From: Ian Kent <raven@themaw.net>
To: Miklos Szeredi <miklos@szeredi.hu>, David Howells <dhowells@redhat.com>
Cc: viro@zeniv.linux.org.uk, torvalds@linux-foundation.org,
mszeredi@redhat.com, christian@brauner.io, jannh@google.com,
darrick.wong@oracle.com, kzak@redhat.com, jlayton@redhat.com,
linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount [ver #21]
Date: Tue, 04 Aug 2020 20:32:04 +0800 [thread overview]
Message-ID: <3341383b655b39697b4dcdb9f64c5f3bc46a6ac4.camel@themaw.net> (raw)
In-Reply-To: <20200804104108.GC32719@miu.piliscsaba.redhat.com>
On Tue, 2020-08-04 at 12:41 +0200, Miklos Szeredi wrote:
> On Mon, Aug 03, 2020 at 02:37:16PM +0100, David Howells wrote:
> > Add a uniquifier ID to struct mount that is effectively unique over
> > the
> > kernel lifetime to deal around mnt_id values being reused. This
> > can then
> > be exported through fsinfo() to allow detection of replacement
> > mounts that
> > happen to end up with the same mount ID.
> >
> > The normal mount handle is still used for referring to a particular
> > mount.
> >
> > The mount notification is then changed to convey these unique mount
> > IDs
> > rather than the mount handle.
> >
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > ---
> >
> > fs/mount.h | 3 +++
> > fs/mount_notify.c | 4 ++--
> > fs/namespace.c | 3 +++
> > 3 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/mount.h b/fs/mount.h
> > index 85456a5f5a3a..1037781be055 100644
> > --- a/fs/mount.h
> > +++ b/fs/mount.h
> > @@ -79,6 +79,9 @@ struct mount {
> > int mnt_expiry_mark; /* true if marked for
> > expiry */
> > struct hlist_head mnt_pins;
> > struct hlist_head mnt_stuck_children;
> > +#ifdef CONFIG_FSINFO
> > + u64 mnt_unique_id; /* ID unique over lifetime of
> > kernel */
> > +#endif
>
> Not sure if it's worth making conditional.
>
> > #ifdef CONFIG_MOUNT_NOTIFICATIONS
> > struct watch_list *mnt_watchers; /* Watches on dentries within
> > this mount */
> > #endif
> > diff --git a/fs/mount_notify.c b/fs/mount_notify.c
> > index 44f570e4cebe..d8ba66ed5f77 100644
> > --- a/fs/mount_notify.c
> > +++ b/fs/mount_notify.c
> > @@ -90,7 +90,7 @@ void notify_mount(struct mount *trigger,
> > n.watch.type = WATCH_TYPE_MOUNT_NOTIFY;
> > n.watch.subtype = subtype;
> > n.watch.info = info_flags | watch_sizeof(n);
> > - n.triggered_on = trigger->mnt_id;
> > + n.triggered_on = trigger->mnt_unique_id;
> >
> > switch (subtype) {
> > case NOTIFY_MOUNT_EXPIRY:
> > @@ -102,7 +102,7 @@ void notify_mount(struct mount *trigger,
> > case NOTIFY_MOUNT_UNMOUNT:
> > case NOTIFY_MOUNT_MOVE_FROM:
> > case NOTIFY_MOUNT_MOVE_TO:
> > - n.auxiliary_mount = aux->mnt_id;
> > + n.auxiliary_mount = aux->mnt_unique_id;
>
> Hmm, so we now have two ID's:
>
> - one can be used to look up the mount
> - one is guaranteed to be unique
>
> With this change the mount cannot be looked up with
> FSINFO_FLAGS_QUERY_MOUNT,
> right?
>
> Should we be merging the two ID's into a single one which has both
> properties?
I'd been thinking we would probably need to change to 64 bit ids
for a while now and I thought that was what was going to happen.
We'll need to change libmount and current code but better early
on than later.
