From: Wen Congyang <wency@cn.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
linux-ia64@vger.kernel.org, cmetcalf@tilera.com,
sparclinux@vger.kernel.org, rientjes@google.com,
liuj97@gmail.com, len.brown@intel.com, benh@kernel.crashing.org,
paulus@samba.org, cl@linux.com, minchan.kim@gmail.com,
kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com
Subject: Re: [RFC v8 PATCH 08/20] memory-hotplug: remove /sys/firmware/memmap/X sysfs
Date: Mon, 03 Sep 2012 15:31:00 +0800 [thread overview]
Message-ID: <50445CB4.80303@cn.fujitsu.com> (raw)
In-Reply-To: <20120831140623.8d13bd2c.akpm@linux-foundation.org>
At 09/01/2012 05:06 AM, Andrew Morton Wrote:
> On Tue, 28 Aug 2012 18:00:15 +0800
> wency@cn.fujitsu.com wrote:
>
>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> When (hot)adding memory into system, /sys/firmware/memmap/X/{end, start, type}
>> sysfs files are created. But there is no code to remove these files. The patch
>> implements the function to remove them.
>>
>> Note : The code does not free firmware_map_entry since there is no way to free
>> memory which is allocated by bootmem.
>>
>> ....
>>
>> +#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
>
> It would be better to implement this as an inlined C function. That
> has improved type safety and improved readability.
Hmm, this macro is not a new macro. It is defined after the function
release_firmware_map_entry(). We just moved it here because we
need it in the function release_firmware_map_entry().
>
>> +static void release_firmware_map_entry(struct kobject *kobj)
>> +{
>> + struct firmware_map_entry *entry = to_memmap_entry(kobj);
>> + struct page *page;
>> +
>> + page = virt_to_page(entry);
>> + if (PageSlab(page) || PageCompound(page))
>
> That PageCompound() test looks rather odd. Why is this done?
>
>> + kfree(entry);
>> +
>> + /* There is no way to free memory allocated from bootmem*/
>> +}
>
> This function is a bit ugly - poking around in page flags to determine
> whether or not the memory came from bootmem. It would be cleaner to
> use a separate boolean. Although I guess we can live with it as you
> have it here.
>
>> static struct kobj_type memmap_ktype = {
>> + .release = release_firmware_map_entry,
>> .sysfs_ops = &memmap_attr_ops,
>> .default_attrs = def_attrs,
>> };
>> @@ -123,6 +139,16 @@ static int firmware_map_add_entry(u64 start, u64 end,
>> return 0;
>> }
>>
>> +/**
>> + * firmware_map_remove_entry() - Does the real work to remove a firmware
>> + * memmap entry.
>> + * @entry: removed entry.
>> + **/
>> +static inline void firmware_map_remove_entry(struct firmware_map_entry *entry)
>> +{
>> + list_del(&entry->list);
>> +}
>
> Is there no locking to protect that list?
OK, I will add a lock to protect it.
Thanks
Wen Congyang
>
>> /*
>> * Add memmap entry on sysfs
>> */
>> @@ -144,6 +170,31 @@ static int add_sysfs_fw_map_entry(struct firmware_map_entry *entry)
>> return 0;
>> }
>>
>> +/*
>> + * Remove memmap entry on sysfs
>> + */
>> +static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
>> +{
>> + kobject_put(&entry->kobj);
>> +}
>> +
>> +/*
>> + * Search memmap entry
>> + */
>> +
>> +struct firmware_map_entry * __meminit
>> +find_firmware_map_entry(u64 start, u64 end, const char *type)
>
> A better name would be firmware_map_find_entry(). To retain the (good)
> convention that symbols exported from here all start with
> "firmware_map_".
>
>> +{
>> + struct firmware_map_entry *entry;
>> +
>> + list_for_each_entry(entry, &map_entries, list)
>> + if ((entry->start == start) && (entry->end == end) &&
>> + (!strcmp(entry->type, type)))
>> + return entry;
>> +
>> + return NULL;
>> +}
>> +
>> /**
>> * firmware_map_add_hotplug() - Adds a firmware mapping entry when we do
>> * memory hotplug.
>> @@ -196,6 +247,32 @@ int __init firmware_map_add_early(u64 start, u64 end, const char *type)
>> return firmware_map_add_entry(start, end, type, entry);
>> }
>>
>> +/**
>> + * firmware_map_remove() - remove a firmware mapping entry
>> + * @start: Start of the memory range.
>> + * @end: End of the memory range.
>> + * @type: Type of the memory range.
>> + *
>> + * removes a firmware mapping entry.
>> + *
>> + * Returns 0 on success, or -EINVAL if no entry.
>> + **/
>> +int __meminit firmware_map_remove(u64 start, u64 end, const char *type)
>> +{
>> + struct firmware_map_entry *entry;
>> +
>> + entry = find_firmware_map_entry(start, end - 1, type);
>> + if (!entry)
>> + return -EINVAL;
>> +
>> + firmware_map_remove_entry(entry);
>> +
>> + /* remove the memmap entry */
>> + remove_sysfs_fw_map_entry(entry);
>> +
>> + return 0;
>> +}
>
> Again, the lack of locking looks bad.
