[patch -mm] mm: slab allocate memory section nodemask for large systems

[patch -mm] mm: slab allocate memory section nodemask for large systems

[David Rientjes]

Nodemasks should not be allocated on the stack for large systems (when it
is larger than 256 bytes) since there is a threat of overflow.

This patch causes the unregister_mem_sect_under_nodes() nodemask to be
allocated on the stack for smaller systems and be allocated by slab for
larger systems.

GFP_KERNEL is used since remove_memory_block() can block.

Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Alex Chiang <achiang@hp.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 drivers/base/node.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -363,12 +363,16 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 /* unregister memory section under all nodes that it spans */
 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 {
-	nodemask_t unlinked_nodes;
+	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
 
-	if (!mem_blk)
+	if (!mem_blk) {
+		NODEMASK_FREE(unlinked_nodes);
 		return -EFAULT;
-	nodes_clear(unlinked_nodes);
+	}
+	if (!unlinked_nodes)
+		return -ENOMEM;
+	nodes_clear(*unlinked_nodes);
 	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
@@ -379,13 +383,14 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 			continue;
 		if (!node_online(nid))
 			continue;
-		if (node_test_and_set(nid, unlinked_nodes))
+		if (node_test_and_set(nid, *unlinked_nodes))
 			continue;
 		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 			 kobject_name(&mem_blk->sysdev.kobj));
 		sysfs_remove_link(&mem_blk->sysdev.kobj,
 			 kobject_name(&node_devices[nid].sysdev.kobj));
 	}
+	NODEMASK_FREE(unlinked_nodes);
 	return 0;
 }
 

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[Gary Hade]

Hi David,

On Tue, Nov 17, 2009 at 04:19:30PM -0800, David Rientjes wrote:
> Nodemasks should not be allocated on the stack for large systems (when it
> is larger than 256 bytes) since there is a threat of overflow.
> 
> This patch causes the unregister_mem_sect_under_nodes() nodemask to be
> allocated on the stack for smaller systems and be allocated by slab for
> larger systems.

I notice that there are many other functions that always allocate
nodemask_t objects on the stack.  In addition to several that add
a single instance to the stack, cpuset_attach() in kernel/cpuset.c
adds 2 instances and all that are created by using SYSCALL_DEFINE4()
in mm/mempolicy.c add 3 instances.  Are there plans to correct the
other functions as well or is there something about
unregister_mem_sect_under_nodes() that makes it more likely to
cause stack overflows than the others?

Gary

-- 
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503  IBM T/L: 775-4503
garyhade@us.ibm.com
http://www.ibm.com/linux/ltc

[PATCH v2 0/5] mm: modest useability enhancements for node sysfs attrs

[Alex Chiang]

This is v2 of the series.

The last patch in this series is dependent upon the documentation patch
series that I just sent out a few moments ago:

	http://thread.gmane.org/gmane.linux.kernel/905018

Thanks,
/ac


v1 -> v2: http://thread.gmane.org/gmane.linux.kernel.mm/40084/
	Address David Rientjes's comments
	- check return value of sysfs_create_link in register_cpu_under_node
	- do /not/ convert [un]register_cpu_under_node to return void, since
	  sparse starts whinging if you ignore sysfs_create_link()'s return
	  value and working around sparse makes the code ugly
	- adjust documentation

	Added S390 maintainers to cc: for patch [1/5] as per Kame-san's
	suggestion. S390 may map a memory section to more than one node,
	causing this series to break.

---

Alex Chiang (5):
      mm: add numa node symlink for memory section in sysfs
      mm: refactor register_cpu_under_node()
      mm: refactor unregister_cpu_under_node()
      mm: add numa node symlink for cpu devices in sysfs
      Documentation: ABI: /sys/devices/system/cpu/cpu#/node


 Documentation/ABI/testing/sysfs-devices-memory     |   14 ++++-
 Documentation/ABI/testing/sysfs-devices-system-cpu |   15 +++++
 Documentation/memory-hotplug.txt                   |   11 ++--
 drivers/base/node.c                                |   58 ++++++++++++++------
 4 files changed, 77 insertions(+), 21 deletions(-)

[PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[Alex Chiang]

Commit c04fc586c (mm: show node to memory section relationship with
symlinks in sysfs) created symlinks from nodes to memory sections, e.g.

