linux-kernel - Re: Question: Why is there no notification when a file is opened using filp

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Message-ID: <CAOQ4uxgvodepq2ZhmGEpkZYj017tH_pk2AgV=pUhWiONnxOQjw@mail.gmail.com>
Date:   Tue, 8 Sep 2020 16:18:29 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Xiaoming Ni <nixiaoming@...wei.com>
Cc:     Jan Kara <jack@...e.cz>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        wangle6@...wei.com
Subject: Re: Question: Why is there no notification when a file is opened
 using filp_open()?

On Tue, Sep 8, 2020 at 3:53 PM Xiaoming Ni <nixiaoming@...wei.com> wrote:
>
> On 2020/9/8 18:06, Amir Goldstein wrote:
> > On Tue, Sep 8, 2020 at 11:02 AM Xiaoming Ni <nixiaoming@...wei.com> wrote:
> >>
> >> The file opening action on the system may be from user-mode sys_open()
> >> or kernel-mode filp_open().
> >> Currently, fsnotify_open() is invoked in do_sys_openat2().
> >> But filp_open() is not notified. Why? Is this an omission?
> >>
> >> Do we need to call fsnotify_open() in filp_open() or  do_filp_open() to
> >> ensure that both user-mode and kernel-mode file opening operations can
> >> be notified?
> >>
> >
> > Do you have a specific use case of kernel filp_open() in mind?
> >
>
> For example, in fs/coredump.c, do_coredump() calls filp_open() to
> generate core files.
> In this scenario, the fsnotify_open() notification is missing.
>

I am not convinced that we should generate an event.
You will have to explain in what is the real world use case that requires this
event to be generated.

Thanks,
Amir.