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Tue, 28 Apr 2020 14:58:20 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.58]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2E7F05C220; Tue, 28 Apr 2020 14:58:07 +0000 (UTC) Date: Tue, 28 Apr 2020 15:58:04 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Stefan Hajnoczi Subject: Re: [PATCH] virtiofsd: Show submounts Message-ID: <20200428145804.GC1374620@redhat.com> References: <20200424133516.73077-1-mreitz@redhat.com> <20200427175902.GM2923@work-vm> <20200428145143.GB107541@stefanha-x1.localdomain> MIME-Version: 1.0 In-Reply-To: <20200428145143.GB107541@stefanha-x1.localdomain> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/28 04:11:46 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: virtio-fs@redhat.com, Max Reitz , "Dr. David Alan Gilbert" , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Apr 28, 2020 at 03:51:43PM +0100, Stefan Hajnoczi wrote: > On Mon, Apr 27, 2020 at 06:59:02PM +0100, Dr. David Alan Gilbert wrote: > > * Max Reitz (mreitz@redhat.com) wrote: > > > Currently, setup_mounts() bind-mounts the shared directory without > > > MS_REC. This makes all submounts disappear. > > >=20 > > > Pass MS_REC so that the guest can see submounts again. > >=20 > > Thanks! > >=20 > > > Fixes: 3ca8a2b1c83eb185c232a4e87abbb65495263756 > >=20 > > Should this actually be 5baa3b8e95064c2434bd9e2f312edd5e9ae275dc ? > >=20 > > > Signed-off-by: Max Reitz > > > --- > > > tools/virtiofsd/passthrough_ll.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > >=20 > > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passt= hrough_ll.c > > > index 4c35c95b25..9d7f863e66 100644 > > > --- a/tools/virtiofsd/passthrough_ll.c > > > +++ b/tools/virtiofsd/passthrough_ll.c > > > @@ -2643,7 +2643,7 @@ static void setup_mounts(const char *source) > > > int oldroot; > > > int newroot; > > > =20 > > > - if (mount(source, source, NULL, MS_BIND, NULL) < 0) { > > > + if (mount(source, source, NULL, MS_BIND | MS_REC, NULL) < 0) { > > > fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", sourc= e, source); > > > exit(1); > > > } > >=20 > > Do we want MS_SLAVE to pick up future mounts that might happenf rom the > > host? >=20 > There are two separate concepts: >=20 > 1. Mount namespaces. The virtiofsd process is sandboxed and lives in > its own mount namespace. Therefore it does not share the mounts that > the rest of the host system sees. >=20 > 2. Propagation type. This is related to bind mounts so that mount > operations that happen in one bind-mounted location can also appear > in other bind-mounted locations. >=20 > Since virtiofsd is in a separate mount namespace, does the propagation > type even have any effect? Yes, propagation should work across mount namespaces if you get the mount flags right. You can try it out using unshare + mount commands to debug different scenarios. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|