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    Subject[PATCH 03/27] Xen: Rename the balloon lock
    Date
    From: Alex Nixon <alex.nixon@citrix.com>

    * xen_create_contiguous_region needs access to the balloon lock to
    ensure memory doesn't change under its feet, so expose the balloon
    lock
    * Change the name of the lock to xen_reservation_lock, to imply it's
    now less-specific usage.

    Signed-off-by: Alex Nixon <alex.nixon@citrix.com>
    ---
    arch/x86/xen/mmu.c | 7 +++++++
    drivers/xen/balloon.c | 15 ++++-----------
    include/xen/interface/memory.h | 8 ++++++++
    3 files changed, 19 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
    index 58af0b0..c2aa44b 100644
    --- a/arch/x86/xen/mmu.c
    +++ b/arch/x86/xen/mmu.c
    @@ -67,6 +67,13 @@

    #define MMU_UPDATE_HISTO 30

    +/*
    + * Protects atomic reservation decrease/increase against concurrent increases.
    + * Also protects non-atomic updates of current_pages and driver_pages, and
    + * balloon lists.
    + */
    +DEFINE_SPINLOCK(xen_reservation_lock);
    +
    #ifdef CONFIG_XEN_DEBUG_FS

    static struct {
    diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
    index efa4b36..1e7984d 100644
    --- a/drivers/xen/balloon.c
    +++ b/drivers/xen/balloon.c
    @@ -84,13 +84,6 @@ static struct sys_device balloon_sysdev;

    static int register_balloon(struct sys_device *sysdev);

    -/*
    - * Protects atomic reservation decrease/increase against concurrent increases.
    - * Also protects non-atomic updates of current_pages and driver_pages, and
    - * balloon lists.
    - */
    -static DEFINE_SPINLOCK(balloon_lock);
    -
    static struct balloon_stats balloon_stats;

    /* We increase/decrease in batches which fit in a page */
    @@ -209,7 +202,7 @@ static int increase_reservation(unsigned long nr_pages)
    if (nr_pages > ARRAY_SIZE(frame_list))
    nr_pages = ARRAY_SIZE(frame_list);

    - spin_lock_irqsave(&balloon_lock, flags);
    + spin_lock_irqsave(&xen_reservation_lock, flags);

    page = balloon_first_page();
    for (i = 0; i < nr_pages; i++) {
    @@ -267,7 +260,7 @@ static int increase_reservation(unsigned long nr_pages)
    totalram_pages = balloon_stats.current_pages;

    out:
    - spin_unlock_irqrestore(&balloon_lock, flags);
    + spin_unlock_irqrestore(&xen_reservation_lock, flags);

    return 0;
    }
    @@ -312,7 +305,7 @@ static int decrease_reservation(unsigned long nr_pages)
    kmap_flush_unused();
    flush_tlb_all();

    - spin_lock_irqsave(&balloon_lock, flags);
    + spin_lock_irqsave(&xen_reservation_lock, flags);

    /* No more mappings: invalidate P2M and add to balloon. */
    for (i = 0; i < nr_pages; i++) {
    @@ -329,7 +322,7 @@ static int decrease_reservation(unsigned long nr_pages)
    balloon_stats.current_pages -= nr_pages;
    totalram_pages = balloon_stats.current_pages;

    - spin_unlock_irqrestore(&balloon_lock, flags);
    + spin_unlock_irqrestore(&xen_reservation_lock, flags);

    return need_sleep;
    }
    diff --git a/include/xen/interface/memory.h b/include/xen/interface/memory.h
    index f548f7c..9df4bd0 100644
    --- a/include/xen/interface/memory.h
    +++ b/include/xen/interface/memory.h
    @@ -9,6 +9,8 @@
    #ifndef __XEN_PUBLIC_MEMORY_H__
    #define __XEN_PUBLIC_MEMORY_H__

    +#include <linux/spinlock.h>
    +
    /*
    * Increase or decrease the specified domain's memory reservation. Returns a
    * -ve errcode on failure, or the # extents successfully allocated or freed.
    @@ -184,4 +186,10 @@ DEFINE_GUEST_HANDLE_STRUCT(xen_memory_map);
    */
    #define XENMEM_machine_memory_map 10

    +/*
    + * Prevent the balloon driver from changing the memory reservation during a driver
    + * critical region.
    + */
    +extern spinlock_t xen_reservation_lock;
    +
    #endif /* __XEN_PUBLIC_MEMORY_H__ */
    --
    1.6.0.6


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