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SubjectRe: [PATCH 4/7] Allow sysfs memory directories to be split
On 07/13/2010 01:28 AM, KAMEZAWA Hiroyuki wrote:
> On Mon, 12 Jul 2010 10:45:25 -0500
> Nathan Fontenot <nfont@austin.ibm.com> wrote:
>
>> This patch introduces the new 'split' file in each memory sysfs
>> directory and the associated routines needed to handle splitting
>> a directory.
>>
>> Signed-off-by; Nathan Fontenot <nfont@austin.ibm.com>
>> ---
>
> pleae check diff option...
>
>
>> drivers/base/memory.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 98 insertions(+), 1 deletion(-)
>>
>> Index: linux-2.6/drivers/base/memory.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/base/memory.c 2010-07-09 14:23:20.000000000 -0500
>> +++ linux-2.6/drivers/base/memory.c 2010-07-09 14:38:09.000000000 -0500
>> @@ -32,6 +32,9 @@
>>
>> static int sections_per_block;
>>
>> +static int register_memory(struct memory_block *, struct mem_section *,
>> + int, enum mem_add_context);
>> +
>> static inline int base_memory_block_id(int section_nr)
>> {
>> return (section_nr / sections_per_block) * sections_per_block;
>> @@ -309,11 +312,100 @@
>> return sprintf(buf, "%d\n", mem->phys_device);
>> }
>>
>> +static void update_memory_block_phys_indexes(struct memory_block *mem)
>> +{
>> + struct list_head *pos;
>> + struct memory_block_section *mbs;
>> + unsigned long min_index = 0xffffffff;
>> + unsigned long max_index = 0;
>> +
>> + list_for_each(pos, &mem->sections) {
>> + mbs = list_entry(pos, struct memory_block_section, next);
>> +
>> + if (mbs->phys_index < min_index)
>> + min_index = mbs->phys_index;
>> +
>> + if (mbs->phys_index > max_index)
>> + max_index = mbs->phys_index;
>> + }
>> +
>> + mem->start_phys_index = min_index;
>> + mem->end_phys_index = max_index;
>> +}
>> +
>> +static ssize_t
>> +store_mem_split_block(struct sys_device *dev, struct sysdev_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + struct memory_block *mem, *new_mem_blk;
>> + struct memory_block_section *mbs;
>> + struct list_head *pos, *tmp;
>> + struct mem_section *section;
>> + int min_scn_nr = 0;
>> + int max_scn_nr = 0;
>> + int total_scns = 0;
>> + int new_blk_min, new_blk_total;
>> + int ret = -EINVAL;
>> +
>> + mem = container_of(dev, struct memory_block, sysdev);
>> +
>> + if (list_is_singular(&mem->sections))
>> + return -EINVAL;
>
> What this means ?

list_is_singular() will return true if there is only one item
on the list. In this case we cannot split a memory_block with
only one memory_block_section.

>
>
>> +
>> + mutex_lock(&mem->state_mutex);
>> +
>> + list_for_each(pos, &mem->sections) {
>> + mbs = list_entry(pos, struct memory_block_section, next);
>> +
>> + total_scns++;
>> +
>> + if (min_scn_nr > mbs->phys_index)
>> + min_scn_nr = mbs->phys_index;
>> +
>> + if (max_scn_nr < mbs->phys_index)
>> + max_scn_nr = mbs->phys_index;
>> + }
>> +
>> + new_mem_blk = kzalloc(sizeof(*new_mem_blk), GFP_KERNEL);
>> + if (!new_mem_blk)
>> + return -ENOMEM;
>> +
>> + mutex_init(&new_mem_blk->state_mutex);
>> + INIT_LIST_HEAD(&new_mem_blk->sections);
>> + new_mem_blk->state = mem->state;
>> +
>> + mutex_lock(&new_mem_blk->state_mutex);
>> +
>> + new_blk_total = total_scns / 2;
>> + new_blk_min = max_scn_nr - new_blk_total + 1;
>> +
>> + section = __nr_to_section(new_blk_min);
>> + ret = register_memory(new_mem_blk, section, 0, HOTPLUG);
>> +
> 'nid' is always 0 ?

Ahh.. good catch. it may not be. I'll look into finding the correct nid.

>
> And for what purpose this interface is ? Does this split memory block into 2 pieces
> of the same size ?? sounds __very__ strange interface to me.

Yes, this splits the memory_block into two blocks of the same size. This was
suggested as something we may want to do. From ppc perspective I am not sure we
would use this.

The split functionality is not required. The main goal of the patch set is to
reduce the number of memory sysfs directories created. From a ppc perspective
the split functionality is not really needed.

>
> If this is necessary, I hope move the whole things to configfs rather than
> something tricky.
>
> Bye.
> -Kame
>



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