Subject: Re: [PATCH 1/7] Split the memory_block structure

From: Nathan Fontenot <[email-masked]>
Date: Tue, 13 Jul 2010 10:44:10 -0500

Thanks for the review, answers below...

-Nathan

On 07/13/2010 01:18 AM, KAMEZAWA Hiroyuki wrote:
> 
> plz cc linux-mm in the next time...
> And please incudes updates for Documentation/memory-hotplug.txt.
> 

will do.
> 
> On Mon, 12 Jul 2010 10:42:06 -0500
> Nathan Fontenot <[email-masked]> wrote:
> 
>> This patch splits 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 also updates the routine handling memory_block creation
>> and manipulation to use these updated structures.
>>
> 
> Could you clarify the number of memory_block_section per memory_block ?

The default number of memory_block_sections per memory block is 1.  The
memory_block_size() routine (defined as __weak) sets the size of the
memory block, and thus the number of memory_block_sections.

The current view of memory in sysfs where each directory covers a single
memory section should still hold for everyone, unless a arch defines
their own memory_section_size routine to alter the behavior.

> 
> 
>> Signed -off-by: Nathan Fontenot <[email-masked]>
>> ---
>>  drivers/base/memory.c  |  228 +++++++++++++++++++++++++++++++++++--------------
>>  include/linux/memory.h |   11 +-
>>  2 files changed, 172 insertions(+), 67 deletions(-)
>>
>> Index: linux-2.6/drivers/base/memory.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/base/memory.c	2010-07-08 11:27:21.000000000 -0500
>> +++ linux-2.6/drivers/base/memory.c	2010-07-09 14:23:09.000000000 -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;
>> +
> some default value, plz. Does this can be determined only by .config ?

The default is 1.  This is determined in the get_memory_block_size() which
is called from the memory sysfs init routine.

> 
> 
>> +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)
>>  {
>> -	unsigned long start_pfn;
>> -	int ret;
>> -	struct memory_block *mem =
>> -		container_of(dev, struct memory_block, sysdev);
>> +	struct list_head *pos, *tmp;
>> +	struct memory_block *mem;
>> +	int ret = 1;
>> +
>> +	mem = container_of(dev, struct memory_block, sysdev);
>> +	list_for_each_safe(pos, tmp, &mem->sections) {
>> +		struct memory_block_section *mbs;
>> +		unsigned long start_pfn;
>> +
>> +		mbs = list_entry(pos, struct memory_block_section, next);
> 
> list_for_each_entry ?

I went with list_for_each_safe() here since I am not holding the mutex
while walking the list.  Perhaps this should be changed to take the
mutex and use list_for_each_entry().

> 
> 
> 
>> +		start_pfn = section_nr_to_pfn(mbs->phys_index);
>> +		ret &= is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
>> +	}
> 
> Hmm, them, only when the whole memory block is removable, it's shown as
> removable. Right ?
> Does it meets ppc guy's requirements ?

Yes, and yes.

> 
>>  
>> -	start_pfn = section_nr_to_pfn(mem->phys_index);
>> -	ret = is_mem_section_removable(start_pfn, PAGES_PER_SECTION);
>>  	return sprintf(buf, "%d\n", ret);
>>  }
> 
> Hmm...can't you print removable information as bitmap, here ?
> overkill ?

We could print it as a bitmap, but I think it would be overkill.  The
memory add/remove routines work on a memory_block such that all
memory_block_sections in the memory_block are added/removed as a whole.
Given this, I figured we only needed to know if the entire memory_block
is removable.

> 
> 
>>  
>> @@ -182,16 +196,16 @@
>>   * OK to have direct references to sparsemem variables in here.
>>   */
>>  static int
>> -memory_block_action(struct memory_block *mem, unsigned long action)
>> +memory_block_action(struct memory_block_section *mbs, unsigned long action)
>>  {
>>  	int i;
>>  	unsigned long psection;
>>  	unsigned long start_pfn, start_paddr;
>>  	struct page *first_page;
>>  	int ret;
>> -	int old_state = mem->state;
>> ot-option-to-disable-memory-hotplug.patch
>> +	int old_state = mbs->state;
> 
> Where is this noise from ?

Yuck!  I'll take a look.  That shouldn't be there obviously.

