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    SubjectRe: [PATCH x86,mm] fix pgt_buf_end when memory hotplug
    On Thu, 8 Sep 2011, Lai Jiangshan wrote:
    >
    > When I test memory hotplug, such message is always outputted when hot-adding
    > a memory block:
    >
    > initial kernel pagetable allocation wasted ffffffffffffffff pages

    I take you are using tip/x86/mm, because that is the only branch that
    contains that warning.


    > This message comes from init_memory_mapping(), it shows "pgt_buf_end" is
    > incorrect here, and I found it was caused by alloc_low_page().
    >
    > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
    > ---
    > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
    > index bbaaa00..e138e0a 100644
    > --- a/arch/x86/mm/init_64.c
    > +++ b/arch/x86/mm/init_64.c
    > @@ -317,7 +317,7 @@ void __init cleanup_highmap(void)
    >
    > static __ref void *alloc_low_page(unsigned long *phys)
    > {
    > - unsigned long pfn = pgt_buf_end++;
    > + unsigned long pfn;
    > void *adr;
    >
    > if (after_bootmem) {
    > @@ -327,6 +327,7 @@ static __ref void *alloc_low_page(unsigned long *phys)
    > return adr;
    > }
    >
    > + pfn = pgt_buf_end++;
    > if (pfn >= pgt_buf_top)
    > panic("alloc_low_page: ran out of memory");


    This patch makes sense to me. It would also make sense to print the
    "allocation wasted" warning only if (!after_bootmem).


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