diff options
| author | Michael S. Tsirkin <mst@mellanox.co.il> | 2006-02-15 00:53:08 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-15 03:09:34 +0300 |
| commit | f822566165dd46ff5de9bf895cfa6c51f53bb0c4 (patch) | |
| tree | e052f406d5a14140d17f76dc8914d33bbc8e5f1d /include/asm-parisc | |
| parent | 8861da31e3b3e3df7b05e7b157230de3d486e53b (diff) | |
| download | linux-f822566165dd46ff5de9bf895cfa6c51f53bb0c4.tar.xz | |
[PATCH] madvise MADV_DONTFORK/MADV_DOFORK
Currently, copy-on-write may change the physical address of a page even if the
user requested that the page is pinned in memory (either by mlock or by
get_user_pages). This happens if the process forks meanwhile, and the parent
writes to that page. As a result, the page is orphaned: in case of
get_user_pages, the application will never see any data hardware DMA's into
this page after the COW. In case of mlock'd memory, the parent is not getting
the realtime/security benefits of mlock.
In particular, this affects the Infiniband modules which do DMA from and into
user pages all the time.
This patch adds madvise options to control whether memory range is inherited
across fork. Useful e.g. for when hardware is doing DMA from/into these
pages. Could also be useful to an application wanting to speed up its forks
by cutting large areas out of consideration.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Acked-by: Hugh Dickins <hugh@veritas.com>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-parisc')
| -rw-r--r-- | include/asm-parisc/mman.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/asm-parisc/mman.h b/include/asm-parisc/mman.h index 736b0abcac05..a381cf5c8f55 100644 --- a/include/asm-parisc/mman.h +++ b/include/asm-parisc/mman.h @@ -49,6 +49,8 @@ #define MADV_4M_PAGES 22 /* Use 4 Megabyte pages */ #define MADV_16M_PAGES 24 /* Use 16 Megabyte pages */ #define MADV_64M_PAGES 26 /* Use 64 Megabyte pages */ +#define MADV_DONTFORK 0x30 /* dont inherit across fork */ +#define MADV_DOFORK 0x31 /* do inherit across fork */ /* compatibility flags */ #define MAP_ANON MAP_ANONYMOUS |