On Wed, Aug 16, 2017 at 9:47 AM, Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote: > On Wed, Aug 16, 2017 at 09:35:11AM -0700, Dan Williams wrote: >> On Wed, Aug 16, 2017 at 4:15 AM, Kirill A. Shutemov >> <kirill@xxxxxxxxxxxxx> wrote: >> > On Wed, Aug 16, 2017 at 12:44:22AM -0700, Dan Williams wrote: >> >> diff --git a/include/linux/mman.h b/include/linux/mman.h >> >> index c8367041fafd..0e1de42c836f 100644 >> >> --- a/include/linux/mman.h >> >> +++ b/include/linux/mman.h >> >> @@ -7,6 +7,40 @@ >> >> #include <linux/atomic.h> >> >> #include <uapi/linux/mman.h> >> >> >> >> +#ifndef MAP_32BIT >> >> +#define MAP_32BIT 0 >> >> +#endif >> >> +#ifndef MAP_HUGE_2MB >> >> +#define MAP_HUGE_2MB 0 >> >> +#endif >> >> +#ifndef MAP_HUGE_1GB >> >> +#define MAP_HUGE_1GB 0 >> >> +#endif >> >> + >> >> +/* >> >> + * The historical set of flags that all mmap implementations implicitly >> >> + * support when file_operations.mmap_supported_mask is zero. >> >> + */ >> >> +#define LEGACY_MAP_SUPPORTED_MASK (MAP_SHARED \ >> >> + | MAP_PRIVATE \ >> >> + | MAP_FIXED \ >> >> + | MAP_ANONYMOUS \ >> >> + | MAP_UNINITIALIZED \ >> >> + | MAP_GROWSDOWN \ >> >> + | MAP_DENYWRITE \ >> >> + | MAP_EXECUTABLE \ >> >> + | MAP_LOCKED \ >> >> + | MAP_NORESERVE \ >> >> + | MAP_POPULATE \ >> >> + | MAP_NONBLOCK \ >> >> + | MAP_STACK \ >> >> + | MAP_HUGETLB \ >> >> + | MAP_32BIT \ >> >> + | MAP_HUGE_2MB \ >> >> + | MAP_HUGE_1GB) >> >> + >> >> +#define MAP_SUPPORTED_MASK (LEGACY_MAP_SUPPORTED_MASK) >> >> + >> >> extern int sysctl_overcommit_memory; >> >> extern int sysctl_overcommit_ratio; >> >> extern unsigned long sysctl_overcommit_kbytes; >> > >> > Since we looking into mmap(2) ABI, maybe we should consider re-defining >> > MAP_DENYWRITE and MAP_EXECUTABLE as 0 in hope that we would be able to >> > re-use these bits in the future? These flags are ignored now anyway. >> >> Yes, we can make these -EOPNOTSUPP in the new syscall. > > You cannot detect them, if we would redefine them as 0. :) Yes, we can, there will now be missing bits in LEGACY_MAP_SUPPORTED_MASK that will fail those bit values until we re-define them. Everything else is a an exercise for libc about what it wants to do when it sees those values. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
