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Subject[PATCH v2 2/8] fcntl: Introduce new O_DENY* open flags
Date
This patch adds 4 flags:
1) O_DENYREAD that doesn't permit read access,
2) O_DENYWRITE that doesn't permit write access,
3) O_DENYDELETE that doesn't permit delete or rename,
4) O_DENYMAND that enables O_DENY* flags checks.

Network filesystems CIFS, SMB2.0, SMB3.0 and NFSv4 have such flags -
this change can benefit cifs and nfs modules as well as Samba and
NFS file servers. These flags are only take affect for opens with
O_DENYMAND flags - there is no impact on native Linux opens.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
---
fs/fcntl.c | 5 +++--
include/uapi/asm-generic/fcntl.h | 14 ++++++++++++++
2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 71a600a..d88a548 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -730,14 +730,15 @@ static int __init fcntl_init(void)
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
- BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+ BUILD_BUG_ON(23 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
O_RDONLY | O_WRONLY | O_RDWR |
O_CREAT | O_EXCL | O_NOCTTY |
O_TRUNC | O_APPEND | /* O_NONBLOCK | */
__O_SYNC | O_DSYNC | FASYNC |
O_DIRECT | O_LARGEFILE | O_DIRECTORY |
O_NOFOLLOW | O_NOATIME | O_CLOEXEC |
- __FMODE_EXEC | O_PATH
+ __FMODE_EXEC | O_PATH | O_DENYREAD |
+ O_DENYWRITE | O_DENYDELETE | O_DENYMAND
));

fasync_cache = kmem_cache_create("fasync_cache",
diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
index a48937d..6e4e979 100644
--- a/include/uapi/asm-generic/fcntl.h
+++ b/include/uapi/asm-generic/fcntl.h
@@ -84,6 +84,20 @@
#define O_PATH 010000000
#endif

+#ifndef O_DENYREAD
+#define O_DENYREAD 020000000 /* Do not permit read access */
+#endif
+#ifndef O_DENYWRITE
+#define O_DENYWRITE 040000000 /* Do not permit write access */
+#endif
+/* FMODE_NONOTIFY 0100000000 */
+#ifndef O_DENYDELETE
+#define O_DENYDELETE 0200000000 /* Do not permit delete or rename */
+#endif
+#ifndef O_DENYMAND
+#define O_DENYMAND 0400000000 /* Enable O_DENY flags checks */
+#endif
+
#ifndef O_NDELAY
#define O_NDELAY O_NONBLOCK
#endif
--
1.8.1.1


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