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    Subject[PATCH 4/9] mm, memory_hotplug: get rid of is_zone_device_section
    Date
    From: Michal Hocko <mhocko@suse.com>

    device memory hotplug hooks into regular memory hotplug only half way.
    It needs memory sections to track struct pages but there is no
    need/desire to associate those sections with memory blocks and export
    them to the userspace via sysfs because they cannot be onlined anyway.

    This is currently expressed by for_device argument to arch_add_memory
    which then makes sure to associate the given memory range with
    ZONE_DEVICE. register_new_memory then relies on is_zone_device_section
    to distinguish special memory hotplug from the regular one. While this
    works now, later patches in this series want to move __add_zone outside
    of arch_add_memory path so we have to come up with something else.

    Add want_memblock down the __add_pages path and use it to control
    whether the section->memblock association should be done. arch_add_memory
    then just trivially want memblock for everything but for_device hotplug.

    remove_memory_section doesn't need is_zone_device_section either. We can
    simply skip all the memblock specific cleanup if there is no memblock
    for the given section.

    This shouldn't introduce any functional change.

    Cc: Dan Williams <dan.j.williams@gmail.com>
    Signed-off-by: Michal Hocko <mhocko@suse.com>
    ---
    arch/ia64/mm/init.c | 2 +-
    arch/powerpc/mm/mem.c | 2 +-
    arch/s390/mm/init.c | 2 +-
    arch/sh/mm/init.c | 2 +-
    arch/x86/mm/init_32.c | 2 +-
    arch/x86/mm/init_64.c | 2 +-
    drivers/base/memory.c | 22 ++++++++--------------
    include/linux/memory_hotplug.h | 2 +-
    mm/memory_hotplug.c | 11 +++++++----
    9 files changed, 22 insertions(+), 25 deletions(-)

    diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
    index 06cdaef54b2e..62085fd902e6 100644
    --- a/arch/ia64/mm/init.c
    +++ b/arch/ia64/mm/init.c
    @@ -657,7 +657,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)

    zone = pgdat->node_zones +
    zone_for_memory(nid, start, size, ZONE_NORMAL, for_device);
    - ret = __add_pages(nid, zone, start_pfn, nr_pages);
    + ret = __add_pages(nid, zone, start_pfn, nr_pages, !for_device);

    if (ret)
    printk("%s: Problem encountered in __add_pages() as ret=%d\n",
    diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
    index 5f844337de21..ea3e09a62f38 100644
    --- a/arch/powerpc/mm/mem.c
    +++ b/arch/powerpc/mm/mem.c
    @@ -149,7 +149,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
    zone = pgdata->node_zones +
    zone_for_memory(nid, start, size, 0, for_device);

    - return __add_pages(nid, zone, start_pfn, nr_pages);
    + return __add_pages(nid, zone, start_pfn, nr_pages, !for_device);
    }

    #ifdef CONFIG_MEMORY_HOTREMOVE
    diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
    index bf5b8a0c4ff7..5c84346e5211 100644
    --- a/arch/s390/mm/init.c
    +++ b/arch/s390/mm/init.c
    @@ -182,7 +182,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
    continue;
    nr_pages = (start_pfn + size_pages > zone_end_pfn) ?
    zone_end_pfn - start_pfn : size_pages;
    - rc = __add_pages(nid, zone, start_pfn, nr_pages);
    + rc = __add_pages(nid, zone, start_pfn, nr_pages, !for_device);
    if (rc)
    break;
    start_pfn += nr_pages;
    diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
    index 75491862d900..a9d57f75ae8c 100644
    --- a/arch/sh/mm/init.c
    +++ b/arch/sh/mm/init.c
    @@ -498,7 +498,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
    ret = __add_pages(nid, pgdat->node_zones +
    zone_for_memory(nid, start, size, ZONE_NORMAL,
    for_device),
    - start_pfn, nr_pages);
    + start_pfn, nr_pages, !for_device);
    if (unlikely(ret))
    printk("%s: Failed, __add_pages() == %d\n", __func__, ret);

    diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
    index c68078fd06fd..4b0f05328af0 100644
    --- a/arch/x86/mm/init_32.c
    +++ b/arch/x86/mm/init_32.c
    @@ -834,7 +834,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
    unsigned long start_pfn = start >> PAGE_SHIFT;
    unsigned long nr_pages = size >> PAGE_SHIFT;