Ian
>
> > break;
> >
> > default:
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index b2b9920ffd3c..1db8a64cd76f 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -115,6 +115,9 @@ static int mnt_alloc_id(struct mount *mnt)
> > if (res < 0)
> > return res;
> > mnt->mnt_id = res;
> > +#ifdef CONFIG_FSINFO
> > + mnt->mnt_unique_id = atomic64_inc_return(&vfs_unique_counter);
> > +#endif
> > return 0;
> > }
> >
> >
> >
next prev parent reply other threads:[~2020-08-04 12:33 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 13:36 [PATCH 00/18] VFS: Filesystem information [ver #21] David Howells
2020-08-03 13:36 ` [PATCH 01/18] fsinfo: Introduce a non-repeating system-unique superblock ID " David Howells
2020-08-04 9:34 ` Miklos Szeredi
2020-08-03 13:36 ` [PATCH 02/18] fsinfo: Add fsinfo() syscall to query filesystem information " David Howells
2020-08-04 10:16 ` Miklos Szeredi
2020-08-04 11:34 ` David Howells
2020-08-27 11:27 ` Michael Kerrisk (man-pages)
2020-08-03 13:36 ` [PATCH 03/18] fsinfo: Provide a bitmap of the features a filesystem supports " David Howells
2020-08-03 13:37 ` [PATCH 04/18] fsinfo: Allow retrieval of superblock devname, options and stats " David Howells
2020-08-03 13:37 ` [PATCH 05/18] fsinfo: Allow fsinfo() to look up a mount object by ID " David Howells
2020-08-04 10:33 ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 06/18] fsinfo: Add a uniquifier ID to struct mount " David Howells
2020-08-04 10:41 ` Miklos Szeredi
2020-08-04 12:32 ` Ian Kent [this message]
2020-08-05 14:13 ` David Howells
2020-08-05 14:46 ` Miklos Szeredi
2020-08-05 15:30 ` David Howells
2020-08-05 19:33 ` Matthew Wilcox
2020-08-06 5:43 ` Ian Kent
2020-08-03 13:37 ` [PATCH 07/18] fsinfo: Allow mount information to be queried " David Howells
2020-08-03 13:37 ` [PATCH 08/18] fsinfo: Allow mount topology and propagation info to be retrieved " David Howells
2020-08-04 13:38 ` Miklos Szeredi
2020-08-05 15:37 ` David Howells
2020-08-05 17:19 ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 09/18] watch_queue: Mount event counters " David Howells
2020-08-03 13:37 ` [PATCH 10/18] fsinfo: Provide notification overrun handling support " David Howells
2020-08-04 13:56 ` Miklos Szeredi
2020-08-05 2:05 ` Ian Kent
2020-08-05 2:46 ` Ian Kent
2020-08-05 7:45 ` Miklos Szeredi
2020-08-05 11:23 ` Ian Kent
2020-08-05 11:27 ` Miklos Szeredi
2020-08-06 1:47 ` Ian Kent
2020-08-05 16:06 ` David Howells
2020-08-05 17:26 ` Miklos Szeredi
2020-08-03 13:37 ` [PATCH 11/18] fsinfo: sample: Mount listing program " David Howells
2020-08-03 13:38 ` [PATCH 12/18] fsinfo: Add API documentation " David Howells
2020-08-03 13:38 ` [PATCH 13/18] fsinfo: Add support for AFS " David Howells
2020-08-03 13:38 ` [PATCH 14/18] fsinfo: Add support to ext4 " David Howells
2020-08-03 13:38 ` [PATCH 15/18] fsinfo: Add an attribute that lists all the visible mounts in a namespace " David Howells
2020-08-04 14:05 ` Miklos Szeredi
2020-08-05 0:59 ` Ian Kent
2020-08-05 16:44 ` David Howells
2020-08-03 13:38 ` [PATCH 16/18] errseq: add a new errseq_scrape function " David Howells
2020-08-03 13:38 ` [PATCH 17/18] vfs: allow fsinfo to fetch the current state of s_wb_err " David Howells
2020-08-03 13:39 ` [PATCH 18/18] samples: add error state information to test-fsinfo.c " David Howells
2020-08-04 15:39 ` [PATCH 00/18] VFS: Filesystem information " James Bottomley
2020-08-04 19:18 ` Miklos Szeredi
2020-08-05 17:13 ` David Howells
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