/sys/devices/system/node/node1/memory135 -> ../../memory/memory135

If you're examining the memory section though and are wondering what
node it might belong to, you can find it by grovelling around in
sysfs, but it's a little cumbersome.

Add a reverse symlink for each memory section that points back to the
node to which it belongs.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Alex Chiang <achiang@hp.com>
---

 Documentation/ABI/testing/sysfs-devices-memory |   14 +++++++++++++-
 Documentation/memory-hotplug.txt               |   11 +++++++----
 drivers/base/node.c                            |   11 ++++++++++-
 3 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
index 9fe91c0..bf1627b 100644
--- a/Documentation/ABI/testing/sysfs-devices-memory
+++ b/Documentation/ABI/testing/sysfs-devices-memory
@@ -60,6 +60,19 @@ Description:
 Users:		hotplug memory remove tools
 		https://w3.opensource.ibm.com/projects/powerpc-utils/
 
+
+What:		/sys/devices/system/memoryX/nodeY
+Date:		October 2009
+Contact:	Linux Memory Management list <linux-mm@kvack.org>
+Description:
+		When CONFIG_NUMA is enabled, a symbolic link that
+		points to the corresponding NUMA node directory.
+
+		For example, the following symbolic link is created for
+		memory section 9 on node0:
+		/sys/devices/system/memory/memory9/node0 -> ../../node/node0
+
+
 What:		/sys/devices/system/node/nodeX/memoryY
 Date:		September 2008
 Contact:	Gary Hade <garyhade@us.ibm.com>
@@ -70,4 +83,3 @@ Description:
 		memory section directory.  For example, the following symbolic
 		link is created for memory section 9 on node0.
 		/sys/devices/system/node/node0/memory9 -> ../../memory/memory9
-
diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index bbc8a6a..57e7e9c 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -160,12 +160,15 @@ Under each section, you can see 4 files.
 NOTE:
   These directories/files appear after physical memory hotplug phase.
 
-If CONFIG_NUMA is enabled the
-/sys/devices/system/memory/memoryXXX memory section
-directories can also be accessed via symbolic links located in
-the /sys/devices/system/node/node* directories.  For example:
+If CONFIG_NUMA is enabled the memoryXXX/ directories can also be accessed
+via symbolic links located in the /sys/devices/system/node/node* directories.
+
+For example:
 /sys/devices/system/node/node0/memory9 -> ../../memory/memory9
 
+A backlink will also be created:
+/sys/devices/system/memory/memory9/node0 -> ../../node/node0
+
 --------------------------------
 4. Physical memory hot-add phase
 --------------------------------
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 1fe5536..3108b21 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -268,6 +268,7 @@ static int get_nid_for_pfn(unsigned long pfn)
 /* register memory section under specified node if it spans that node */
 int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 {
+	int ret;
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
 
 	if (!mem_blk)
@@ -284,9 +285,15 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 			continue;
 		if (page_nid != nid)
 			continue;
-		return sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
+		ret = sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
 					&mem_blk->sysdev.kobj,
 					kobject_name(&mem_blk->sysdev.kobj));
+		if (ret)
+			return ret;
+
+		return sysfs_create_link_nowarn(&mem_blk->sysdev.kobj,
+				&node_devices[nid].sysdev.kobj,
+				kobject_name(&node_devices[nid].sysdev.kobj));
 	}
 	/* mem section does not span the specified node */
 	return 0;
@@ -315,6 +322,8 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 			continue;
 		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 			 kobject_name(&mem_blk->sysdev.kobj));
+		sysfs_remove_link(&mem_blk->sysdev.kobj,
+			 kobject_name(&node_devices[nid].sysdev.kobj));
 	}
 	return 0;
 }

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[David Rientjes]

On Wed, 21 Oct 2009, Alex Chiang wrote:

