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[PATCH] SHM_NORESERVE flags for shmget()

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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 <pbadari@us.ibm.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Badari Pulavarty 2005-11-07 00:59:27 -08:00 committed by Linus Torvalds
parent d8ba3b7310
commit bf8f972d3a
2 changed files with 10 additions and 1 deletions
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1
include/linux/shm.h
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@ -92,6 +92,7 @@ struct shmid_kernel /* private to the kernel */
#define SHM_DEST 01000 /* segment will be destroyed on last detach */ #define SHM_DEST 01000 /* segment will be destroyed on last detach */
#define SHM_LOCKED 02000 /* segment will not be swapped */ #define SHM_LOCKED 02000 /* segment will not be swapped */
#define SHM_HUGETLB 04000 /* segment will use huge TLB pages */ #define SHM_HUGETLB 04000 /* segment will use huge TLB pages */
#define SHM_NORESERVE 010000 /* don't check for reservations */
#ifdef CONFIG_SYSVIPC #ifdef CONFIG_SYSVIPC
long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr); long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr);

10
ipc/shm.c
View file

@ -212,8 +212,16 @@ static int newseg (key_t key, int shmflg, size_t size)
file = hugetlb_zero_setup(size); file = hugetlb_zero_setup(size);
shp->mlock_user = current->user; shp->mlock_user = current->user;
} else { } 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); sprintf (name, "SYSV%08x", key);
file = shmem_file_setup(name, size, VM_ACCOUNT); file = shmem_file_setup(name, size, acctflag);
} }
error = PTR_ERR(file); error = PTR_ERR(file);
if (IS_ERR(file)) if (IS_ERR(file))