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

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Message-ID: <20241121111644.y63uejriiti4vce5@quack3>
Date: Thu, 21 Nov 2024 12:16:44 +0100
From: Jan Kara <jack@...e.cz>
To: Amir Goldstein <amir73il@...il.com>
Cc: Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	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 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.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR