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SubjectRe: [PATCH] vfs: renumber FMODE_NONOTIFY and add to uniqueness check
On 21.11.2014 10:41, David Drysdale wrote:
> Although FMODE_NONOTIFY is only used internally in the kernel it is in
> the same numbering space as the other O_* flags, as indicated by the
> comment at the top of include/uapi/asm-generic/fcntl.h (and its use
> in fs/notify/fanotify/fanotify_user.c). However, its current value
> clashes with the value of O_PATH on sparc, so renumber it to avoid
> the clash.
>
> All of this has happened before (12ed2e36c98aec6c4155, "fanotify:
> FMODE_NONOTIFY and __O_SYNC in sparc conflict"),

vfs: add nonconflicting values for O_PATH
5229645bdc35f1cc43eb8b25b6993c8fa58b4b43
unfortunately introduced a new conflict.

> and all of this
> will happen again -- so update the uniqueness check in fcntl_init()
> to include __FMODE_NONOTIFY.


>
> Signed-off-by: David Drysdale <drysdale@google.com>
> ---
> fs/fcntl.c | 5 +++--
> include/linux/fs.h | 4 ++--
> include/uapi/asm-generic/fcntl.h | 2 +-
> 3 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 99d440a4a6ba..ee85cd4e136a 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -740,14 +740,15 @@ 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(20 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
> + BUILD_BUG_ON(21 - 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 | __O_TMPFILE
> + __FMODE_EXEC | O_PATH | __O_TMPFILE |
> + __FMODE_NONOTIFY
> ));
>
> fasync_cache = kmem_cache_create("fasync_cache",
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 9ab779e8a63c..fd8611d423a0 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -80,7 +80,7 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
>
> /*
> * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond
> - * to O_WRONLY and O_RDWR via the strange trick in __dentry_open()
> + * to O_WRONLY and O_RDWR via the strange trick in OPEN_FMODE() below.

Please, put this change into a separate patch.
It seems unrelated to the definition of __FMODE_NONOTIFY.

> */
>
> /* file is open for reading */
> @@ -134,7 +134,7 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
> #define FMODE_CAN_WRITE ((__force fmode_t)0x40000)
>
> /* File was opened by fanotify and shouldn't generate fanotify events */
> -#define FMODE_NONOTIFY ((__force fmode_t)0x1000000)
> +#define FMODE_NONOTIFY ((__force fmode_t)0x4000000)

The cause of the pain is
arch/sparc/include/uapi/asm/fcntl.h:37:
#define O_PATH 0x1000000
We cannot change that definition due to the need for backwards
compatibility.

>
> /*
> * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
> diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
> index 7543b3e51331..e063effe0cc1 100644
> --- a/include/uapi/asm-generic/fcntl.h
> +++ b/include/uapi/asm-generic/fcntl.h
> @@ -5,7 +5,7 @@
>
> /*
> * FMODE_EXEC is 0x20
> - * FMODE_NONOTIFY is 0x1000000
> + * FMODE_NONOTIFY is 0x4000000
> * These cannot be used by userspace O_* until internal and external open
> * flags are split.
> * -Eric Paris
>

The patch is applicable to 3.18.0-rc4.

I CC Jan as he has done a lot of the recent file notification development.

Best regards

Heinrich Schuchardt


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