Re: File monitor problem

[Mo Re Ra <more7.rev@gmail.com>]

On Wed, Dec 4, 2019 at 4:23 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Wed, Dec 4, 2019 at 12:03 PM Mo Re Ra <more7.rev@gmail.com> wrote:
> >
> > Hi,
> >
> > I don`t know if this is the correct place to express my issue or not.
> > I have a big problem. For my project, a Directory Monitor, I`ve
> > researched about dnotify, inotify and fanotify.
> > dnotify is the worst choice.
> > inotify is a good choice but has a problem. It does not work
> > recursively. When you implement this feature by inotify, you would
> > miss immediately events after subdir creation.
> > fanotify is the last choice. It has a big change since Kernel 5.1. But
> > It does not meet my requirement.
> >
> > I need to monitor a directory with CREATE, DELETE, MOVE_TO, MOVE_FROM
> > and CLOSE_WRITE events would be happened in its subdirectories.
> > Filename of the events happened on that (without any miss) is
> > mandatory for me.
> >
> > I`ve searched and found a contribution from @amiril73 which
> > unfortunately has not been merged. Here is the link:
> > https://github.com/amir73il/fsnotify-utils/issues/1
> >
> > I`d really appreciate it If you could resolve this issue.
> >
>
> Hi Mohammad,
>
> Thanks for taking an interest in fanotify.
>
> Can you please elaborate about why filename in events are mandatory
> for your application.
>
> Could your application use the FID in FAN_DELETE_SELF and
> FAN_MOVE_SELF events to act on file deletion/rename instead of filename
> information in FAN_DELETE/FAN_MOVED_xxx events?
>
> Will it help if you could get a FAN_CREATE_SELF event with FID information
> of created file?
>
> Note that it is NOT guarantied that your application will be able to resolve
> those FID to file path, for example if file was already deleted and no open
> handles for this file exist or if file has a hardlink, you may resolve the path
> of that hardlink instead.
>
> Jan,
>
> I remember we discussed the optional FAN_REPORT_FILENAME [1] and
> you had some reservations, but I am not sure how strong they were.
> Please refresh my memory.
>
> Thanks,
> Amir.
>
> [1] https://github.com/amir73il/linux/commit/d3e2fec74f6814cecb91148e6b9984a56132590f



Hi Amir,
Thanks for your attention.

Fanotify project had a big change since Kernel 5.1 but did not meet
some primiry needs.
For example in my application, I`m watching on a specific directory to
sync it (through a socket connection and considering some policies)
with a directory in a remote system which a user working on that. Some
subdirectoires may contain two milions of files or more. I need these
two directoires be synced completely as soon as possible without any
missed notification.
So, I need a syscall with complete set of flags to help to watch on a
directory and all of its subdirectories recuresively without any
missed notification.

Unfortuantely, in current version of Fanotify, the notification just
expresses a change has been occured in a directory but dot not
specifiy which file! I could not iterate over millions of file to
determine which file was that. That would not be helpful.

Inevitably, xxx_SELF would not help me to meets all I need. Just to
clarify, I dont mean xxx_SELF flags are useless. I mean Fanotify is a
good project but the current version of that is not a project which
meets some basic needs.

Thanks,
Mohammad Reza.