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

Mike Kravetz
2017-07-31T18:56:26Z

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>
---
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

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