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Date: Mon, 20 May 2013 11:27:56 -0600
From: Toshi Kani <toshi.kani@...com>
To: "Rafael J. Wysocki" <rjw@...k.pl>
Cc: ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Wen Congyang <wency@...fujitsu.com>,
Tang Chen <tangchen@...fujitsu.com>,
Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jiang Liu <liuj97@...il.com>,
Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>,
linux-mm@...ck.org
Subject: Re: [PATCH 5/5] ACPI / memhotplug: Drop unnecessary code
On Sun, 2013-05-19 at 01:34 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Now that the memory offlining should be taken care of by the
> companion device offlining code in acpi_scan_hot_remove(), the
> ACPI memory hotplug driver doesn't need to offline it in
> acpi_memory_remove_memory() any more. Consequently, it doesn't
> need to call remove_memory() any more, which means that that
> funtion may be dropped entirely, because acpi_memory_remove_memory()
> is the only user of it.
The off-lining part of remove_memory() can be removed, but not the
hot-delete part. Please see my comments below.
> Make the changes described above to get rid of the dead code.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/acpi/acpi_memhotplug.c | 15 ------
> include/linux/memory_hotplug.h | 1
> mm/memory_hotplug.c | 102 -----------------------------------------
> 3 files changed, 2 insertions(+), 116 deletions(-)
>
> Index: linux-pm/drivers/acpi/acpi_memhotplug.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpi_memhotplug.c
> +++ linux-pm/drivers/acpi/acpi_memhotplug.c
> @@ -271,31 +271,20 @@ static int acpi_memory_enable_device(str
> return 0;
> }
>
> -static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
> +static void acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
> {
> acpi_handle handle = mem_device->device->handle;
> - int result = 0, nid;
> struct acpi_memory_info *info, *n;
>
> - nid = acpi_get_node(handle);
> -
> list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
> if (!info->enabled)
> continue;
>
> - if (nid < 0)
> - nid = memory_add_physaddr_to_nid(info->start_addr);
> -
> + /* All of the memory blocks are offline at this point. */
> acpi_unbind_memory_blocks(info, handle);
> - result = remove_memory(nid, info->start_addr, info->length);
We still need to call remove_memory().
> - if (result)
> - return result;
> -
> list_del(&info->list);
> kfree(info);
> }
> -
> - return result;
> }
>
> static void acpi_memory_device_free(struct acpi_memory_device *mem_device)
> Index: linux-pm/include/linux/memory_hotplug.h
> ===================================================================
> --- linux-pm.orig/include/linux/memory_hotplug.h
> +++ linux-pm/include/linux/memory_hotplug.h
> @@ -252,7 +252,6 @@ extern int add_memory(int nid, u64 start
> extern int arch_add_memory(int nid, u64 start, u64 size);
> extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> extern bool is_memblock_offlined(struct memory_block *mem);
> -extern int remove_memory(int nid, u64 start, u64 size);
> extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
> int nr_pages);
> extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);
> Index: linux-pm/mm/memory_hotplug.c
> ===================================================================
> --- linux-pm.orig/mm/memory_hotplug.c
> +++ linux-pm/mm/memory_hotplug.c
> @@ -1670,41 +1670,6 @@ int walk_memory_range(unsigned long star
> }
:
> -
> -int __ref remove_memory(int nid, u64 start, u64 size)
> -{
> - unsigned long start_pfn, end_pfn;
> - int ret = 0;
> - int retry = 1;
> -
> - start_pfn = PFN_DOWN(start);
> - end_pfn = PFN_UP(start + size - 1);
> -
> - /*
> - * When CONFIG_MEMCG is on, one memory block may be used by other
> - * blocks to store page cgroup when onlining pages. But we don't know
> - * in what order pages are onlined. So we iterate twice to offline
> - * memory:
> - * 1st iterate: offline every non primary memory block.
> - * 2nd iterate: offline primary (i.e. first added) memory block.
> - */
> -repeat:
> - walk_memory_range(start_pfn, end_pfn, &ret,
> - offline_memory_block_cb);
> - if (ret) {
> - if (!retry)
> - return ret;
> -
> - retry = 0;
> - ret = 0;
> - goto repeat;
> - }
The above procedure can be removed as it is for off-lining.
> - lock_memory_hotplug();
> -
> - /*
> - * we have offlined all memory blocks like this:
> - * 1. lock memory hotplug
> - * 2. offline a memory block
> - * 3. unlock memory hotplug
> - *
> - * repeat step1-3 to offline the memory block. All memory blocks
> - * must be offlined before removing memory. But we don't hold the
> - * lock in the whole operation. So we should check whether all
> - * memory blocks are offlined.
> - */
> -
> - ret = walk_memory_range(start_pfn, end_pfn, NULL,
> - is_memblock_offlined_cb);
> - if (ret) {
> - unlock_memory_hotplug();
> - return ret;
> - }
> -
I think the above procedure is still useful for safe guard.
> - /* remove memmap entry */
> - firmware_map_remove(start, start + size, "System RAM");
> -
> - arch_remove_memory(start, size);
> -
> - try_offline_node(nid);
The above procedure performs memory hot-delete specific operations and
is necessary.
Thanks,
-Toshi
> - unlock_memory_hotplug();
> -
> - return 0;
> -}
--
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