Re: [PATCH 1/5] v2 Split the memory_block structure

Thanks for taking a look a this Kame, answers below...

-Nathan

On 07/15/2010 07:06 PM, KAMEZAWA Hiroyuki wrote:

On Thu, 15 Jul 2010 13:37:51 -0500
Nathan Fontenot [off-list ref] wrote:

quoted

Split the memory_block struct into a memory_block
struct to cover each sysfs directory and a new memory_block_section
struct for each memory section covered by the sysfs directory.
This change allows for creation of memory sysfs directories that
can span multiple memory sections.

This can be beneficial in that it can reduce the number of memory
sysfs directories created at boot.  This also allows different
architectures to define how many memory sections are covered by
a sysfs directory.

Signed-off-by: Nathan Fontenot <redacted>
---
 drivers/base/memory.c  |  222 ++++++++++++++++++++++++++++++++++---------------
 include/linux/memory.h |   11 +-
 2 files changed, 167 insertions(+), 66 deletions(-)

Index: linux-2.6/drivers/base/memory.c
===================================================================

--- linux-2.6.orig/drivers/base/memory.c	2010-07-15 08:48:41.000000000 -0500
+++ linux-2.6/drivers/base/memory.c	2010-07-15 09:55:54.000000000 -0500

@@ -28,6 +28,14 @@
 #include <asm/uaccess.h>
 
 #define MEMORY_CLASS_NAME	"memory"
+#define MIN_MEMORY_BLOCK_SIZE	(1 << SECTION_SIZE_BITS)
+
+static int sections_per_block;
+
+static inline int base_memory_block_id(int section_nr)
+{
+	return (section_nr / sections_per_block) * sections_per_block;
+}
 
 static struct sysdev_class memory_sysdev_class = {
 	.name = MEMORY_CLASS_NAME,

@@ -94,10 +102,9 @@
 }
 
 static void
-unregister_memory(struct memory_block *memory, struct mem_section *section)
+unregister_memory(struct memory_block *memory)
 {
 	BUG_ON(memory->sysdev.cls != &memory_sysdev_class);
-	BUG_ON(memory->sysdev.id != __section_nr(section));
 
 	/* drop the ref. we got in remove_memory_block() */
 	kobject_put(&memory->sysdev.kobj);

@@ -123,13 +130,20 @@
 static ssize_t show_mem_removable(struct sys_device *dev,
 			struct sysdev_attribute *attr, char *buf)
 {
+	struct memory_block *mem;
+	struct memory_block_section *mbs;
 	unsigned long start_pfn;
-	int ret;
-	struct memory_block *mem =
-		container_of(dev, struct memory_block, sysdev);
+	int ret = 1;
+
+	mem = container_of(dev, struct memory_block, sysdev);
+	mutex_lock(&mem->state_mutex);
 
-	start_pfn = section_nr_to_pfn(mem->phys_index);
-	ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
+	list_for_each_entry(mbs, &mem->sections, next) {
+		start_pfn = section_nr_to_pfn(mbs->phys_index);
+		ret &= is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
+	}
+
+	mutex_unlock(&mem->state_mutex);

Hmm, this means memory cab be offlined the while memory block section. Right ?
Please write this fact in patch description...
And Documentaion/memory_hotplug.txt as "From user's perspective, memory section
is not a unit of memory hotplug anymore".
And descirbe about a new rule.

You are correct.  A memory block is removable only if all of the memory
sections contained within the memory block are removable.

I will include a documentation patch with v3 of the patches to explain this
and to explain that memory add/remove operations are done on a per memory
block basis.

sorry about that.  I'm just using the default options with quilt.  I'll
play around with it to why this is happening.

quoted

 static int memory_block_change_state(struct memory_block *mem,
 		unsigned long to_state, unsigned long from_state_req)
 {
+	struct memory_block_section *mbs;
 	int ret = 0;
+
 	mutex_lock(&mem->state_mutex);
 
-	if (mem->state != from_state_req) {
-		ret = -EINVAL;
-		goto out;
+	list_for_each_entry(mbs, &mem->sections, next) {
+		if (mbs->state != from_state_req)
+			continue;
+
+		ret = memory_block_action(mbs, to_state);
+		if (ret)
+			break;
+	}
+
+	if (ret) {
+		list_for_each_entry(mbs, &mem->sections, next) {
+			if (mbs->state == from_state_req)
+				continue;
+
+			if (memory_block_action(mbs, to_state))
+				printk(KERN_ERR "Could not re-enable memory "
+				       "section %lx\n", mbs->phys_index);

Why re-enable only ? online->fail->offline never happens ?
If so, please add comment at least.

This should handle both conditions.  If we fail to move all of the memory
sections to the 'to_state', it puts all of the memory sections back to the
'from_state_req'.

BTW, is it guaranteed that all sections under a block has same state after
boot ?

