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    Subject[PATCH v2 5/7] mm,memory_hotplug: Enforce pageblock alignment when memmap_on_memory
    Date
    Many places expects us to pass a pageblock aligned range.
    E.g: memmap_init_zone() needs a pageblock aligned range in order
    to set the proper migrate type for it.
    online_pages() needs to operate on a pageblock aligned range for
    isolation purposes.

    Make sure we disable the feature in case we cannot guarantee the
    right alignment.

    Signed-off-by: Oscar Salvador <osalvador@suse.de>
    ---
    mm/memory_hotplug.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
    index d3fb036d33fd..1a4d5dd1a2c8 100644
    --- a/mm/memory_hotplug.c
    +++ b/mm/memory_hotplug.c
    @@ -56,12 +56,16 @@ static int memmap_on_memory_show(char *buffer, const struct kernel_param *kp)
    static __meminit int memmap_on_memory_store(const char *val,
    const struct kernel_param *kp)
    {
    + unsigned long pageblock_size = PFN_PHYS(pageblock_nr_pages);
    +
    /*
    * Fail silently in case we cannot enable it due to system constraints.
    * User can always check whether it is enabled or not via /sys/module.
    */
    if (!IS_ENABLED(CONFIG_ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE) ||
    - (PMD_SIZE % sizeof(struct page)))
    + (PMD_SIZE % sizeof(struct page)) ||
    + !(MIN_MEMORY_BLOCK_SIZE - PMD_SIZE) ||
    + !(MIN_MEMORY_BLOCK_SIZE - PMD_SIZE) % pageblock_size)
    return 0;

    return param_set_bool(val, kp);
    --
    2.16.3
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