Re: [HMM 01/16] mm/memory/hotplug: add memory type parameter to arch_add/remove_memory

Michal Hocko
2017-04-07T12:14:05Z

On Wed 05-04-17 16:40:11, Jérôme Glisse wrote:
> When hotpluging memory we want more information on the type of memory.
> This is to extend ZONE_DEVICE to support new type of memory other than
> the persistent memory. Existing user of ZONE_DEVICE (persistent memory)
> will be left un-modified.

My current hotplug rework [1] is touching this path as well. It is not
really clear from the chage why you are changing this and what are the
further expectations of MEMORY_DEVICE_PERSISTENT. Infact I have replaced
for_device with want__memblock [2]. I plan to repost shortly but I would
like to understand your modifications more to reduce potential conflicts
in the code. Why do you need to distinguish different types of memory
anyway.

[1] http://lkml.kernel.org/r/20170330115454.32154-1-mhocko@kernel.org
[2] the current patchset is in git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
branch attempts/rewrite-mem_hotplug-WIP
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: Chris Metcalf <cmetcalf@mellanox.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
> arch/ia64/mm/init.c | 36 +++++++++++++++++++++++++++++++++---
> arch/powerpc/mm/mem.c | 37 ++++++++++++++++++++++++++++++++++---
> arch/s390/mm/init.c | 16 ++++++++++++++--
> arch/sh/mm/init.c | 35 +++++++++++++++++++++++++++++++++--
> arch/x86/mm/init_32.c | 41 +++++++++++++++++++++++++++++++++++++----
> arch/x86/mm/init_64.c | 39 +++++++++++++++++++++++++++++++++++----
> include/linux/memory_hotplug.h | 24 ++++++++++++++++++++++--
> include/linux/memremap.h | 2 ++
> kernel/memremap.c | 5 +++--
> mm/memory_hotplug.c | 4 ++--
> 10 files changed, 215 insertions(+), 24 deletions(-)
>
> diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
> index 06cdaef..c910b3f 100644
> --- a/arch/ia64/mm/init.c
> +++ b/arch/ia64/mm/init.c
> @@ -645,20 +645,36 @@ mem_init (void)
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> pg_data_t *pgdat;
> struct zone *zone;
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + bool for_device = false;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + case MEMORY_DEVICE_PERSISTENT:
> + for_device = true;
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> pgdat = NODE_DATA(nid);
>
> zone = pgdat->node_zones +
> zone_for_memory(nid, start, size, ZONE_NORMAL, for_device);
> ret = __add_pages(nid, zone, start_pfn, nr_pages);
> -
> if (ret)
> printk("%s: Problem encountered in __add_pages() as ret=%d\n",
> __func__, ret);
> @@ -667,13 +683,27 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> }
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> -int arch_remove_memory(u64 start, u64 size)
> +int arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> struct zone *zone;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + case MEMORY_DEVICE_PERSISTENT:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> zone = page_zone(pfn_to_page(start_pfn));
> ret = __remove_pages(zone, start_pfn, nr_pages);
> if (ret)
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 5f84433..0933261 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -126,14 +126,31 @@ int __weak remove_section_mapping(unsigned long start, unsigned long end)
> return -ENODEV;
> }
>
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> struct pglist_data *pgdata;
> - struct zone *zone;
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + bool for_device = false;
> + struct zone *zone;
> int rc;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + case MEMORY_DEVICE_PERSISTENT:
> + for_device = true;
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> pgdata = NODE_DATA(nid);
>
> start = (unsigned long)__va(start);
> @@ -153,13 +170,27 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> }
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> -int arch_remove_memory(u64 start, u64 size)
> +int arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> struct zone *zone;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + case MEMORY_DEVICE_PERSISTENT:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> zone = page_zone(pfn_to_page(start_pfn));
> ret = __remove_pages(zone, start_pfn, nr_pages);
> if (ret)
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index bf5b8a0..20d7714 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -153,7 +153,7 @@ void __init free_initrd_mem(unsigned long start, unsigned long end)
> #endif
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> unsigned long zone_start_pfn, zone_end_pfn, nr_pages;
> unsigned long start_pfn = PFN_DOWN(start);
> @@ -162,6 +162,18 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> struct zone *zone;
> int rc, i;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> rc = vmem_add_mapping(start, size);
> if (rc)
> return rc;
> @@ -205,7 +217,7 @@ unsigned long memory_block_size_bytes(void)
> }
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> -int arch_remove_memory(u64 start, u64 size)
> +int arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> /*
