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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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