> Commit c04fc586c (mm: show node to memory section relationship with
> symlinks in sysfs) created symlinks from nodes to memory sections, e.g.
> 
> /sys/devices/system/node/node1/memory135 -> ../../memory/memory135
> 
> If you're examining the memory section though and are wondering what
> node it might belong to, you can find it by grovelling around in
> sysfs, but it's a little cumbersome.
> 
> Add a reverse symlink for each memory section that points back to the
> node to which it belongs.
> 
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Gary Hade <garyhade@us.ibm.com>
> Cc: Badari Pulavarty <pbadari@us.ibm.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Signed-off-by: Alex Chiang <achiang@hp.com>

Acked-by: David Rientjes <rientjes@google.com>

Very helpful backlinks to memory section nodes even though I have lots of 
memory directories on some of my test machines :)

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[Alex Chiang]

Thank you for ACKing, David.

S390 guys, I cc'ed you on this patch because I heard a rumour
that your memory sections may belong to more than one NUMA node?
Is that true? If so, how would you like me to handle that
situation?

Any comments on this patch series would be appreciated.

Thanks.
/ac

* David Rientjes <rientjes@google.com>:
> On Wed, 21 Oct 2009, Alex Chiang wrote:
> 
> > Commit c04fc586c (mm: show node to memory section relationship with
> > symlinks in sysfs) created symlinks from nodes to memory sections, e.g.
> > 
> > /sys/devices/system/node/node1/memory135 -> ../../memory/memory135
> > 
> > If you're examining the memory section though and are wondering what
> > node it might belong to, you can find it by grovelling around in
> > sysfs, but it's a little cumbersome.
> > 
> > Add a reverse symlink for each memory section that points back to the
> > node to which it belongs.
> > 
> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> > Cc: Gary Hade <garyhade@us.ibm.com>
> > Cc: Badari Pulavarty <pbadari@us.ibm.com>
> > Cc: Ingo Molnar <mingo@elte.hu>
> > Signed-off-by: Alex Chiang <achiang@hp.com>
> 
> Acked-by: David Rientjes <rientjes@google.com>
> 
> Very helpful backlinks to memory section nodes even though I have lots of 
> memory directories on some of my test machines :)

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[David Rientjes]

On Tue, 27 Oct 2009, Alex Chiang wrote:

> Thank you for ACKing, David.
> 
> S390 guys, I cc'ed you on this patch because I heard a rumour
> that your memory sections may belong to more than one NUMA node?
> Is that true? If so, how would you like me to handle that
> situation?
> 

You're referring to how unregister_mem_sect_under_nodes() should be 
handled, right?  register_mem_sect_under_node() already looks supported by 
your patch.

Since the unregister function includes a plural "nodes," I assume that 
it's possible for hotplug to register a memory section to more than one 
node.  That's probably lacking on x86 currently, however, because we lack 
node hotplug.

I'd suggest a similiar iteration through pfn's that the register function 
does checking for multiple nodes and then removing the link from all 
applicable node_devices kobj when unregistering.

Maybe one of the s390 maintainers will test that?

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[Heiko Carstens]

On Tue, Oct 27, 2009 at 02:27:56PM -0700, David Rientjes wrote:
> On Tue, 27 Oct 2009, Alex Chiang wrote:
> 
> > Thank you for ACKing, David.
> > 
> > S390 guys, I cc'ed you on this patch because I heard a rumour
> > that your memory sections may belong to more than one NUMA node?
> > Is that true? If so, how would you like me to handle that
> > situation?
> > 
> 
> You're referring to how unregister_mem_sect_under_nodes() should be 
> handled, right?  register_mem_sect_under_node() already looks supported by 
> your patch.
> 
> Since the unregister function includes a plural "nodes," I assume that 
> it's possible for hotplug to register a memory section to more than one 
> node.  That's probably lacking on x86 currently, however, because we lack 
> node hotplug.
> 
> I'd suggest a similiar iteration through pfn's that the register function 
> does checking for multiple nodes and then removing the link from all 
> applicable node_devices kobj when unregistering.
> 
> Maybe one of the s390 maintainers will test that?

