linux-ext4 - Re: [PATCH v8 02/19] fsnotify: opt-in for permission events at file open time

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Message-ID: <CAOQ4uxh-LTvBg93GLtdVp7ixwJLCy+Q1GgSijAs0iZ4k++AuCQ@mail.gmail.com>
Date: Thu, 21 Nov 2024 12:32:34 +0100
From: Amir Goldstein <amir73il@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: Christian Brauner <brauner@...nel.org>, Josef Bacik <josef@...icpanda.com>, kernel-team@...com, 
	linux-fsdevel@...r.kernel.org, torvalds@...ux-foundation.org, 
	viro@...iv.linux.org.uk, linux-xfs@...r.kernel.org, 
	linux-btrfs@...r.kernel.org, linux-mm@...ck.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH v8 02/19] fsnotify: opt-in for permission events at file
 open time

On Thu, Nov 21, 2024 at 12:16 PM Jan Kara <jack@...e.cz> wrote:
>
> On Thu 21-11-24 12:04:23, Amir Goldstein wrote:
> > On Thu, Nov 21, 2024 at 11:09 AM Christian Brauner <brauner@...nel.org> wrote:
> > >
> > > > It is not that I object to "two bit constants". FMODE_FSNOTIFY_MASK is a
> > > > two-bit constant and a good one. But the name clearly suggests it is not a
> > > > single bit constant. When you have all FMODE_FOO and FMODE_BAR things
> > > > single bit except for FMODE_BAZ which is multi-bit, then this is IMHO a
> > > > recipe for problems and I rather prefer explicitely spelling the
> > > > combination out as FMODE_NONOTIFY | FMODE_NONOTIFY_PERM in the few places
> > > > that need this instead of hiding it behind some other name.
> > >
> > > Very much agreed!
> >
> > Yes, I agree as well.
> > What I meant is that the code that does
> >     return FMODE_NONOTIFY | FMODE_NONOTIFY_PERM;
> >
> > is going to be unclear to the future code reviewer unless there is
> > a comment above explaining that this is a special flag combination
> > to specify "suppress only pre-content events".
>
> So this combination is used in file_set_fsnotify_mode() only (three
> occurences) and there I have:
>
>         /*
>          * If there are permission event watchers but no pre-content event
>          * watchers, set FMODE_NONOTIFY | FMODE_NONOTIFY_PERM to indicate that.
>          */
>
> at the first occurence. So hopefully that's enough of an explanation.
>

Yes, that's the comment that I did not see, but assumed it was there ;)
which I wrongly expressed as "I wonder how you annotated".

Thanks,
Amir.