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    Subject[PATCH 6/9] mm: __GFP_EMERGENCY
    __GFP_EMERGENCY will allow the allocation to disregard the watermarks, 
    much like PF_MEMALLOC.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/linux/gfp.h | 7 ++++++-
    mm/internal.h | 10 +++++++---
    2 files changed, 13 insertions(+), 4 deletions(-)

    Index: linux-2.6-git/include/linux/gfp.h
    ===================================================================
    --- linux-2.6-git.orig/include/linux/gfp.h 2006-12-14 10:02:18.000000000 +0100
    +++ linux-2.6-git/include/linux/gfp.h 2006-12-14 10:02:52.000000000 +0100
    @@ -35,17 +35,21 @@ struct vm_area_struct;
    #define __GFP_HIGH ((__force gfp_t)0x20u) /* Should access emergency pools? */
    #define __GFP_IO ((__force gfp_t)0x40u) /* Can start physical IO? */
    #define __GFP_FS ((__force gfp_t)0x80u) /* Can call down to low-level FS? */
    +
    #define __GFP_COLD ((__force gfp_t)0x100u) /* Cache-cold page required */
    #define __GFP_NOWARN ((__force gfp_t)0x200u) /* Suppress page allocation failure warning */
    #define __GFP_REPEAT ((__force gfp_t)0x400u) /* Retry the allocation. Might fail */
    #define __GFP_NOFAIL ((__force gfp_t)0x800u) /* Retry for ever. Cannot fail */
    +
    #define __GFP_NORETRY ((__force gfp_t)0x1000u)/* Do not retry. Might fail */
    #define __GFP_NO_GROW ((__force gfp_t)0x2000u)/* Slab internal usage */
    #define __GFP_COMP ((__force gfp_t)0x4000u)/* Add compound page metadata */
    #define __GFP_ZERO ((__force gfp_t)0x8000u)/* Return zeroed page on success */
    +
    #define __GFP_NOMEMALLOC ((__force gfp_t)0x10000u) /* Don't use emergency reserves */
    #define __GFP_HARDWALL ((__force gfp_t)0x20000u) /* Enforce hardwall cpuset memory allocs */
    #define __GFP_THISNODE ((__force gfp_t)0x40000u)/* No fallback, no policies */
    +#define __GFP_EMERGENCY ((__force gfp_t)0x80000u) /* Use emergency reserves */

    #define __GFP_BITS_SHIFT 20 /* Room for 20 __GFP_FOO bits */
    #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
    @@ -54,7 +58,8 @@ struct vm_area_struct;
    #define GFP_LEVEL_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS| \
    __GFP_COLD|__GFP_NOWARN|__GFP_REPEAT| \
    __GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP| \
    - __GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE)
    + __GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE| \
    + __GFP_EMERGENCY)

    /* This equals 0, but use constants in case they ever change */
    #define GFP_NOWAIT (GFP_ATOMIC & ~__GFP_HIGH)
    Index: linux-2.6-git/mm/internal.h
    ===================================================================
    --- linux-2.6-git.orig/mm/internal.h 2006-12-14 10:02:52.000000000 +0100
    +++ linux-2.6-git/mm/internal.h 2006-12-14 10:02:52.000000000 +0100
    @@ -75,7 +75,9 @@ static int inline gfp_to_alloc_flags(gfp
    alloc_flags |= ALLOC_HARDER;

    if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
    - if (!in_irq() && (p->flags & PF_MEMALLOC))
    + if (gfp_mask & __GFP_EMERGENCY)
    + alloc_flags |= ALLOC_NO_WATERMARKS;
    + else if (!in_irq() && (p->flags & PF_MEMALLOC))
    alloc_flags |= ALLOC_NO_WATERMARKS;
    else if (!in_interrupt() &&
    unlikely(test_thread_flag(TIF_MEMDIE)))
    @@ -103,7 +105,7 @@ static inline int alloc_flags_to_rank(in
    return rank;
    }

    -static inline int gfp_to_rank(gfp_t gfp_mask)
    +static __always_inline int gfp_to_rank(gfp_t gfp_mask)
    {
    /*
    * Although correct this full version takes a ~3% performance
    @@ -118,7 +120,9 @@ static inline int gfp_to_rank(gfp_t gfp_
    */

    if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
    - if (!in_irq() && (current->flags & PF_MEMALLOC))
    + if (gfp_mask & __GFP_EMERGENCY)
    + return 0;
    + else if (!in_irq() && (current->flags & PF_MEMALLOC))
    return 0;
    else if (!in_interrupt() &&
    unlikely(test_thread_flag(TIF_MEMDIE)))
    --

    -
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