    - return __add_pages(nid, zone, start_pfn, nr_pages);
    + return __add_pages(nid, zone, start_pfn, nr_pages, !for_device);
    }

    #ifdef CONFIG_MEMORY_HOTREMOVE
    diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
    index 7eef17239378..39cfaee93975 100644
    --- a/arch/x86/mm/init_64.c
    +++ b/arch/x86/mm/init_64.c
    @@ -652,7 +652,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)

    init_memory_mapping(start, start + size);

    - ret = __add_pages(nid, zone, start_pfn, nr_pages);
    + ret = __add_pages(nid, zone, start_pfn, nr_pages, !for_device);
    WARN_ON_ONCE(ret);

    /* update max_pfn, max_low_pfn and high_memory */
    diff --git a/drivers/base/memory.c b/drivers/base/memory.c
    index cc4f1d0cbffe..89c15e942852 100644
    --- a/drivers/base/memory.c
    +++ b/drivers/base/memory.c
    @@ -685,14 +685,6 @@ static int add_memory_block(int base_section_nr)
    return 0;
    }

    -static bool is_zone_device_section(struct mem_section *ms)
    -{
    - struct page *page;
    -
    - page = sparse_decode_mem_map(ms->section_mem_map, __section_nr(ms));
    - return is_zone_device_page(page);
    -}
    -
    /*
    * need an interface for the VM to add new memory regions,
    * but without onlining it.
    @@ -702,9 +694,6 @@ int register_new_memory(int nid, struct mem_section *section)
    int ret = 0;
    struct memory_block *mem;

    - if (is_zone_device_section(section))
    - return 0;
    -
    mutex_lock(&mem_sysfs_mutex);

    mem = find_memory_block(section);
    @@ -741,11 +730,16 @@ static int remove_memory_section(unsigned long node_id,
    {
    struct memory_block *mem;

    - if (is_zone_device_section(section))
    - return 0;
    -
    mutex_lock(&mem_sysfs_mutex);
    +
    + /*
    + * Some users of the memory hotplug do not want/need memblock to
    + * track all sections. Skip over those.
    + */
    mem = find_memory_block(section);
    + if (!mem)
    + return 0;
    +
    unregister_mem_sect_under_nodes(mem, __section_nr(section));

    mem->section_count--;
    diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
    index 134a2f69c21a..3c8cf86201c3 100644
    --- a/include/linux/memory_hotplug.h
    +++ b/include/linux/memory_hotplug.h
    @@ -111,7 +111,7 @@ extern int __remove_pages(struct zone *zone, unsigned long start_pfn,

    /* reasonably generic interface to expand the physical pages in a zone */
    extern int __add_pages(int nid, struct zone *zone, unsigned long start_pfn,
    - unsigned long nr_pages);
    + unsigned long nr_pages, bool want_memblock);

    #ifdef CONFIG_NUMA
    extern int memory_add_physaddr_to_nid(u64 start);
    diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
    index 342332f29364..1570b3eea493 100644
    --- a/mm/memory_hotplug.c
    +++ b/mm/memory_hotplug.c
    @@ -493,7 +493,7 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
    }

    static int __meminit __add_section(int nid, struct zone *zone,
    - unsigned long phys_start_pfn)
    + unsigned long phys_start_pfn, bool want_memblock)
    {
    int ret;

    @@ -510,7 +510,10 @@ static int __meminit __add_section(int nid, struct zone *zone,
    if (ret < 0)
    return ret;

    - return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
    + if (want_memblock)
    + ret = register_new_memory(nid, __pfn_to_section(phys_start_pfn));
    +
    + return ret;
    }

    /*
    @@ -520,7 +523,7 @@ static int __meminit __add_section(int nid, struct zone *zone,
    * add the new pages.
    */
    int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
    - unsigned long nr_pages)
    + unsigned long nr_pages, bool want_memblock)
    {
    unsigned long i;
    int err = 0;
    @@ -548,7 +551,7 @@ int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
    }

    for (i = start_sec; i <= end_sec; i++) {
    - err = __add_section(nid, zone, section_nr_to_pfn(i));
    + err = __add_section(nid, zone, section_nr_to_pfn(i), want_memblock);

    /*
    * EEXIST is finally dealt with by ioresource collision
    --
    2.11.0
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