From: Dave Chinner <david@fromorbit.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Jan Kara <jack@suse.cz>,
Christian Brauner <christian.brauner@ubuntu.com>,
linux-xfs <linux-xfs@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
"J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: [PATCH] xfs: use a unique and persistent value for f_fsid
Date: Fri, 26 Mar 2021 10:03:12 +1100 [thread overview]
Message-ID: <20210325230312.GN63242@dread.disaster.area> (raw)
In-Reply-To: <CAOQ4uxgOi9hxDaL7Rk8OU3O-S+YuvDZPtpN7PggXfL=COyrc0Q@mail.gmail.com>
On Wed, Mar 24, 2021 at 11:18:36AM +0200, Amir Goldstein wrote:
> On Wed, Mar 24, 2021 at 9:43 AM Christoph Hellwig <hch@infradead.org> wrote:
> >
> > On Wed, Mar 24, 2021 at 08:53:25AM +0200, Amir Goldstein wrote:
> > > > This also means that userspace can be entirely filesystem agnostic
> > > > and it doesn't need to rely on parsing proc files to translate
> > > > ephemeral mount IDs to paths, statvfs() and hoping that f_fsid is
> > > > stable enough that it doesn't get the destination wrong. It also
> > > > means that fanotify UAPI probably no longer needs to supply a
> > > > f_fsid with the filehandle because it is built into the
> > > > filehandle....
> > > >
> > >
> > > That is one option. Let's call it the "bullet proof" option.
> > >
> > > Another option, let's call it the "pragmatic" options, is that you accept
> > > that my patch shouldn't break anything and agree to apply it.
> >
> > Your patch may very well break something. Most Linux file systems do
> > store the dev_t in the fsid and userspace may for whatever silly
> > reasons depend on it.
> >
>
> I acknowledge that.
> I do not claim that my change carries zero risk of breakage.
> However, if such userspace dependency exists, it would break on ext4,
> btrfs, ocsf2, ceph and many more fs, so it would have to be a
> dependency that is tightly coupled with a specific fs.
> The probability of that is rather low IMO.
>
> I propose an opt-in mount option "-o fixed_fsid" for this behavior to make
> everyone sleep better.
Layering hacks on top of hacks to avoid fixing the fanotify UAPI
limitations isn't a very palatable option. Especially those that
require adding mount options we'll have to support forever more...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2021-03-25 23:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 17:11 [PATCH] xfs: use a unique and persistent value for f_fsid Amir Goldstein
2021-03-22 23:03 ` Dave Chinner
2021-03-23 4:50 ` Amir Goldstein
2021-03-23 6:35 ` Darrick J. Wong
2021-03-23 6:44 ` Amir Goldstein
2021-03-23 7:26 ` Dave Chinner
2021-03-23 9:35 ` Amir Goldstein
2021-03-24 0:54 ` Dave Chinner
2021-03-24 6:53 ` Amir Goldstein
2021-03-24 7:43 ` Christoph Hellwig
2021-03-24 9:18 ` Amir Goldstein
2021-03-25 23:03 ` Dave Chinner [this message]
2021-03-25 22:53 ` Dave Chinner
2021-03-26 6:04 ` Amir Goldstein
2021-03-26 22:34 ` Theodore Ts'o
2021-03-27 9:14 ` Amir Goldstein
2021-03-26 19:15 ` J. Bruce Fields
2021-03-27 9:06 ` Amir Goldstein
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