Yes, during boot all memory sections are marked online.

quoted

+		}
 	}
 
-	ret = memory_block_action(mem, to_state);
 	if (!ret)
 		mem->state = to_state;
 
-out:
 	mutex_unlock(&mem->state_mutex);
 	return ret;
 }

@@ -260,20 +289,15 @@
 		struct sysdev_attribute *attr, const char *buf, size_t count)
 {
 	struct memory_block *mem;
-	unsigned int phys_section_nr;
 	int ret = -EINVAL;
 
 	mem = container_of(dev, struct memory_block, sysdev);
-	phys_section_nr = mem->phys_index;
-
-	if (!present_section_nr(phys_section_nr))
-		goto out;

I'm sorry but I couldn't remember why this check was necessary...

Not sure either, it appears that it is there to ensure that the memory
section we are trying to act on is actually present.

quoted

 	if (!strncmp(buf, "online", min((int)count, 6)))
 		ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
 	else if(!strncmp(buf, "offline", min((int)count, 7)))
 		ret = memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
-out:
+
 	if (ret)
 		return ret;
 	return count;

@@ -435,39 +459,6 @@
 	return 0;
 }
 
-static int add_memory_block(int nid, struct mem_section *section,
-			unsigned long state, enum mem_add_context context)
-{
-	struct memory_block *mem = kzalloc(sizeof(*mem), GFP_KERNEL);
-	unsigned long start_pfn;
-	int ret = 0;
-
-	if (!mem)
-		return -ENOMEM;
-
-	mem->phys_index = __section_nr(section);
-	mem->state = state;
-	mutex_init(&mem->state_mutex);
-	start_pfn = section_nr_to_pfn(mem->phys_index);
-	mem->phys_device = arch_get_memory_phys_device(start_pfn);
-
-	ret = register_memory(mem, section);
-	if (!ret)
-		ret = mem_create_simple_file(mem, phys_index);
-	if (!ret)
-		ret = mem_create_simple_file(mem, state);
-	if (!ret)
-		ret = mem_create_simple_file(mem, phys_device);
-	if (!ret)
-		ret = mem_create_simple_file(mem, removable);
-	if (!ret) {
-		if (context == HOTPLUG)
-			ret = register_mem_sect_under_node(mem, nid);
-	}
-
-	return ret;
-}
-

I don't say strongly but this kind of move-code should be done in another patch.

ok,  I will move the code move piece to a differnet patch.

quoted

 /*
  * For now, we have a linear search to go find the appropriate
  * memory_block corresponding to a particular phys_index. If

@@ -482,12 +473,13 @@
 	struct sys_device *sysdev;
 	struct memory_block *mem;
 	char name[sizeof(MEMORY_CLASS_NAME) + 9 + 1];
+	int block_id = base_memory_block_id(__section_nr(section));
 
 	/*
 	 * This only works because we know that section == sysdev->id
 	 * slightly redundant with sysdev_register()
 	 */
-	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, __section_nr(section));
+	sprintf(&name[0], "%s%d", MEMORY_CLASS_NAME, block_id);
 
 	kobj = kset_find_obj(&memory_sysdev_class.kset, name);
 	if (!kobj)

@@ -499,18 +491,98 @@
 	return mem;
 }
 
+static int add_mem_block_section(struct memory_block *mem,
+				 int section_nr, unsigned long state)
+{
+	struct memory_block_section *mbs;
+
+	mbs = kzalloc(sizeof(*mbs), GFP_KERNEL);
+	if (!mbs)
+		return -ENOMEM;
+
+	mbs->phys_index = section_nr;
+	mbs->state = state;
+
+	list_add(&mbs->next, &mem->sections);
+	return 0;
+}

Doesn't this "sections" need to be sorted ? Hmm.

We could, but I cannot think of anything we gain by sorting it.

quoted

+
+static int add_memory_block(int nid, struct mem_section *section,
+			unsigned long state, enum mem_add_context context)
+{
+	struct memory_block *mem;
+	int ret = 0;
+
+	mem = find_memory_block(section);
+	if (!mem) {
+		unsigned long start_pfn;
+
+		mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+		if (!mem)
+			return -ENOMEM;
+
+		mem->state = state;
+		mutex_init(&mem->state_mutex);
+		start_pfn = section_nr_to_pfn(__section_nr(section));
+		mem->phys_device = arch_get_memory_phys_device(start_pfn);
+		INIT_LIST_HEAD(&mem->sections);
+
+		mutex_lock(&mem->state_mutex);
+
+		ret = register_memory(mem, section);
+		if (!ret)
+			ret = mem_create_simple_file(mem, phys_index);
+		if (!ret)
+			ret = mem_create_simple_file(mem, state);
+		if (!ret)
+			ret = mem_create_simple_file(mem, phys_device);
+		if (!ret)
+			ret = mem_create_simple_file(mem, removable);
+		if (!ret) {
+			if (context == HOTPLUG)
+				ret = register_mem_sect_under_node(mem, nid);
+		}
+	} else {
+		kobject_put(&mem->sysdev.kobj);
+		mutex_lock(&mem->state_mutex);
+	}
+
+	if (!ret)
+		ret = add_mem_block_section(mem, __section_nr(section), state);
+
+	mutex_unlock(&mem->state_mutex);
+	return ret;
+}
+
 int remove_memory_block(unsigned long node_id, struct mem_section *section,
 		int phys_device)
 {
 	struct memory_block *mem;
+	struct memory_block_section *mbs, *tmp;
+	int section_nr = __section_nr(section);
 
