On Tue, 28 Aug 2012 18:00:15 +0800
wency@xxxxxxxxxxxxxx wrote:
> From: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
>
> 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.
> +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?
> /*
> * 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.
>
> ...
>
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