The short answer is: s390 doesn't support NUMA, because the hardware doesn't
tell us to which node (book in s390 terms) a memory range belongs to.

Memory layout for a logical partition is striped: first x mbyte belong to
node 0, next x mbyte belong to node 1, etc...

Also, since there is always a hypervisor running below Linux I don't think
it would make too much sense if we would know to which node a piece of
memory belongs to: if the hypervisor decides to schedule a virtual cpu of
a logical partition to a different node then what?

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[David Rientjes]

On Wed, 28 Oct 2009, Heiko Carstens wrote:

> The short answer is: s390 doesn't support NUMA, because the hardware doesn't
> tell us to which node (book in s390 terms) a memory range belongs to.
> 
> Memory layout for a logical partition is striped: first x mbyte belong to
> node 0, next x mbyte belong to node 1, etc...
> 
> Also, since there is always a hypervisor running below Linux I don't think
> it would make too much sense if we would know to which node a piece of
> memory belongs to: if the hypervisor decides to schedule a virtual cpu of
> a logical partition to a different node then what?
> 

Ok, so the patchset is a no-op for s390 since it only utilizes the 
!CONFIG_NUMA code.

Alex, I think the safest thing to do in unregister_mem_sect_under_nodes() 
is to iterate though the section pfns and remove links to the node_device 
kobjs for all the distinct pfn_to_nid()'s that it encounters.

Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs

[Alex Chiang]

* David Rientjes <rientjes@google.com>:
> 
> Alex, I think the safest thing to do in unregister_mem_sect_under_nodes() 
> is to iterate though the section pfns and remove links to the node_device 
> kobjs for all the distinct pfn_to_nid()'s that it encounters.

Am I not understanding the code? It looks like we do this
already...

/* unregister memory section under all nodes that it spans */
int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
{
	nodemask_t unlinked_nodes;
	unsigned long pfn, sect_start_pfn, sect_end_pfn;

	if (!mem_blk)
		return -EFAULT;
	nodes_clear(unlinked_nodes);
	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
		int nid;

		nid = get_nid_for_pfn(pfn);
		if (nid < 0)
			continue;
		if (!node_online(nid))
			continue;
		if (node_test_and_set(nid, unlinked_nodes))
			continue;
		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
			 kobject_name(&mem_blk->sysdev.kobj));
		sysfs_remove_link(&mem_blk->sysdev.kobj,
			 kobject_name(&node_devices[nid].sysdev.kobj));
	}
	return 0;
}

Thanks,
/ac

[patch -mm] mm: slab allocate memory section nodemask for large systems

[David Rientjes]

On Wed, 28 Oct 2009, Alex Chiang wrote:

> Am I not understanding the code? It looks like we do this
> already...
> 
> /* unregister memory section under all nodes that it spans */
> int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
> {
> 	nodemask_t unlinked_nodes;
> 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
> 
> 	if (!mem_blk)
> 		return -EFAULT;
> 	nodes_clear(unlinked_nodes);
> 	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
> 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
> 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
> 		int nid;
> 
> 		nid = get_nid_for_pfn(pfn);
> 		if (nid < 0)
> 			continue;
> 		if (!node_online(nid))
> 			continue;
> 		if (node_test_and_set(nid, unlinked_nodes))
> 			continue;
> 		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
> 			 kobject_name(&mem_blk->sysdev.kobj));
> 		sysfs_remove_link(&mem_blk->sysdev.kobj,
> 			 kobject_name(&node_devices[nid].sysdev.kobj));
> 	}
> 	return 0;
> }
> 

That shound be sufficient with the exception that allocating nodemask_t 
on the stack is usually dangerous because it can be extremely large; we 
typically use NODEMASK_ALLOC() for such code.  It's had some changes in 
-mm, but since this patchset will likely be going through that tree anyway 
we can fix it now with the patch below.

Otherwise, it looks like the iteration is already there and will remove 
links for memory sections bound to multiple nodes if they exist through 
hotplug.



mm: slab allocate memory section nodemask for large systems

Nodemasks should not be allocated on the stack for large systems (when it
is larger than 256 bytes) since there is a threat of overflow.