> 
>>  
>> -	psection = mem->phys_index;
>> +	psection = mbs->phys_index;
>>  	first_page = pfn_to_page(psection << PFN_SECTION_SHIFT);
>>  
>>  	/*
>> @@ -217,18 +231,18 @@
>>  			ret = online_pages(start_pfn, PAGES_PER_SECTION);
>>  			break;
>>  		case MEM_OFFLINE:
>> -			mem->state = MEM_GOING_OFFLINE;
>> +			mbs->state = MEM_GOING_OFFLINE;
>>  			start_paddr = page_to_pfn(first_page) << PAGE_SHIFT;
>>  			ret = remove_memory(start_paddr,
>>  					    PAGES_PER_SECTION << PAGE_SHIFT);
>>  			if (ret) {
>> -				mem->state = old_state;
>> +				mbs->state = old_state;
>>  				break;
>>  			}
>>  			break;
>>  		default:
>>  			WARN(1, KERN_WARNING "%s(%p, %ld) unknown action: %ld\n",
>> -					__func__, mem, action, action);
>> +					__func__, mbs, action, action);
>>  			ret = -EINVAL;
>>  	}
>>  
>> @@ -238,19 +252,40 @@
>>  static int memory_block_change_state(struct memory_block *mem,
>>  		unsigned long to_state, unsigned long from_state_req)
>>  {
>> +	struct memory_block_section *mbs;
>> +	struct list_head *pos;
>>  	int ret = 0;
>> +
>>  	mutex_lock(&mem->state_mutex);
>>  
>> -	if (mem->state != from_state_req) {
>> -		ret = -EINVAL;
>> -		goto out;
>> +	list_for_each(pos, &mem->sections) {
>> +		mbs = list_entry(pos, struct memory_block_section, next);
>> +
> 
> list_for_each_entry() ?

That could be done here.

> 
>> +		if (mbs->state != from_state_req)
>> +			continue;
>> +
>> +		ret = memory_block_action(mbs, to_state);
>> +		if (ret)
>> +			break;
>> +	}
> 
> Then, all actions will be affect all memory sections under memory block ?
> (Hmm..maybe have to see following patches ?)

Correct.  Add/remove actions will work on a memory_block as a whole.

> 
> 
>> +
>> +	if (ret) {
>> +		list_for_each(pos, &mem->sections) {
>> +			mbs = list_entry(pos, struct memory_block_section,
>> +					 next);
>> +
> list_for_each_entry() ?

got it. :)

> 
>> +			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);
>> +		}
>>  	}
>>  
>> -	ret = memory_block_action(mem, to_state);
>>  	if (!ret)
>>  		mem->state = to_state;
>>  
>> -out:
>>  	mutex_unlock(&mem->state_mutex);
>>  	return ret;
>>  }
>> @@ -260,20 +295,15 @@
>>  		struct sysdev_attribute *attr, const char *buf, size_t count)
>>  {
> 
> Hmm, store_mem_state() ? What diff option are you using ?

Yes, this is store_mem_state.

Patches were generated with quilt.

> 
> 
>>  	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;
>>  
>>  	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 +465,6 @@
>>  	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;
>> -}
>> -
> 
> 
> please divide clean-up and logic-change patches into their own..

ok.
> 
> 
>>  /*
>>   * For now, we have a linear search to go find the appropriate
>>   * memory_block corresponding to a particular phys_index. If
>> @@ -482,12 +479,13 @@
>>  	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);
> 
> Hmm. Then, the user has to calculate block-id in addtion to section-id.
> Can't we use memory block name as memory%d-%d(start-end) ?

I am not attached to a particular name for the directories.  I think
keeping the memory%d, where %d is the starting id makes the code that splits
the directory cleaner.

In a later patch I add a new file for each directory that has the ending
id in it so users can easily determine the start and end id's of the
memory block.

> 
> 
> 
>>  
>>  	kobj = kset_find_obj(&memory_sysdev_class.kset, name);
>>  	if (!kobj)
>> @@ -498,19 +496,97 @@
>>  
>>  	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;
>> +}
>> +
>> +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);
> 
> I guess you need to add changes to find_memory_block. section-ID != block-ID.

That is above, see the line

>> +	int block_id = base_memory_block_id(__section_nr(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);
> 
> I'm not sure this phys_device is properly set in any arch...but this changes in
> granule will not affect ?

I don't think so, hopefully someone will speak up if this causes an issue.

> 
>> +
>> +		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);
>> +	}
>> +
>> +	if (!ret)
>> +		ret = add_mem_block_section(mem, __section_nr(section), state);
>> +
>> +	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;
>> +	struct list_head *pos, *tmp;
>> +	int section_nr = __section_nr(section);
>>  
>>  	mem = find_memory_block(section);
> 
> ditto.
> 
>> -	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_safe(pos, tmp, &mem->sections) {
>> +		mbs = list_entry(pos, struct memory_block_section, next);
>> +
> list_for_each_entry_safe ?

yep. :)

> 
>> +		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 +608,24 @@
>>  	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 +634,16 @@
>>  	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	2010-07-08 11:27:21.000000000 -0500
>> +++ linux-2.6/include/linux/memory.h	2010-07-09 14:22:44.000000000 -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 };
>> --
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