From bf8f972d3a1daf969cf44f64cc36d53bfd76441f Mon Sep 17 00:00:00 2001 From: Badari Pulavarty Date: Mon, 7 Nov 2005 00:59:27 -0800 Subject: [PATCH] [PATCH] SHM_NORESERVE flags for shmget() Add SHM_NORESERVE functionality similar to MAP_NORESERVE for shared memory segments. This is mainly to avoid abuse of OVERCOMMIT_ALWAYS and this flag is ignored for OVERCOMMIT_NEVER. Signed-off-by: Badari Pulavarty Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/shm.h | 1 + ipc/shm.c | 10 +++++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/include/linux/shm.h b/include/linux/shm.h index 80113a1f60b..a2c896ad0be 100644 --- a/include/linux/shm.h +++ b/include/linux/shm.h @@ -92,6 +92,7 @@ struct shmid_kernel /* private to the kernel */ #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 */ #ifdef CONFIG_SYSVIPC long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr); diff --git a/ipc/shm.c b/ipc/shm.c index b58c651d31a..587d836d80d 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -212,8 +212,16 @@ static int newseg (key_t key, int shmflg, size_t size) file = hugetlb_zero_setup(size); shp->mlock_user = current->user; } else { + int acctflag = VM_ACCOUNT; + /* + * Do not allow no accounting for OVERCOMMIT_NEVER, even + * if it's asked for. + */ + if ((shmflg & SHM_NORESERVE) && + sysctl_overcommit_memory != OVERCOMMIT_NEVER) + acctflag = 0; sprintf (name, "SYSV%08x", key); - file = shmem_file_setup(name, size, VM_ACCOUNT); + file = shmem_file_setup(name, size, acctflag); } error = PTR_ERR(file); if (IS_ERR(file)) -- 2.20.1