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SubjectRe: [PATCH v3 1/5] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY
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On 25.07.19 18:02, Oscar Salvador wrote:
> This patch introduces MHP_MEMMAP_ON_MEMORY flag,
> and prepares the callers that add memory to take a "flags" parameter.
> This "flags" parameter will be evaluated later on in Patch#3
> to init mhp_restrictions struct.
>
> The callers are:
>
> add_memory
> __add_memory
> add_memory_resource
>
> Unfortunately, we do not have a single entry point to add memory, as depending
> on the requisites of the caller, they want to hook up in different places,
> (e.g: Xen reserve_additional_memory()), so we have to spread the parameter
> in the three callers.
>
> MHP_MEMMAP_ON_MEMORY flag parameter will specify to allocate memmaps
> from the hot-added range.
> If callers wants memmaps to be allocated per memory block, it will
> have to call add_memory() variants in memory-block granularity
> spanning the whole range, while if it wants to allocate memmaps
> per whole memory range, just one call will do.
>
> Want to add 384MB (3 sections, 3 memory-blocks)
> e.g:
>
> add_memory(0x1000, size_memory_block);
> add_memory(0x2000, size_memory_block);
> add_memory(0x3000, size_memory_block);
>
> [memblock#0 ]
> [0 - 511 pfns ] - vmemmaps for section#0
> [512 - 32767 pfns ] - normal memory
>
> [memblock#1 ]
> [32768 - 33279 pfns] - vmemmaps for section#1
> [33280 - 65535 pfns] - normal memory
>
> [memblock#2 ]
> [65536 - 66047 pfns] - vmemmap for section#2
> [66048 - 98304 pfns] - normal memory

I wouldn't even care about documenting this right now. We have no user
so far, so spending 50% of the description on this topic isn't really
needed IMHO :)

>
> or
> add_memory(0x1000, size_memory_block * 3);
>
> [memblock #0 ]
> [0 - 1533 pfns ] - vmemmap for section#{0-2}
> [1534 - 98304 pfns] - normal memory
>
> When using larger memory blocks (1GB or 2GB), the principle is the same.
>
> Of course, per whole-range granularity is nicer when it comes to have a large
> contigous area, while per memory-block granularity allows us to have flexibility
> when removing the memory.

E.g., in my virtio-mem I am currently adding all memory blocks
separately either way (to guranatee that remove_memory() works cleanly -
see __release_memory_resource()), and to control the amount of
not-offlined memory blocks (e.g., to make user space is actually
onlining them). As it's just a prototype, this might change of course in
the future.

>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
> drivers/acpi/acpi_memhotplug.c | 2 +-
> drivers/base/memory.c | 2 +-
> drivers/dax/kmem.c | 2 +-
> drivers/hv/hv_balloon.c | 2 +-
> drivers/s390/char/sclp_cmd.c | 2 +-
> drivers/xen/balloon.c | 2 +-
> include/linux/memory_hotplug.h | 25 ++++++++++++++++++++++---
> mm/memory_hotplug.c | 10 +++++-----
> 8 files changed, 33 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> index e294f44a7850..d91b3584d4b2 100644
> --- a/drivers/acpi/acpi_memhotplug.c
> +++ b/drivers/acpi/acpi_memhotplug.c
> @@ -207,7 +207,7 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
> if (node < 0)
> node = memory_add_physaddr_to_nid(info->start_addr);
>
> - result = __add_memory(node, info->start_addr, info->length);
> + result = __add_memory(node, info->start_addr, info->length, 0);
>
> /*
> * If the memory block has been used by the kernel, add_memory()
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 154d5d4a0779..d30d0f6c8ad0 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -521,7 +521,7 @@ static ssize_t probe_store(struct device *dev, struct device_attribute *attr,
>
> nid = memory_add_physaddr_to_nid(phys_addr);
> ret = __add_memory(nid, phys_addr,
> - MIN_MEMORY_BLOCK_SIZE * sections_per_block);
> + MIN_MEMORY_BLOCK_SIZE * sections_per_block, 0);
>
> if (ret)
> goto out;
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 3d0a7e702c94..e159184e0ba0 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -65,7 +65,7 @@ int dev_dax_kmem_probe(struct device *dev)
> new_res->flags = IORESOURCE_SYSTEM_RAM;
> new_res->name = dev_name(dev);
>
> - rc = add_memory(numa_node, new_res->start, resource_size(new_res));
> + rc = add_memory(numa_node, new_res->start, resource_size(new_res), 0);
> if (rc) {
> release_resource(new_res);
> kfree(new_res);
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index 6fb4ea5f0304..beb92bc56186 100644
> --- a/drivers/hv/hv_balloon.c
> +++ b/drivers/hv/hv_balloon.c
> @@ -731,7 +731,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
>
> nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
> ret = add_memory(nid, PFN_PHYS((start_pfn)),
> - (HA_CHUNK << PAGE_SHIFT));
> + (HA_CHUNK << PAGE_SHIFT), 0);
>
> if (ret) {
> pr_err("hot_add memory failed error is %d\n", ret);
> diff --git a/drivers/s390/char/sclp_cmd.c b/drivers/s390/char/sclp_cmd.c
> index 37d42de06079..f61026c7db7e 100644
> --- a/drivers/s390/char/sclp_cmd.c
> +++ b/drivers/s390/char/sclp_cmd.c
> @@ -406,7 +406,7 @@ static void __init add_memory_merged(u16 rn)
> if (!size)
> goto skip_add;
> for (addr = start; addr < start + size; addr += block_size)
> - add_memory(numa_pfn_to_nid(PFN_DOWN(addr)), addr, block_size);
> + add_memory(numa_pfn_to_nid(PFN_DOWN(addr)), addr, block_size, 0);
> skip_add:
> first_rn = rn;
> num = 1;
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 4e11de6cde81..e4934ce40478 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -349,7 +349,7 @@ static enum bp_state reserve_additional_memory(void)
> mutex_unlock(&balloon_mutex);
> /* add_memory_resource() requires the device_hotplug lock */
> lock_device_hotplug();
> - rc = add_memory_resource(nid, resource);
> + rc = add_memory_resource(nid, resource, 0);
> unlock_device_hotplug();
> mutex_lock(&balloon_mutex);
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index f46ea71b4ffd..45dece922d7c 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -54,6 +54,25 @@ enum {
> };
>
> /*
> + * We want memmap (struct page array) to be allocated from the hotadded range.
> + * To do so, there are two possible ways depending on what the caller wants.
> + * 1) Allocate memmap pages whole hot-added range.
> + * Here the caller will only call any add_memory() variant with the whole
> + * memory address.
> + * 2) Allocate memmap pages per memblock
> + * Here, the caller will call any add_memory() variant per memblock
> + * granularity.
> + * The former implies that we will use the beginning of the hot-added range
> + * to store the memmap pages of the whole range, while the latter implies
> + * that we will use the beginning of each memblock to store its own memmap
> + * pages.

