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SubjectRe: [PATCH v5 03/14] memory-hotplug: remove redundant codes
(2012/12/24 21:09), Tang Chen wrote:
> From: Wen Congyang <wency@cn.fujitsu.com>
>
> offlining memory blocks and checking whether memory blocks are offlined
> are very similar. This patch introduces a new function to remove
> redundant codes.
>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
> mm/memory_hotplug.c | 101 ++++++++++++++++++++++++++++-----------------------
> 1 files changed, 55 insertions(+), 46 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index d43d97b..dbb04d8 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1381,20 +1381,14 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
> return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
> }
>
> -int remove_memory(u64 start, u64 size)

please add explanation of this function here. If (*func) returns val other than 0,
this function will fail and returns callback's return value...right ?


> +static int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
> + void *arg, int (*func)(struct memory_block *, void *))
> {
> struct memory_block *mem = NULL;
> struct mem_section *section;
> - unsigned long start_pfn, end_pfn;
> unsigned long pfn, section_nr;
> int ret;
> - int return_on_error = 0;
> - int retry = 0;
> -
> - start_pfn = PFN_DOWN(start);
> - end_pfn = start_pfn + PFN_DOWN(size);
>
> -repeat:

Shouldn't we check lock is held here ? (VM_BUG_ON(!mutex_is_locked(&mem_hotplug_mutex);


> for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> section_nr = pfn_to_section_nr(pfn);
> if (!present_section_nr(section_nr))
> @@ -1411,22 +1405,61 @@ repeat:
> if (!mem)
> continue;
>
> - ret = offline_memory_block(mem);
> + ret = func(mem, arg);
> if (ret) {
> - if (return_on_error) {
> - kobject_put(&mem->dev.kobj);
> - return ret;
> - } else {
> - retry = 1;
> - }
> + kobject_put(&mem->dev.kobj);
> + return ret;
> }
> }
>
> if (mem)
> kobject_put(&mem->dev.kobj);
>
> - if (retry) {
> - return_on_error = 1;
> + return 0;
> +}
> +
> +static int offline_memory_block_cb(struct memory_block *mem, void *arg)
> +{
> + int *ret = arg;
> + int error = offline_memory_block(mem);
> +
> + if (error != 0 && *ret == 0)
> + *ret = error;
> +
> + return 0;

Always returns 0 and run through all mem blocks for scan-and-retry, right ?
You need explanation here !


> +}
> +
> +static int is_memblock_offlined_cb(struct memory_block *mem, void *arg)
> +{
> + int ret = !is_memblock_offlined(mem);
> +
> + if (unlikely(ret))
> + pr_warn("removing memory fails, because memory "
> + "[%#010llx-%#010llx] is onlined\n",
> + PFN_PHYS(section_nr_to_pfn(mem->start_section_nr)),
> + PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1);
> +
> + return ret;
> +}
> +
> +int remove_memory(u64 start, u64 size)
> +{
> + unsigned long start_pfn, end_pfn;
> + int ret = 0;
> + int retry = 1;
> +
> + start_pfn = PFN_DOWN(start);
> + end_pfn = start_pfn + PFN_DOWN(size);
> +
> +repeat:

please explan why you repeat here .

> + walk_memory_range(start_pfn, end_pfn, &ret,
> + offline_memory_block_cb);
> + if (ret) {
> + if (!retry)
> + return ret;
> +
> + retry = 0;
> + ret = 0;
> goto repeat;
> }
>
> @@ -1444,37 +1477,13 @@ repeat:
> * memory blocks are offlined.
> */
>
> - for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> - section_nr = pfn_to_section_nr(pfn);
> - if (!present_section_nr(section_nr))
> - continue;
> -
> - section = __nr_to_section(section_nr);
> - /* same memblock? */
> - if (mem)
> - if ((section_nr >= mem->start_section_nr) &&
> - (section_nr <= mem->end_section_nr))
> - continue;
> -
> - mem = find_memory_block_hinted(section, mem);
> - if (!mem)
> - continue;
> -
> - ret = is_memblock_offlined(mem);
> - if (!ret) {
> - pr_warn("removing memory fails, because memory "
> - "[%#010llx-%#010llx] is onlined\n",
> - PFN_PHYS(section_nr_to_pfn(mem->start_section_nr)),
> - PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1)) - 1);
> -
> - kobject_put(&mem->dev.kobj);
> - unlock_memory_hotplug();
> - return ret;
> - }

please explain what you do here. confirming all memory blocks are offlined
before returning 0 ....right ?

> + ret = walk_memory_range(start_pfn, end_pfn, NULL,
> + is_memblock_offlined_cb);
> + if (ret) {
> + unlock_memory_hotplug();
> + return ret;
> }
>
> - if (mem)
> - kobject_put(&mem->dev.kobj);
> unlock_memory_hotplug();
>
> return 0;
>

Thanks,
-Kame



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