> * There is no hardware or firmware interface which could trigger a
> diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
> index 7549186..f37e7a6 100644
> --- a/arch/sh/mm/init.c
> +++ b/arch/sh/mm/init.c
> @@ -485,13 +485,30 @@ void free_initrd_mem(unsigned long start, unsigned long end)
> #endif
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> pg_data_t *pgdat;
> unsigned long start_pfn = PFN_DOWN(start);
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + bool for_device = false;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + case MEMORY_DEVICE_PERSISTENT:
> + for_device = true;
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> pgdat = NODE_DATA(nid);
>
> /* We only have ZONE_NORMAL, so this is easy.. */
> @@ -516,13 +533,27 @@ EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
> #endif
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> -int arch_remove_memory(u64 start, u64 size)
> +int arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> unsigned long start_pfn = PFN_DOWN(start);
> unsigned long nr_pages = size >> PAGE_SHIFT;
> struct zone *zone;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + case MEMORY_DEVICE_PERSISTENT:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> zone = page_zone(pfn_to_page(start_pfn));
> ret = __remove_pages(zone, start_pfn, nr_pages);
> if (unlikely(ret))
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index c68078f..811d631 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -826,24 +826,57 @@ void __init mem_init(void)
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> struct pglist_data *pgdata = NODE_DATA(nid);
> - struct zone *zone = pgdata->node_zones +
> - zone_for_memory(nid, start, size, ZONE_HIGHMEM, for_device);
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + bool for_device = false;
> + struct zone *zone;
> +
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + case MEMORY_DEVICE_PERSISTENT:
> + for_device = true;
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> + zone = pgdata->node_zones +
> + zone_for_memory(nid, start, size, ZONE_HIGHMEM, for_device);
>
> return __add_pages(nid, zone, start_pfn, nr_pages);
> }
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> -int arch_remove_memory(u64 start, u64 size)
> +int arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> struct zone *zone;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type. In particular, MEMORY_DEVICE_UNADDRESSABLE
> + * is not supported on this architecture.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + case MEMORY_DEVICE_PERSISTENT:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> zone = page_zone(pfn_to_page(start_pfn));
> return __remove_pages(zone, start_pfn, nr_pages);
> }
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 7eef172..6c0b24e 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -641,15 +641,33 @@ static void update_end_of_memory_vars(u64 start, u64 size)
> * Memory is added always to NORMAL zone. This means you will never get
> * additional DMA/DMA32 memory.
> */
> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> +int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type)
> {
> struct pglist_data *pgdat = NODE_DATA(nid);
> - struct zone *zone = pgdat->node_zones +
> - zone_for_memory(nid, start, size, ZONE_NORMAL, for_device);
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + bool for_device = false;
> + struct zone *zone;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + break;
> + case MEMORY_DEVICE_PERSISTENT:
> + for_device = true;
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> + zone = pgdat->node_zones +
> + zone_for_memory(nid, start, size, ZONE_NORMAL, for_device);
> +
> init_memory_mapping(start, start + size);
>
> ret = __add_pages(nid, zone, start_pfn, nr_pages);
> @@ -946,7 +964,7 @@ kernel_physical_mapping_remove(unsigned long start, unsigned long end)
> remove_pagetable(start, end, true);
> }
>
> -int __ref arch_remove_memory(u64 start, u64 size)
> +int __ref arch_remove_memory(u64 start, u64 size, enum memory_type type)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> @@ -955,6 +973,19 @@ int __ref arch_remove_memory(u64 start, u64 size)
> struct zone *zone;
> int ret;
>
> + /*
> + * Each memory_type needs special handling, so error out on an
> + * unsupported type.
> + */
> + switch (type) {
> + case MEMORY_NORMAL:
> + case MEMORY_DEVICE_PERSISTENT:
> + break;
> + default:
> + pr_err("hotplug unsupported memory type %d\n", type);
> + return -EINVAL;
> + }
> +
> /* With altmap the first mapped page is offset from @start */
> altmap = to_vmem_altmap((unsigned long) page);
> if (altmap)
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 134a2f6..c3999f2 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -13,6 +13,26 @@ struct mem_section;
> struct memory_block;
> struct resource;
>
> +/*
> + * When hotplugging memory with arch_add_memory(), we want more information on
> + * the type of memory we are hotplugging, because depending on the type of
> + * architecture, the code might want to take different paths.
