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From: Amir Goldstein <amir73il@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC][PATCH] fanotify: introduce filesystem view mark
Date: Thu, 26 Nov 2020 13:50:06 +0200
Message-ID: <CAOQ4uxgtw14=CsYLYniDzrOjWKj3RKqWREW-9NO55Z6JMr8RJw@mail.gmail.com> (raw)
In-Reply-To: <20201126111036.GC422@quack2.suse.cz>

On Thu, Nov 26, 2020 at 1:10 PM Jan Kara <jack@suse.cz> wrote:
>
> On Wed 25-11-20 14:34:16, Amir Goldstein wrote:
> > On Wed, Nov 25, 2020 at 1:01 PM Jan Kara <jack@suse.cz> wrote:
> > > In fact I was considering for a while that we could even make subtree
> > > watches completely unpriviledged - when we walk the dir tree anyway, we
> > > could also check permissions along the way. Due to locking this would be
> > > difficult to do when generating the event but it might be actually doable
> > > if we perform the permission check when reporting the event to userspace.
> > > Just a food for thought...
> >
> > Maybe... but there are some other advantages to restricting to mount.
> >
> > One is that with btrfs subvolumes conn->fsid can actually cache the
> > subvolume's fsid and we could remove the restriction of -EXDEV
> > error of FAN_MARK_FILESYSTEM on subvolume.
>
> I'm not sure I understand this - do you mean we could support
> FAN_MARK_FILESYSTEM_SUBTREE on btrfs subvolumes? I agree with that. I'm

Yes, that's what I meant.

> just not sure how subtree watches are related to general
> FAN_MARK_FILESYSTEM marks on btrfs...
>

I thought that it would solve the ambiguity issue with btrfs fsid
(it differs for objects inside a subvolume), because conn->fsid
of subtree would cache the subvolume's fsid, but if there are both
a filesystem mark and subtree mark on a subvolume, that would
result in ambiguity again, so we are still not out of the woods.

If this hand waving wasn't clear, don't worry about it.
I will think about it some more and document the issue in my next post.

Thanks,
Amir.

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-09 18:00 Amir Goldstein
2020-11-10  5:07 ` Amir Goldstein
2020-11-17  7:09 ` [fanotify] a23a7dc576: unixbench.score -3.7% regression kernel test robot
2020-11-24 13:49 ` [RFC][PATCH] fanotify: introduce filesystem view mark Jan Kara
2020-11-24 14:47   ` Amir Goldstein
2020-11-25 11:01     ` Jan Kara
2020-11-25 12:34       ` Amir Goldstein
2020-11-26 11:10         ` Jan Kara
2020-11-26 11:50           ` Amir Goldstein [this message]
2020-11-26  3:42       ` Amir Goldstein
2020-11-26 11:17         ` Jan Kara
2021-04-28 18:28           ` Amir Goldstein
2021-05-03 16:53             ` Jan Kara
2021-05-03 18:44               ` Amir Goldstein
2021-05-05 12:28                 ` Jan Kara
2021-05-05 14:24                   ` Christian Brauner
2021-05-05 14:42                     ` Amir Goldstein
2021-05-05 14:56                       ` Christian Brauner
2021-05-10 10:13                     ` Jan Kara
2021-05-10 11:37                       ` Amir Goldstein
2021-05-10 14:21                         ` Jan Kara
2021-05-10 15:08                           ` Amir Goldstein
2021-05-10 15:27                             ` Jan Kara
2021-05-12 13:07                             ` Christian Brauner
2021-05-12 13:34                               ` Jan Kara
2021-05-12 16:15                                 ` Christian Brauner
2021-05-12 15:26                         ` Christian Brauner
2021-05-13 10:55                           ` Jan Kara
2021-05-14 13:56                             ` Christian Brauner
2021-05-15 14:28                               ` Amir Goldstein
2021-05-17  9:09                                 ` Jan Kara
2021-05-17 12:45                                   ` Amir Goldstein
2021-05-17 13:07                                     ` Jan Kara
2021-05-18 10:11                                 ` Christian Brauner
2021-05-18 16:02                                   ` Amir Goldstein
2021-05-19  9:31                                     ` Christian Brauner
2021-05-12 16:11                         ` Christian Brauner
2021-05-05 13:25               ` Christian Brauner

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