[PATCH 8/9 linux-next] fanotify: clarify mark type extraction

[PATCH 8/9 linux-next] fanotify: clarify mark type extraction

[Fabian Frederick]

mark type is resolved from flags but is not itself bitwise.
That means user could send a combination and never note
only one value was taken in consideration. This patch clarifies
that fact in bit definitions.

Thanks to Amir for explanations.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
 include/uapi/linux/fanotify.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index a88c7c6d0692..675bf6bbbe50 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -71,7 +71,12 @@
 #define FAN_MARK_FLUSH		0x00000080
 /* FAN_MARK_FILESYSTEM is	0x00000100 */
 
-/* These are NOT bitwise flags.  Both bits can be used togther.  */
+/*
+ * These are NOT bitwise flags.  Both bits can be used together.
+ * IOW if someone does FAN_MARK_INODE | FAN_MARK_FILESYSTEM
+ * it will be considered FAN_MARK_FILESYSTEM and user won't be
+ * notified.
+ */
 #define FAN_MARK_INODE		0x00000000
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_FILESYSTEM	0x00000100
-- 
2.26.2

Re: [PATCH 8/9 linux-next] fanotify: clarify mark type extraction

[Amir Goldstein]

On Mon, May 11, 2020 at 9:02 PM Fabian Frederick <fabf@skynet.be> wrote:
>
> mark type is resolved from flags but is not itself bitwise.
> That means user could send a combination and never note
> only one value was taken in consideration. This patch clarifies
> that fact in bit definitions.
>
> Thanks to Amir for explanations.
>
> Signed-off-by: Fabian Frederick <fabf@skynet.be>
> ---
>  include/uapi/linux/fanotify.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
> index a88c7c6d0692..675bf6bbbe50 100644
> --- a/include/uapi/linux/fanotify.h
> +++ b/include/uapi/linux/fanotify.h
> @@ -71,7 +71,12 @@
>  #define FAN_MARK_FLUSH         0x00000080
>  /* FAN_MARK_FILESYSTEM is      0x00000100 */
>
> -/* These are NOT bitwise flags.  Both bits can be used togther.  */
> +/*
> + * These are NOT bitwise flags.  Both bits can be used together.
> + * IOW if someone does FAN_MARK_INODE | FAN_MARK_FILESYSTEM
> + * it will be considered FAN_MARK_FILESYSTEM and user won't be
> + * notified.

Sorry, I don't find that those added lines add information.
They are stating something obvious.
Especially, in uapi file, I rather not say anything at all then say
confusing things.

Thanks,
Amir.

> + */
>  #define FAN_MARK_INODE         0x00000000
>  #define FAN_MARK_MOUNT         0x00000010
>  #define FAN_MARK_FILESYSTEM    0x00000100
> --
> 2.26.2
>