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    Subject[PATCH 3/6] vfs: O_* bit numbers uniqueness check
    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.

    v4: use the nice hweight_long() (suggested by Jamie)
    split O_SYNC to (__O_SYNC | O_DSYNC) (suggested by Andreas)
    take away the FMODE_* and O_RANDOM bits
    v3: change to BUILD_BUG_ON() (suggested by Roland)

    CC: David Miller <davem@davemloft.net>
    CC: Stephen Rothwell <sfr@canb.auug.org.au>
    CC: Al Viro <viro@zeniv.linux.org.uk>
    CC: Christoph Hellwig <hch@infradead.org>
    CC: Eric Paris <eparis@redhat.com>
    CC: Roland Dreier <rdreier@cisco.com>
    CC: Jamie Lokier <jamie@shareable.org>
    CC: Andreas Schwab <schwab@linux-m68k.org>
    Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    ---
    fs/fcntl.c | 14 ++++++++++++--
    include/asm-generic/fcntl.h | 2 ++
    2 files changed, 14 insertions(+), 2 deletions(-)

    --- linux.orig/fs/fcntl.c 2010-01-09 11:02:57.000000000 +0800
    +++ linux/fs/fcntl.c 2010-01-09 21:36:16.000000000 +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 */
    + BUILD_BUG_ON(17 != hweight_long(
    + 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.orig/include/asm-generic/fcntl.h 2010-01-09 11:02:57.000000000 +0800
    +++ linux/include/asm-generic/fcntl.h 2010-01-09 12:23:17.000000000 +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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