Can you make this documentation only state how MHP_MEMMAP_ON_MEMORY
works? (IOW, shrink it heavily to what we actually implement)

> + *
> + * Please note that this is only a hint, not a guarantee. Only selected
> + * architectures support it with SPARSE_VMEMMAP.
> + */
> +#define MHP_MEMMAP_ON_MEMORY (1UL<<1)
> +
> +/*
> * Restrictions for the memory hotplug:
> * flags: MHP_ flags
> * altmap: alternative allocator for memmap array
> @@ -340,9 +359,9 @@ static inline void __remove_memory(int nid, u64 start, u64 size) {}
> #endif /* CONFIG_MEMORY_HOTREMOVE */
>
> extern void __ref free_area_init_core_hotplug(int nid);
> -extern int __add_memory(int nid, u64 start, u64 size);
> -extern int add_memory(int nid, u64 start, u64 size);
> -extern int add_memory_resource(int nid, struct resource *resource);
> +extern int __add_memory(int nid, u64 start, u64 size, unsigned long flags);
> +extern int add_memory(int nid, u64 start, u64 size, unsigned long flags);
> +extern int add_memory_resource(int nid, struct resource *resource, unsigned long flags);
> extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
> unsigned long nr_pages, struct vmem_altmap *altmap);
> extern bool is_memblock_offlined(struct memory_block *mem);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 9a82e12bd0e7..3d97c3711333 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1046,7 +1046,7 @@ static int online_memory_block(struct memory_block *mem, void *arg)
> *
> * we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG
> */
> -int __ref add_memory_resource(int nid, struct resource *res)
> +int __ref add_memory_resource(int nid, struct resource *res, unsigned long flags)
> {
> struct mhp_restrictions restrictions = {};
> u64 start, size;
> @@ -1123,7 +1123,7 @@ int __ref add_memory_resource(int nid, struct resource *res)
> }
>
> /* requires device_hotplug_lock, see add_memory_resource() */
> -int __ref __add_memory(int nid, u64 start, u64 size)
> +int __ref __add_memory(int nid, u64 start, u64 size, unsigned long flags)
> {
> struct resource *res;
> int ret;
> @@ -1132,18 +1132,18 @@ int __ref __add_memory(int nid, u64 start, u64 size)
> if (IS_ERR(res))
> return PTR_ERR(res);
>
> - ret = add_memory_resource(nid, res);
> + ret = add_memory_resource(nid, res, flags);
> if (ret < 0)
> release_memory_resource(res);
> return ret;
> }
>
> -int add_memory(int nid, u64 start, u64 size)
> +int add_memory(int nid, u64 start, u64 size, unsigned long flags)
> {
> int rc;
>
> lock_device_hotplug();
> - rc = __add_memory(nid, start, size);
> + rc = __add_memory(nid, start, size, flags);
> unlock_device_hotplug();
>
> return rc;
>

Apart from the requested description/documentation changes

Reviewed-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David / dhildenb

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