This patch causes the unregister_mem_sect_under_nodes() nodemask to be
allocated on the stack for smaller systems and be allocated by slab for
larger systems.

GFP_KERNEL is used since remove_memory_block() can block.

Cc: Gary Hade <garyhade@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 Depends on NODEMASK_ALLOC() changes currently present only in -mm.

 drivers/base/node.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -363,12 +363,14 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 /* unregister memory section under all nodes that it spans */
 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 {
-	nodemask_t unlinked_nodes;
+	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
 
-	if (!mem_blk)
+	if (!mem_blk) {
+		NODEMASK_FREE(unlinked_nodes);
 		return -EFAULT;
-	nodes_clear(unlinked_nodes);
+	}
+	nodes_clear(*unlinked_nodes);
 	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
@@ -379,13 +381,14 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 			continue;
 		if (!node_online(nid))
 			continue;
-		if (node_test_and_set(nid, unlinked_nodes))
+		if (node_test_and_set(nid, *unlinked_nodes))
 			continue;
 		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 			 kobject_name(&mem_blk->sysdev.kobj));
 		sysfs_remove_link(&mem_blk->sysdev.kobj,
 			 kobject_name(&node_devices[nid].sysdev.kobj));
 	}
+	NODEMASK_FREE(unlinked_nodes);
 	return 0;
 }
 

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[Alex Chiang]

Hi Andrew,

* David Rientjes <rientjes@google.com>:
> On Wed, 28 Oct 2009, Alex Chiang wrote:
> 
> > Am I not understanding the code? It looks like we do this
> > already...
> > 
> > /* unregister memory section under all nodes that it spans */
> > int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
> > {
> > 	nodemask_t unlinked_nodes;
> > 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
> > 
> > 	if (!mem_blk)
> > 		return -EFAULT;
> > 	nodes_clear(unlinked_nodes);
> > 	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
> > 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
> > 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
> > 		int nid;
> > 
> > 		nid = get_nid_for_pfn(pfn);
> > 		if (nid < 0)
> > 			continue;
> > 		if (!node_online(nid))
> > 			continue;
> > 		if (node_test_and_set(nid, unlinked_nodes))
> > 			continue;
> > 		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
> > 			 kobject_name(&mem_blk->sysdev.kobj));
> > 		sysfs_remove_link(&mem_blk->sysdev.kobj,
> > 			 kobject_name(&node_devices[nid].sysdev.kobj));
> > 	}
> > 	return 0;
> > }
> > 
> 
> That shound be sufficient with the exception that allocating nodemask_t 
> on the stack is usually dangerous because it can be extremely large; we 
> typically use NODEMASK_ALLOC() for such code.  It's had some changes in 
> -mm, but since this patchset will likely be going through that tree anyway 
> we can fix it now with the patch below.
> 
> Otherwise, it looks like the iteration is already there and will remove 
> links for memory sections bound to multiple nodes if they exist through 
> hotplug.

Any comments on this patch series?

Turns out that Kame-san's fear about a memory section spanning
several nodes on certain architectures (S390) isn't really
applicable and even if it were, we have code to handle situation
anyway.

Kame-san was generally supportive of these convenience symlinks
although he did not give a formal ACK.

David has given an ACK on the two patches that do real work, as
well as supplied the below patch.

I can respin this series once more, including David's Acked-by:
and adding his patch if that makes life easier for you.

