I am able to workaround this issue by marking the mount as unbinadable and clearing the flag (CL_COPY_UNBINDABLE) in "copy_tree" function in fs/namespace.c. This skips the unbindable mounts to get cloned inside the new namespace. For my use-case this is acceptable.
On Thu, Mar 29, 2018 at 3:50 PM, Ronak Desai <ronak.de...@rockwellcollins.com> wrote: > I came across a problem where if the containers are running then it > affects the unmount process of the system's mount points. I am not > using these mount points as shared mounts with container. > > For example, I am using SD card and NAND as external storage device > and mounting it to a mount point in the ramfs. Then I am launching > containers and then when I try to unmount the NAND partition then my > "unmount" call succeeds but I don't see the UBIFS hooks being called > and because of that my UBI detach process fails. When I stopped the > container then I see that kernel is calling the unmount as I see my > debug prints inside the UBIFS for unmounting that partition. > > If I tried to mount my NAND partition once the container is up and try > to unmount then it does unmount and detach without issue. It seems > like there is an issue with namespace. > > I am using 4.1.8 kernel . I traced the kernel code and I see that > copy_mnt_ns is calling copy_tree and which basically increasing the > active counts of the super block of my host mount points (NAND, SD cards). > I am using container but I do not wish to share any of my host storage > media with > container so in my container configuration I am only mounting the > tmpfs as the rootfs of container is in in tmpfs of host. But, still I > can't umount completely my host storage media if containers are > running. > > I have attached the log of the container start process with debugging > and where you can see it is increasing the super block active counts > for "ubifs". > > -- > Ronak A Desai > Sr. Software Engineer > Airborne Information Solutions / RC Linux Platform Software > MS 131-100, C Ave NE, Cedar Rapids, IA, 52498, USA > > ronak.de...@rockwellcollins.com > > https://www.rockwellcollins.com/ -- Ronak A Desai Sr. Software Engineer Airborne Information Solutions / RC Linux Platform Software MS 131-100, C Ave NE, Cedar Rapids, IA, 52498, USA Phone : 319-263-2667 / VPN : 263-2667 ronak.de...@rockwellcollins.com https://www.rockwellcollins.com/
