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

Michal Hocko
2017-08-01T09:01:04Z

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@infradead.org>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> 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