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From: Wu Fengguang on 15 Mar 2010 21:20
The O_* bit numbers are defined in 20+ arch/*, and can silently overlap.
Add a compile time check to ensure the uniqueness as suggested by David
Miller.

Cc: David Miller <davem(a)davemloft.net>
Cc: Stephen Rothwell <sfr(a)canb.auug.org.au>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch(a)infradead.org>
Cc: Eric Paris <eparis(a)redhat.com>
Cc: Roland Dreier <rdreier(a)cisco.com>
Cc: Jamie Lokier <jamie(a)shareable.org>
Cc: Andreas Schwab <schwab(a)linux-m68k.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Wu Fengguang <fengguang.wu(a)intel.com>
---

fs/fcntl.c | 14 ++++++++++++--
include/asm-generic/fcntl.h | 2 ++
2 files changed, 14 insertions(+), 2 deletions(-)

--- linux-mm.orig/fs/fcntl.c 2010-03-11 13:52:59.000000000 +0800
+++ linux-mm/fs/fcntl.c 2010-03-16 09:07:43.000000000 +0800
@@ -739,11 +739,21 @@ void kill_fasync(struct fasync_struct **
}
EXPORT_SYMBOL(kill_fasync);

-static int __init fasync_init(void)
+static int __init fcntl_init(void)
{
+ /* please add new bits here to ensure allocation uniqueness */
+ BUILD_BUG_ON(17 != 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
+ ));
+
fasync_cache = kmem_cache_create("fasync_cache",
sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
return 0;
}

-module_init(fasync_init)
+module_init(fcntl_init)
--- linux-mm.orig/include/asm-generic/fcntl.h 2010-03-11 13:52:59.000000000 +0800
+++ linux-mm/include/asm-generic/fcntl.h 2010-03-12 21:26:41.000000000 +0800
@@ -4,6 +4,8 @@
#include <linux/types.h>

/*
+ * When introducing new O_* bits, please check its uniqueness in fcntl_init().
+ *
* FMODE_EXEC is 0x20
* FMODE_NONOTIFY is 0x1000000
* These cannot be used by userspace O_* until internal and external open


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