On Wed, Jan 06, 2010 at 03:08:08PM +0800, Roland Dreier wrote:
>
> > + /* please add new bits here to ensure allocation uniqueness */
> > + BUG_ON(20 != hweight32(
> > + O_RDONLY | O_WRONLY | O_RDWR |
>
> I wonder if there's a way to make this BUILD_BUG_ON(), so the problem is
> caught at compile time (a change like adding an O_ flag is often compile
> tested only for obscure archs). One could create a compile-time
> macro-ized version of hweight32() and use that, I guess, although I'm
> not sure it's worth the ugliness.
Yeah, I chose the boot time check because of hweight32()..
> Failing that maybe this should be WARN_ON()? I'd be annoyed if my arch
> wouldn't boot because some strange new O_ flag happened to collide.
Good suggestion! Here is the updated patch.
Andrew, this patch relies on the newly introduced O_RANDOM and Eric's
FMODE_NONOTIFY.
Thanks,
Fengguang
---
fs: O_* bit numbers uniqueness check
The O_* bit numbers are defined in 20+ arch/*, and hence can silently
overlap. Add a boot time check to ensure the uniqueness as suggested
by David Miller.
v2: change to WARN_ON() as suggested by Roland
CC: David Miller <davem@xxxxxxxxxxxxx>
CC: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Christoph Hellwig <hch@xxxxxxxxxxxxx>
CC: Eric Paris <eparis@xxxxxxxxxx>
CC: Roland Dreier <rdreier@xxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/fcntl.c | 14 ++++++++++++--
include/asm-generic/fcntl.h | 2 ++
2 files changed, 14 insertions(+), 2 deletions(-)
--- linux.orig/fs/fcntl.c 2010-01-06 14:41:26.000000000 +0800
+++ linux/fs/fcntl.c 2010-01-06 15:15:11.000000000 +0800
@@ -709,11 +709,21 @@ 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 */
+ WARN_ON(20 != hweight32(
+ O_RDONLY | O_WRONLY | O_RDWR |
+ O_CREAT | O_EXCL | O_NOCTTY |
+ O_TRUNC | O_APPEND | O_NONBLOCK |
+ O_SYNC | FASYNC | O_DIRECT |
+ O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW |
+ O_NOATIME | O_CLOEXEC | O_RANDOM |
+ FMODE_EXEC | FMODE_NONOTIFY));
+
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.orig/include/asm-generic/fcntl.h 2010-01-06 14:45:34.000000000 +0800
+++ linux/include/asm-generic/fcntl.h 2010-01-06 14:50:57.000000000 +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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