> + *
> + * MEMORY_NORMAL:
> + * Your regular system memory. Default common case.
> + *
> + * MEMORY_DEVICE_PERSISTENT:
> + * Persistent device memory (pmem): struct page might be allocated in different
> + * memory and architecture might want to perform special actions. It is similar
> + * to regular memory, in that the CPU can access it transparently. However,
> + * it is likely to have different bandwidth and latency than regular memory.
> + * See Documentation/nvdimm/nvdimm.txt for more information.
> + */
> +enum memory_type {
> + MEMORY_NORMAL = 0,
> + MEMORY_DEVICE_PERSISTENT,
> +};
> +
> #ifdef CONFIG_MEMORY_HOTPLUG
>
> /*
> @@ -104,7 +124,7 @@ extern bool memhp_auto_online;
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
> extern bool is_pageblock_removable_nolock(struct page *page);
> -extern int arch_remove_memory(u64 start, u64 size);
> +extern int arch_remove_memory(u64 start, u64 size, enum memory_type type);
> extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
> unsigned long nr_pages);
> #endif /* CONFIG_MEMORY_HOTREMOVE */
> @@ -276,7 +296,7 @@ extern int add_memory(int nid, u64 start, u64 size);
> extern int add_memory_resource(int nid, struct resource *resource, bool online);
> extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
> bool for_device);
> -extern int arch_add_memory(int nid, u64 start, u64 size, bool for_device);
> +extern int arch_add_memory(int nid, u64 start, u64 size, enum memory_type type);
> extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
> extern bool is_memblock_offlined(struct memory_block *mem);
> extern void remove_memory(int nid, u64 start, u64 size);
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index 9341619..1f720f7 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -41,12 +41,14 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
> * @res: physical address range covered by @ref
> * @ref: reference count that pins the devm_memremap_pages() mapping
> * @dev: host device of the mapping for debug
> + * @type: memory type see MEMORY_* in memory_hotplug.h
> */
> struct dev_pagemap {
> struct vmem_altmap *altmap;
> const struct resource *res;
> struct percpu_ref *ref;
> struct device *dev;
> + enum memory_type type;
> };
>
> #ifdef CONFIG_ZONE_DEVICE
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 07e85e5..6b4505d 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -248,7 +248,7 @@ static void devm_memremap_pages_release(struct device *dev, void *data)
> align_size = ALIGN(resource_size(res), SECTION_SIZE);
>
> mem_hotplug_begin();
> - arch_remove_memory(align_start, align_size);
> + arch_remove_memory(align_start, align_size, pgmap->type);
> mem_hotplug_done();
>
> untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
> @@ -326,6 +326,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
> }
> pgmap->ref = ref;
> pgmap->res = &page_map->res;
> + pgmap->type = MEMORY_DEVICE_PERSISTENT;
>
> mutex_lock(&pgmap_lock);
> error = 0;
> @@ -363,7 +364,7 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
> goto err_pfn_remap;
>
> mem_hotplug_begin();
> - error = arch_add_memory(nid, align_start, align_size, true);
> + error = arch_add_memory(nid, align_start, align_size, pgmap->type);
> mem_hotplug_done();
> if (error)
> goto err_add_memory;
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index a07a07c..d1a4326 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1384,7 +1384,7 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
> }
>
> /* call arch's memory hotadd */
> - ret = arch_add_memory(nid, start, size, false);
> + ret = arch_add_memory(nid, start, size, MEMORY_NORMAL);
>
> if (ret < 0)
> goto error;
> @@ -2188,7 +2188,7 @@ void __ref remove_memory(int nid, u64 start, u64 size)
> memblock_free(start, size);
> memblock_remove(start, size);
>
> - arch_remove_memory(start, size);
> + arch_remove_memory(start, size, MEMORY_NORMAL);
>
> try_offline_node(nid);
>
> --
> 2.9.3
>
> --
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--
Michal Hocko
SUSE Labs