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SubjectRe: [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 <nfont@austin.ibm.com> wrote:
>
>> 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 <nfont@austin.ibm.com>
>> ---
>> 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.

>
>
>> return sprintf(buf, "%d\n", ret);
>> }
>>
>> @@ -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;
>> + int old_state = mbs->state;
>>
>> - 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 +252,34 @@
>
> And please check quilt's diff option.
> Usual patche in ML shows a function name in any changes, as
> @@ -241,6 +293,8 @@ static int memory_block_change_state(str
>
> Maybe "-p" option is lacked..

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

>
>
>> 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.

>
>> + }
>> }
>>
>> - 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.

>
>
>
>> 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.

>
>
>> /*
>> * 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.

>
>
>> +
>> +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
>
>
>
>



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