On 05/24/2017 03:42 PM, Michal Hocko wrote:
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index ec7d6ae01c96..64aed7386fe4 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2246,11 +2246,11 @@
> that the amount of memory usable for all allocations
> is not too small.
>
> - movable_node [KNL] Boot-time switch to make hotplugable to be
> - movable. This means that the memory of such nodes
> - will be usable only for movable allocations which
> - rules out almost all kernel allocations. Use with
> - caution!
> + movable_node [KNL] Boot-time switch to make hotplugable memory
> + NUMA nodes to be movable. This means that the memory
> + of such nodes will be usable only for movable
> + allocations which rules out almost all kernel
> + allocations. Use with caution!
>
> MTD_Partition= [MTD]
> Format: <name>,<region-number>,<size>,<offset>
>
> Better?
Yes, thanks.
> [...]
>>> --- a/mm/Kconfig
>>> +++ b/mm/Kconfig
>>> @@ -149,32 +149,6 @@ config NO_BOOTMEM
>>> config MEMORY_ISOLATION
>>> bool
>>>
>>> -config MOVABLE_NODE
>>> - bool "Enable to assign a node which has only movable memory"
>>> - depends on HAVE_MEMBLOCK
>>> - depends on NO_BOOTMEM
>>> - depends on X86_64 || OF_EARLY_FLATTREE || MEMORY_HOTPLUG
>>> - depends on NUMA
>>
>> That's a lot of depends. What happens if some of them are not met and
>> the movable_node bootparam is used?
>
> Good question. I haven't explored that, to be honest. Now that I am looking closer
> I am not even sure why all those dependencies are thre. MEMORY_HOTPLUG
> is clear and OF_EARLY_FLATTREE is explained by 41a9ada3e6b4 ("of/fdt:
> mark hotpluggable memory"). NUMA is less clear to me because
> MEMORY_HOTPLUG doesn't really depend on NUMA systems. Dependency on
> NO_BOOTMEM is also not clear to me because zones layout
> doesn't really depend on the specific boot time allocator.
>
> So we are left with HAVE_MEMBLOCK which seems to be there because
> movable_node_enabled is defined there while the parameter handling is in
> the hotplug proper. But there is no real reason to have it like that.
> This compiles but I will have to put throw my full compile battery on it
> to be sure. I will make it a separate patch.
I'd expect stuff might compile and work (run without crash), just in
some cases the boot option could be effectively ignored? In that case
it's just a matter of documenting the option, possibly also some warning
when used, e.g. "node_movable was ignored because CONFIG_FOO is not
enabled"?
Vlastimil
> Thanks!
> ---
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 9622fb8c101b..071692894254 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -57,8 +57,6 @@ struct memblock {
>
> extern struct memblock memblock;
> extern int memblock_debug;
> -/* If movable_node boot option specified */
> -extern bool movable_node_enabled;
>
> #ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
> #define __init_memblock __meminit
> @@ -171,11 +169,6 @@ static inline bool memblock_is_hotpluggable(struct memblock_region *m)
> return m->flags & MEMBLOCK_HOTPLUG;
> }
>
> -static inline bool __init_memblock movable_node_is_enabled(void)
> -{
> - return movable_node_enabled;
> -}
> -
> static inline bool memblock_is_mirror(struct memblock_region *m)
> {
> return m->flags & MEMBLOCK_MIRROR;
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 9e0249d0f5e4..9c1ac94f857b 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -115,6 +115,12 @@ extern void __online_page_free(struct page *page);
> extern int try_online_node(int nid);
>
> extern bool memhp_auto_online;
> +/* If movable_node boot option specified */
> +extern bool movable_node_enabled;
> +static inline bool movable_node_is_enabled(void)
> +{
> + return movable_node_enabled;
> +}
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> extern bool is_pageblock_removable_nolock(struct page *page);
> @@ -266,6 +272,10 @@ static inline void put_online_mems(void) {}
> static inline void mem_hotplug_begin(void) {}
> static inline void mem_hotplug_done(void) {}
>
> +static inline bool __init_memblock movable_node_is_enabled(void)
> +{
> + return false;
> +}
> #endif /* ! CONFIG_MEMORY_HOTPLUG */
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4895f5a6cf7e..8c52fb11510c 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -54,7 +54,6 @@ struct memblock memblock __initdata_memblock = {
> };
>
> int memblock_debug __initdata_memblock;
> -bool movable_node_enabled __initdata_memblock = false;
> static bool system_has_some_mirror __initdata_memblock = false;
> static int memblock_can_resize __initdata_memblock;
> static int memblock_memory_in_slab __initdata_memblock = 0;
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 2a14f8c18a22..b0d2bf3256d0 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -79,6 +79,8 @@ static struct {
> #define memhp_lock_acquire() lock_map_acquire(&mem_hotplug.dep_map)
> #define memhp_lock_release() lock_map_release(&mem_hotplug.dep_map)
>
> +bool movable_node_enabled = false;
> +
> #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE
> bool memhp_auto_online;
> #else
>
--
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