[PATCH 1/2] libmount: dont ignore autofs mounts by default

[PATCH 1/2] libmount: dont ignore autofs mounts by default

[Ian Kent]

Making libmount ingore autofs mounts by default can be a problem for
systemd, I remember now what the problem was.

autofs multi-mounts can be nested (and often are, think of a tree of
NFS exports) where there are autofs file system mounts within NFS
mounts and together with autofs mount triggers.

In this case systemd needs to see all the mounts at shutdown when it
is umounting the tree of mounts. We don't want to have to rely on
modifications having been made to systemd for this to work properly
so we can't make this the default behaviour in libmount.

Fixes: 22147e08c987 (libmount: use autofs mount hint to ignore autofs mount entries)
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: John Westerdale <jwesterd@redhat.com>
Cc: Frank Hertz <fhirtz@redhat.com>
Cc: Frank Sorenson <fsorenso@redhat.com>
---
 libmount/src/context.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libmount/src/context.c b/libmount/src/context.c
index 8db6b6950..2df4716a7 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -75,7 +75,7 @@ struct libmnt_context *mnt_new_context(void)
 	/* if we're really root and aren't running setuid */
 	cxt->restricted = (uid_t) 0 == ruid && ruid == euid ? 0 : 1;
 
-	cxt->noautofs = 1;
+	cxt->noautofs = 0;
 
 	DBG(CXT, ul_debugobj(cxt, "----> allocate %s",
 				cxt->restricted ? "[RESTRICTED]" : ""));
@@ -164,7 +164,7 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	cxt->helper = NULL;
 	cxt->mountdata = NULL;
 	cxt->flags = MNT_FL_DEFAULT;
-	cxt->noautofs = 1;
+	cxt->noautofs = 0;
 	cxt->has_selinux_opt = 0;
 
 	cxt->map_linux = mnt_get_builtin_optmap(MNT_LINUX_MAP);

[PATCH 2/2] mount: ignore autofs entries in mount listing

[Ian Kent]

Since we can't enable use of ignoring autofs mounts that have the
"ignore" option present by default (systemd could get confused) it's
necessary to enable it for individual applications.

The mount utility is one applcation we need it for so enable it.

Signed-off-by: Ian Kent <raven@themaw.net>
Cc: John Westerdale <jwesterd@redhat.com>
Cc: Frank Hertz <fhirtz@redhat.com>
Cc: Frank Sorenson <fsorenso@redhat.com>
---
 sys-utils/mount.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys-utils/mount.c b/sys-utils/mount.c
index 6590272c7..dba6fcae9 100644
--- a/sys-utils/mount.c
+++ b/sys-utils/mount.c
@@ -124,6 +124,8 @@ static void print_all(struct libmnt_context *cxt, char *pattern, int show_label)
 	struct libmnt_fs *fs;
 	struct libmnt_cache *cache = NULL;
 
+	mnt_context_enable_noautofs(cxt, 1);
+
 	if (mnt_context_get_mtab(cxt, &tb))
 		err(MNT_EX_SYSERR, _("failed to read mtab"));
 

Re: [PATCH 1/2] libmount: dont ignore autofs mounts by default

[Karel Zak]

On Mon, Mar 13, 2023 at 09:42:56AM +0800, Ian Kent wrote:
> so we can't make this the default behaviour in libmount.

I see ;-) Applied (both patches).

What about findmnt? I think it should follow "ignore" by default too
(if --all no specified).

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: [PATCH 1/2] libmount: dont ignore autofs mounts by default

[Ian Kent]

On 15/3/23 22:32, Karel Zak wrote:
> On Mon, Mar 13, 2023 at 09:42:56AM +0800, Ian Kent wrote:
>> so we can't make this the default behaviour in libmount.
> I see ;-) Applied (both patches).
>
> What about findmnt? I think it should follow "ignore" by default too
> (if --all no specified).

Thanks very much.


I'll have a look at findmnt but the main driver is admin users

struggling with cuter on screen output.


I thought findmnt is more often used in admin scripts where it

may be more sensible to not ignore mounts. Of course not ignoring

the mounts for the --all option might make sense.


Ian

[PATCH 0/2] Add ability to use autofs mount option hint to exclude mount table list entries

[Ian Kent]

Historically autofs mounts were not included in mount table listings.

This is the case in other SysV autofs implementations and was also
the case with Linux autofs until we changed to use the proc file system
for the mount table.

This often leads to considerable clutter for system administrators so
it's necessary to find a way to exclude these entries from mount table
listings without causing problems for sub-systems that may need the
entries to be present.

In other Unix autofs implementations we see this is done by including
a pseudo mount option that's used as a hint by applications that want
to exclude these entries.

There's further discussion of this in the first patch.

I started trying to do this quite a while ago, glibc, automount(8) and
the kernel have been updated to use such a mount option but, for some
reason, when I canme to update util-linux I thought it would cause
problems for systemd. But when I looked at what I had done just recently
I saw that isn't the case so I'm now continuing with this change.

What I've done might not be the prefered way to do this so any comments
are welcome so it can be done the way it fits best with util-linux.

Signed-off-by: Ian Kent <raven@themaw.net>
---

Ian Kent (2):
      libmount: use autofs mount hint to ignore autofs mount entries
      mount: ignore autofs entries in mount listing


 libmount/src/context.c     | 19 +++++++++++++++++++
 libmount/src/libmount.h.in |  2 ++
 libmount/src/libmount.sym  |  3 +++
 libmount/src/mountP.h      |  7 ++++++-
 libmount/src/tab_parse.c   | 33 +++++++++++++++++++++++++++++++++
 sys-utils/mount.c          |  2 ++
 6 files changed, 65 insertions(+), 1 deletion(-)

--
Ian

[PATCH 2/2] mount: ignore autofs entries in mount listing

[Ian Kent]

Use the autofs mount option hint to ignore autofs mount table entries.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 sys-utils/mount.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys-utils/mount.c b/sys-utils/mount.c
index 283998f3b..29fda6b05 100644
--- a/sys-utils/mount.c
+++ b/sys-utils/mount.c
@@ -124,6 +124,8 @@ static void print_all(struct libmnt_context *cxt, char *pattern, int show_label)
 	struct libmnt_fs *fs;
 	struct libmnt_cache *cache = NULL;
 
+	mnt_context_enable_ignore_autofs(cxt);
+
 	if (mnt_context_get_mtab(cxt, &tb))
 		err(MNT_EX_SYSERR, _("failed to read mtab"));