundup(size_bytes, sizeof(unsigned long));
> -	return size_bytes;
> -}
> -
> -#ifdef CONFIG_MEMORY_HOTPLUG
> -static unsigned long *__kmalloc_section_usemap(void)
> -{
> -	return kmalloc(usemap_size(), GFP_KERNEL);
> -}
> -#endif /* CONFIG_MEMORY_HOTPLUG */
> -
> -static unsigned long *sparse_early_usemap_alloc(unsigned long pnum)
> -{
> -	unsigned long *usemap;
> -	struct mem_section *ms = __nr_to_section(pnum);
> -	int nid = sparse_early_nid(ms);
> -
> -	usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
> -	if (usemap)
> -		return usemap;
> -
> -	printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
> -	return NULL;
> -}
> -
>  /*
>   * Allocate a block of memory to be used to back the virtual memory map
>   * or to back the page tables that are used to create the mapping.

This also affects NUMA-Q in some SPARSEMEM configurations.  Applying
this fixes it up.

Looks very much like diff has dropped the stuff within my #ifdef
'incorrectly' and as such is a merge error.  This should probabally be
considered a fix to this patch:

fix-corruption-of-memmap-on-ia64-sparsemem-when-mem_section-is-not-a-power-of-2.patch

Acked-by: Andy Whitcroft <apw@shadowen.org>

-apw

Re: [PATCH] Fix corruption of memmap on IA64 SPARSEMEM when mem_section is not a power of 2

[Andrew Morton]

On Wed, 25 Jul 2007 13:55:02 +0100
mel@skynet.ie (Mel Gorman) wrote:

> > mm/sparse.c: In function `sparse_init':
> > mm/sparse.c:482: error: implicit declaration of function `sparse_early_usemap_alloc'
> > mm/sparse.c:482: warning: assignment makes pointer from integer without a cast
> > mm/sparse.c: In function `sparse_add_one_section':
> > mm/sparse.c:553: error: implicit declaration of function `__kmalloc_section_usemap'
> > mm/sparse.c:553: warning: assignment makes pointer from integer without a cast
> 
> I'm looking at this now and getting a superh cross-compiler built to
> build-test any fix. My first impression is that
> sparse_early_usemap_alloc() needs to be defined whether
> CONFIG_SPARSEMEM_VMEMMAP is set or not. Right now,
> sparse_early_usemap_alloc() is only defined when it is set and it's not
> clear why although "by accident" is the most likely explanation.
> 

Thanks.

There's an sh cross-compiler in http://userweb.kernel.org/~akpm/cross-compilers/,
btw.