Thanks,
/ac


> mm: slab allocate memory section nodemask for large systems
> 
> Nodemasks should not be allocated on the stack for large systems (when it
> is larger than 256 bytes) since there is a threat of overflow.
> 
> This patch causes the unregister_mem_sect_under_nodes() nodemask to be
> allocated on the stack for smaller systems and be allocated by slab for
> larger systems.
> 
> GFP_KERNEL is used since remove_memory_block() can block.
> 
> Cc: Gary Hade <garyhade@us.ibm.com>
> Cc: Badari Pulavarty <pbadari@us.ibm.com>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
>  Depends on NODEMASK_ALLOC() changes currently present only in -mm.
> 
>  drivers/base/node.c |   11 +++++++----
>  1 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -363,12 +363,14 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
>  /* unregister memory section under all nodes that it spans */
>  int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
>  {
> -	nodemask_t unlinked_nodes;
> +	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
>  	unsigned long pfn, sect_start_pfn, sect_end_pfn;
>  
> -	if (!mem_blk)
> +	if (!mem_blk) {
> +		NODEMASK_FREE(unlinked_nodes);
>  		return -EFAULT;
> -	nodes_clear(unlinked_nodes);
> +	}
> +	nodes_clear(*unlinked_nodes);
>  	sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
>  	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
>  	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
> @@ -379,13 +381,14 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
>  			continue;
>  		if (!node_online(nid))
>  			continue;
> -		if (node_test_and_set(nid, unlinked_nodes))
> +		if (node_test_and_set(nid, *unlinked_nodes))
>  			continue;
>  		sysfs_remove_link(&node_devices[nid].sysdev.kobj,
>  			 kobject_name(&mem_blk->sysdev.kobj));
>  		sysfs_remove_link(&mem_blk->sysdev.kobj,
>  			 kobject_name(&node_devices[nid].sysdev.kobj));
>  	}
> +	NODEMASK_FREE(unlinked_nodes);
>  	return 0;
>  }
>  
> 

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[David Rientjes]

On Mon, 2 Nov 2009, Alex Chiang wrote:

> Any comments on this patch series?
> 
> Turns out that Kame-san's fear about a memory section spanning
> several nodes on certain architectures (S390) isn't really
> applicable and even if it were, we have code to handle situation
> anyway.
> 
> Kame-san was generally supportive of these convenience symlinks
> although he did not give a formal ACK.
> 
> David has given an ACK on the two patches that do real work, as
> well as supplied the below patch.
> 
> I can respin this series once more, including David's Acked-by:
> and adding his patch if that makes life easier for you.
> 

It's probably in Andrew's queue after getting back from the kernel summit, 
it would be best to wait a week or so.

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[Andrew Morton]

On Mon, 2 Nov 2009 13:47:26 -0700
Alex Chiang <achiang@hp.com> wrote:

> I can respin this series once more, including David's Acked-by:
> and adding his patch if that makes life easier for you.

Yes, please redo and resend.

The prerequisite Documentation/ patches are a bit of a mess - some have
been cherrypicked into Greg's tree I believe and some haven't.  So
please also send out whatever is needed to bring linux-next up to date.

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[David Rientjes]

On Tue, 10 Nov 2009, Andrew Morton wrote:

> The prerequisite Documentation/ patches are a bit of a mess - some have
> been cherrypicked into Greg's tree I believe and some haven't.  So
> please also send out whatever is needed to bring linux-next up to date.
> 

I'm not aware of any prerequisites for this patchset, Alex's documentation 
changes have already been merged by Linus.

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[Alex Chiang]

* David Rientjes <rientjes@google.com>:
> On Tue, 10 Nov 2009, Andrew Morton wrote:
> 
> > The prerequisite Documentation/ patches are a bit of a mess - some have
> > been cherrypicked into Greg's tree I believe and some haven't.  So
> > please also send out whatever is needed to bring linux-next up to date.

Thanks, I'll respin.

> I'm not aware of any prerequisites for this patchset, Alex's documentation 
> changes have already been merged by Linus.

Correct. So I'll respin this series against... Linus's tree? Or
maybe mmotm? Please advise.

Thanks,
/ac

Re: [patch -mm] mm: slab allocate memory section nodemask for large systems

[Andrew Morton]

On Tue, 10 Nov 2009 14:26:29 -0700
Alex Chiang <achiang@hp.com> wrote:

> > I'm not aware of any prerequisites for this patchset, Alex's documentation 
> > changes have already been merged by Linus.
> 
> Correct. So I'll respin this series against... Linus's tree? Or
> maybe mmotm? Please advise.

It appears that Linus's tree will be an OK base.