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    Subject[PATCH 07/33] mm: serialize access to min_free_kbytes
    There is a small race between the procfs caller and the memory hotplug caller
    of setup_per_zone_pages_min(). Not a big deal, but the next patch will add yet
    another caller. Time to close the gap.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    mm/page_alloc.c | 16 +++++++++++++---
    1 file changed, 13 insertions(+), 3 deletions(-)

    Index: linux-2.6/mm/page_alloc.c
    ===================================================================
    --- linux-2.6.orig/mm/page_alloc.c
    +++ linux-2.6/mm/page_alloc.c
    @@ -116,6 +116,7 @@ static char * const zone_names[MAX_NR_ZO
    "Movable",
    };

    +static DEFINE_SPINLOCK(min_free_lock);
    int min_free_kbytes = 1024;

    unsigned long __meminitdata nr_kernel_pages;
    @@ -4162,12 +4163,12 @@ static void setup_per_zone_lowmem_reserv
    }

    /**
    - * setup_per_zone_pages_min - called when min_free_kbytes changes.
    + * __setup_per_zone_pages_min - called when min_free_kbytes changes.
    *
    * Ensures that the pages_{min,low,high} values for each zone are set correctly
    * with respect to min_free_kbytes.
    */
    -void setup_per_zone_pages_min(void)
    +static void __setup_per_zone_pages_min(void)
    {
    unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
    unsigned long lowmem_pages = 0;
    @@ -4222,6 +4223,15 @@ void setup_per_zone_pages_min(void)
    calculate_totalreserve_pages();
    }

    +void setup_per_zone_pages_min(void)
    +{
    + unsigned long flags;
    +
    + spin_lock_irqsave(&min_free_lock, flags);
    + __setup_per_zone_pages_min();
    + spin_unlock_irqrestore(&min_free_lock, flags);
    +}
    +
    /*
    * Initialise min_free_kbytes.
    *
    @@ -4257,7 +4267,7 @@ static int __init init_per_zone_pages_mi
    min_free_kbytes = 128;
    if (min_free_kbytes > 65536)
    min_free_kbytes = 65536;
    - setup_per_zone_pages_min();
    + __setup_per_zone_pages_min();
    setup_per_zone_lowmem_reserve();
    return 0;
    }
    --

    -
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