Re: [PATCH 3/3] mm:shm: Use new hugetlb size encoding definitions

[Michal Hocko]

On Mon 31-07-17 11:56:26, Mike Kravetz wrote:
> Use the common definitions from hugetlb_encode.h header file for
> encoding hugetlb size definitions in shmget system call flags.
> 
> In addition, move these definitions from the internal (kernel) to
> user (uapi) header file.
> 
> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  include/linux/shm.h      | 17 -----------------
>  include/uapi/linux/shm.h | 31 +++++++++++++++++++++++++++++--
>  2 files changed, 29 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/shm.h b/include/linux/shm.h
> index 04e8818..d56285a 100644
> --- a/include/linux/shm.h
> +++ b/include/linux/shm.h
> @@ -27,23 +27,6 @@ struct shmid_kernel /* private to the kernel */
>  /* shm_mode upper byte flags */
>  #define	SHM_DEST	01000	/* segment will be destroyed on last detach */
>  #define SHM_LOCKED      02000   /* segment will not be swapped */
> -#define SHM_HUGETLB     04000   /* segment will use huge TLB pages */
> -#define SHM_NORESERVE   010000  /* don't check for reservations */
> -
> -/* Bits [26:31] are reserved */
> -
> -/*
> - * When SHM_HUGETLB is set bits [26:31] encode the log2 of the huge page size.
> - * This gives us 6 bits, which is enough until someone invents 128 bit address
> - * spaces.
> - *
> - * Assume these are all power of twos.
> - * When 0 use the default page size.
> - */
> -#define SHM_HUGE_SHIFT  26
> -#define SHM_HUGE_MASK   0x3f
> -#define SHM_HUGE_2MB    (21 << SHM_HUGE_SHIFT)
> -#define SHM_HUGE_1GB    (30 << SHM_HUGE_SHIFT)
>  
>  #ifdef CONFIG_SYSVIPC
>  struct sysv_shm {
> diff --git a/include/uapi/linux/shm.h b/include/uapi/linux/shm.h
> index 1fbf24e..cf23c87 100644
> --- a/include/uapi/linux/shm.h
> +++ b/include/uapi/linux/shm.h
> @@ -3,6 +3,7 @@
>  
>  #include <linux/ipc.h>
>  #include <linux/errno.h>
> +#include <asm-generic/hugetlb_encode.h>
>  #ifndef __KERNEL__
>  #include <unistd.h>
>  #endif
> @@ -40,11 +41,37 @@ struct shmid_ds {
>  /* Include the definition of shmid64_ds and shminfo64 */
>  #include <asm/shmbuf.h>
>  
> -/* permission flag for shmget */
> +/*
> + * shmget() shmflg values.
> + */
> +/* The bottom nine bits are the same as open(2) mode flags */
>  #define SHM_R		0400	/* or S_IRUGO from <linux/stat.h> */
>  #define SHM_W		0200	/* or S_IWUGO from <linux/stat.h> */
> +/* Bits 9 & 10 are IPC_CREAT and IPC_EXCL */
> +#define SHM_HUGETLB	04000	/* segment will use huge TLB pages */
> +#define SHM_NORESERVE	010000	/* don't check for reservations */
> +
> +/*
> + * Huge page size encoding when SHM_HUGETLB is specified, and a huge page
> + * size other than the default is desired.  See hugetlb_encode.h
> + */
> +#define SHM_HUGE_SHIFT	HUGETLB_FLAG_ENCODE_SHIFT
> +#define SHM_HUGE_MASK	HUGETLB_FLAG_ENCODE_MASK
> +
> +#define SHM_HUGE_64KB	HUGETLB_FLAG_ENCODE_64KB
> +#define SHM_HUGE_512KB	HUGETLB_FLAG_ENCODE_512KB
> +#define SHM_HUGE_1MB	HUGETLB_FLAG_ENCODE_1MB
> +#define SHM_HUGE_2MB	HUGETLB_FLAG_ENCODE_2MB
> +#define SHM_HUGE_8MB	HUGETLB_FLAG_ENCODE_8MB
> +#define SHM_HUGE_16MB	HUGETLB_FLAG_ENCODE_16MB
> +#define SHM_HUGE_256MB	HUGETLB_FLAG_ENCODE_256MB
> +#define SHM_HUGE_1GB	HUGETLB_FLAG_ENCODE_1GB
> +#define SHM_HUGE_2GB	HUGETLB_FLAG_ENCODE_2GB
> +#define SHM_HUGE_16GB	HUGETLB_FLAG_ENCODE_16GB
>  
> -/* mode for attach */
> +/*
> + * shmat() shmflg values
> + */
>  #define	SHM_RDONLY	010000	/* read-only access */
>  #define	SHM_RND		020000	/* round attach address to SHMLBA boundary */
>  #define	SHM_REMAP	040000	/* take-over region on attach */
> -- 
> 2.7.5

-- 
Michal Hocko
SUSE Labs