>
>> ...
>>
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1052,9 +1052,9 @@ int offline_memory(u64 start, u64 size)
>> return 0;
>> }
>>
>> -int remove_memory(int nid, u64 start, u64 size)
>> +int __ref remove_memory(int nid, u64 start, u64 size)
>
> Why was __ref added?
>
>> {
>> - int ret = -EBUSY;
>> + int ret = 0;
>> lock_memory_hotplug();
>> /*
>> * The memory might become online by other task, even if you offine it.
>>
>> ...
>>
>
next prev parent reply other threads:[~2012-09-03 7:44 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-28 10:00 [RFC v8 PATCH 00/20] memory-hotplug: hot-remove physical memory wency
2012-08-28 10:00 ` [RFC v8 PATCH 01/20] memory-hotplug: rename remove_memory() to offline_memory()/offline_pages() wency
2012-08-28 10:00 ` [RFC v8 PATCH 02/20] memory-hotplug: implement offline_memory() wency
2012-08-28 10:00 ` [RFC v8 PATCH 03/20] memory-hotplug: store the node id in acpi_memory_device wency
2012-08-28 10:00 ` [RFC v8 PATCH 04/20] memory-hotplug: offline and remove memory when removing the memory device wency
2012-08-31 20:55 ` Andrew Morton
2012-09-03 1:30 ` Wen Congyang
2012-08-28 10:00 ` [RFC v8 PATCH 05/20] memory-hotplug: check whether memory is present or not wency
2012-08-28 10:00 ` [RFC v8 PATCH 06/20] memory-hotplug: export the function acpi_bus_remove() wency
2012-08-28 10:00 ` [RFC v8 PATCH 07/20] memory-hotplug: call acpi_bus_remove() to remove memory device wency
2012-08-28 10:00 ` [RFC v8 PATCH 08/20] memory-hotplug: remove /sys/firmware/memmap/X sysfs wency
2012-08-31 21:06 ` Andrew Morton
2012-09-03 5:51 ` Wen Congyang
2012-09-04 23:16 ` Andrew Morton
2012-09-05 1:41 ` Wen Congyang
2012-09-03 7:31 ` Wen Congyang [this message]
2012-08-28 10:00 ` [RFC v8 PATCH 09/20] memory-hotplug: does not release memory region in PAGES_PER_SECTION chunks wency
2012-08-28 10:00 ` [RFC v8 PATCH 10/20] memory-hotplug: add memory_block_release wency
2012-08-28 10:00 ` [RFC v8 PATCH 11/20] memory-hotplug: remove_memory calls __remove_pages wency
2012-08-28 10:00 ` [RFC v8 PATCH 12/20] memory-hotplug: introduce new function arch_remove_memory() wency
2012-08-28 10:00 ` [RFC v8 PATCH 13/20] memory-hotplug: check page type in get_page_bootmem wency
2012-08-31 21:30 ` Andrew Morton
2012-09-04 3:46 ` Wen Congyang
2012-09-04 9:54 ` Yasuaki Ishimatsu
2012-08-28 10:00 ` [RFC v8 PATCH 14/20] memory-hotplug: move register_page_bootmem_info_node and put_page_bootmem for sparse-vmemmap wency
2012-08-28 10:00 ` [RFC v8 PATCH 15/20] memory-hotplug: implement register_page_bootmem_info_section of sparse-vmemmap wency
2012-08-28 10:00 ` [RFC v8 PATCH 16/20] memory-hotplug: free memmap " wency
2012-08-28 10:00 ` [RFC v8 PATCH 17/20] memory_hotplug: clear zone when the memory is removed wency
2012-08-28 10:00 ` [RFC v8 PATCH 18/20] memory-hotplug: add node_device_release wency
2012-08-28 10:00 ` [RFC v8 PATCH 19/20] memory-hotplug: remove sysfs file of node wency
2012-08-28 10:00 ` [RFC v8 PATCH 20/20] memory-hotplug: clear hwpoisoned flag when onlining pages wency
2012-08-31 20:49 ` [RFC v8 PATCH 00/20] memory-hotplug: hot-remove physical memory Andrew Morton
2012-09-10 1:46 ` Yasuaki Ishimatsu
2012-09-10 2:01 ` Wen Congyang
2012-09-10 13:52 ` Vasilis Liaskovitis
[not found] ` <CAAV+Mu7YWRWnxt78F4ZDMrrUsWB=n-_qkYOcQT7WQ2HwP89Obw@mail.gmail.com>
2012-09-11 1:23 ` Minchan Kim
[not found] ` <CAAV+Mu4hb0qbW2Ry6w5FAGUM06puDH0v_H-jr584-G9CzJqSGw@mail.gmail.com>
2012-09-11 5:39 ` Wen Congyang
2012-09-12 6:17 ` Minchan Kim
2012-09-11 1:25 ` Wen Congyang
2012-09-12 5:20 ` Wen Congyang
2012-09-12 17:18 ` Vasilis Liaskovitis
2012-09-18 9:39 ` Wen Congyang
2012-09-19 17:02 ` Vasilis Liaskovitis
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