Re: [PATCH v3 3/3] fanotify: add API to attach/detach super block mark

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On Fri, Aug 31, 2018 at 5:05 PM Jan Kara <jack@xxxxxxx> wrote:
>
> On Thu 30-08-18 18:15:51, Amir Goldstein wrote:
> > Add another mark type flag FAN_MARK_FILESYSTEM for add/remove/flush
> > of super block mark type.
> >
> > A super block watch gets all events on the filesystem, regardless of
> > the mount from which the mark was added, unless an ignore mask exists
> > on either the inode or the mount where the event was generated.
> >
> > Only one of FAN_MARK_MOUNT and FAN_MARK_FILESYSTEM mark type flags
> > may be provided to fanotify_mark() or no mark type flag for inode mark.
> >
> > Cc: <linux-api@xxxxxxxxxxxxxxx>
> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
>
> Just one nit below, otherwise the patch look good to me.
>
> > diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
> > index 74247917de04..7345b9a57f66 100644
> > --- a/include/uapi/linux/fanotify.h
> > +++ b/include/uapi/linux/fanotify.h
> > @@ -43,6 +43,7 @@
> >                                FAN_UNLIMITED_MARKS)
> >
> >  /* flags used for fanotify_modify_mark() */
> > +#define FAN_MARK_INODE               0x00000000
> >  #define FAN_MARK_ADD         0x00000001
> >  #define FAN_MARK_REMOVE              0x00000002
> >  #define FAN_MARK_DONT_FOLLOW 0x00000004
> > @@ -51,6 +52,7 @@
> >  #define FAN_MARK_IGNORED_MASK        0x00000020
> >  #define FAN_MARK_IGNORED_SURV_MODIFY 0x00000040
> >  #define FAN_MARK_FLUSH               0x00000080
> > +#define FAN_MARK_FILESYSTEM  0x00000100
> >
> >  #define FAN_ALL_MARK_FLAGS   (FAN_MARK_ADD |\
> >                                FAN_MARK_REMOVE |\
> > @@ -59,7 +61,10 @@
> >                                FAN_MARK_MOUNT |\
> >                                FAN_MARK_IGNORED_MASK |\
> >                                FAN_MARK_IGNORED_SURV_MODIFY |\
> > -                              FAN_MARK_FLUSH)
> > +                              FAN_MARK_FLUSH|\
> > +                              FAN_MARK_FILESYSTEM)
> > +
> > +#define FAN_ALL_MARK_TYPE_FLAGS (FAN_MARK_MOUNT | FAN_MARK_FILESYSTEM)
> >
> >  /*
> >   * All of the events - we build the list by hand so that we can add flags in
>
> So for completeness I'd add FAN_MARK_INODE to FAN_ALL_MARK_FLAGS and
> FAN_ALL_MARK_TYPE_FLAGS. I know it doesn't change the actual value but
> logically it belongs there when you defined it...
>

Ok.

> Also one more thing to consider: Different mark types cannot be combined.
> So it could save some bits in 'flags' in future if we had something like
> FAN_MARK_TYPE_MASK and (flags & FAN_MARK_TYPE_MASK) would enumerate
> different mark types - 0 for inode mark, FAN_MARK_MOUNT for mount mark,
> FAN_MARK_FILESYSTEM for superblock mark etc. Again, currently there's no
> practical difference in the values, just the names and tests for validity
> would be slightly different.
>

So do you prefer that I replace the test (mark_type &&
!is_power_of_2(mark_type))
with a switch cases statement for supported types?
Makes sense.

Shall I go as far as:
#define FAN_MARK_TYPE_BIT1      0x00000010
#define FAN_MARK_TYPE_BIT2      0x00000100
#define FAN_MARK_TYPE_MASK (FAN_MARK_TYPE_BIT1 | FAN_MARK_TYPE_BIT2)

/* mark type can be a combination of mark type bits */
#define FAN_MARK_INODE          0
#define FAN_MARK_MOUNT          FAN_MARK_TYPE_BIT1
#define FAN_MARK_FILESYSTEM     FAN_MARK_TYPE_BIT2


Thanks,
Amir.



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