 	mem = find_memory_block(section);
-	unregister_mem_sect_under_nodes(mem);
-	mem_remove_simple_file(mem, phys_index);
-	mem_remove_simple_file(mem, state);
-	mem_remove_simple_file(mem, phys_device);
-	mem_remove_simple_file(mem, removable);
-	unregister_memory(mem, section);
+	mutex_lock(&mem->state_mutex);
+
+	/* remove the specified section */
+	list_for_each_entry_safe(mbs, tmp, &mem->sections, next) {
+		if (mbs->phys_index == section_nr) {
+			list_del(&mbs->next);
+			kfree(mbs);
+		}
+	}
+
+	mutex_unlock(&mem->state_mutex);
+
+	if (list_empty(&mem->sections)) {
+		unregister_mem_sect_under_nodes(mem);
+		mem_remove_simple_file(mem, phys_index);
+		mem_remove_simple_file(mem, state);
+		mem_remove_simple_file(mem, phys_device);
+		mem_remove_simple_file(mem, removable);
+		unregister_memory(mem);
+		kfree(mem);
+	}
 
 	return 0;
 }

@@ -532,6 +604,24 @@
 	return remove_memory_block(0, section, 0);
 }
 
+u32 __weak memory_block_size(void)
+{
+	return MIN_MEMORY_BLOCK_SIZE;
+}
+
+static u32 get_memory_block_size(void)
+{
+	u32 blk_sz;
+
+	blk_sz = memory_block_size();
+
+	/* Validate blk_sz is a power of 2 and not less than section size */
+	if ((blk_sz & (blk_sz - 1)) || (blk_sz < MIN_MEMORY_BLOCK_SIZE))
+		blk_sz = MIN_MEMORY_BLOCK_SIZE;
+
+	return blk_sz;
+}
+
 /*
  * Initialize the sysfs support for memory devices...
  */

@@ -540,12 +630,16 @@
 	unsigned int i;
 	int ret;
 	int err;
+	int block_sz;
 
 	memory_sysdev_class.kset.uevent_ops = &memory_uevent_ops;
 	ret = sysdev_class_register(&memory_sysdev_class);
 	if (ret)
 		goto out;
 
+	block_sz = get_memory_block_size();
+	sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
+
 	/*
 	 * Create entries for memory sections that were found
 	 * during boot and have been initialized

Index: linux-2.6/include/linux/memory.h
===================================================================

--- linux-2.6.orig/include/linux/memory.h	2010-07-15 08:48:41.000000000 -0500
+++ linux-2.6/include/linux/memory.h	2010-07-15 09:54:06.000000000 -0500

@@ -19,9 +19,15 @@
 #include <linux/node.h>
 #include <linux/compiler.h>
 #include <linux/mutex.h>
+#include <linux/list.h>
 
-struct memory_block {
+struct memory_block_section {
+	unsigned long state;
 	unsigned long phys_index;
+	struct list_head next;
+};
+
+struct memory_block {
 	unsigned long state;
 	/*
 	 * This serializes all state change requests.  It isn't

@@ -34,6 +40,7 @@
 	void *hw;			/* optional pointer to fw/hw data */
 	int (*phys_callback)(struct memory_block *);
 	struct sys_device sysdev;
+	struct list_head sections;
 };
 
 int arch_get_memory_phys_device(unsigned long start_pfn);

@@ -113,7 +120,7 @@
 extern int remove_memory_block(unsigned long, struct mem_section *, int);
 extern int memory_notify(unsigned long val, void *v);
 extern int memory_isolate_notify(unsigned long val, void *v);
-extern struct memory_block *find_memory_block(unsigned long);
+extern struct memory_block *find_memory_block(struct mem_section *);
 extern int memory_is_hidden(struct mem_section *);
 #define CONFIG_MEM_BLOCK_SIZE	(PAGES_PER_SECTION<<PAGE_SHIFT)
 enum mem_add_context { BOOT, HOTPLUG };

Okay, please go ahead. But my 1st impression is that IBM should increase ppc's
SECTION_SIZE ;)

Thanks,
-Kame