On 2015/06/04 22:02, Xishi Qiu wrote:
This patch introduces a new gfp flag called "__GFP_MIRROR", it is used to allocate mirrored pages through buddy system. Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
In Tony's original proposal, the motivation was to mirror all kernel memory. Is the purpose of this patch making mirrored range available for user space ? But, hmm... I don't think adding a new GFP flag is a good idea. It adds many conditional jumps. How about using GFP_KERNEL for user memory if the user wants mirrored memory with mirroring all kernel memory? Thanks, -Kame
--- include/linux/gfp.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 15928f0..89d0091 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -35,6 +35,7 @@ struct vm_area_struct; #define ___GFP_NO_KSWAPD 0x400000u #define ___GFP_OTHER_NODE 0x800000u #define ___GFP_WRITE 0x1000000u +#define ___GFP_MIRROR 0x2000000u /* If the above are modified, __GFP_BITS_SHIFT may need updating */ /* @@ -95,13 +96,15 @@ struct vm_area_struct; #define __GFP_OTHER_NODE ((__force gfp_t)___GFP_OTHER_NODE) /* On behalf of other node */ #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) /* Allocator intends to dirty page */ +#define __GFP_MIRROR ((__force gfp_t)___GFP_MIRROR) /* Allocate mirrored memory */ + /* * This may seem redundant, but it's a way of annotating false positives vs. * allocations that simply cannot be supported (e.g. page tables). */ #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK) -#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */ +#define __GFP_BITS_SHIFT 26 /* Room for N __GFP_FOO bits */ #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) /* This equals 0, but use constants in case they ever change */
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