On Fri, Oct 23, 2015 at 10:24:05AM +0200, Josef Reidinger wrote: > On Thu, 22 Oct 2015 17:04:35 +0200 > Arvin Schnell <[email protected]> wrote: > > > On Thu, Oct 22, 2015 at 08:59:52AM +0200, Josef Reidinger wrote: > > > > > > You can mount a device at several mount-points. With btrfs this > > > > is even standard, see > > > > https://github.com/openSUSE/libstorage/blob/master/doc/status-current-code.md. > > > > > > Yes, I know that device can have multiple mountpoints, but here is > > > logic reverse. It said that one mount point can have multiple > > > devices ( or filesystem like used here ) which is at least for > > > common usage without overlapper layered mount points not possible. > > > > It is possible, although likely stupid: > > > > cat /proc/mounts > > [...] > > /dev/mapper/system-abuild /mnt ext4 rw,relatime,commit=600 0 0 > > /dev/mapper/system-giant--xfs /mnt xfs > > rw,relatime,attr2,inode64,noquota 0 0 > > > > So the API must be able to handle the situation. Or do you prefer > > an exception during probing? > > I think it is two different things. > > 1) probing should handle such situation > > 2) common query should return only later as first one is overlaped, of > course there can be specialized call to manipulate mount points knowing > also about overlap or knowing that removing first mount point return to > game previous one
Currently the ordering does not define that information. I had a different use-case in mind: If you want to delete /dev/mapper/system-abuild you first have to unmount it. Since umount(2) only supports unmounting the topmost filesystem you also have to unmount /dev/mapper/system-giant--xfs. You have to present that to the user. So you need all filesystems mounted at that place. > I do not look at API from probe POV, but from library user POV, so I > query what device content is visible under /mnt, which answer is only > second one. In general you have to look at the API from both sides. After all the API has to represent the system and not some theoretic concept. Regards, Arvin -- Arvin Schnell, <[email protected]> Senior Software Engineer, Research & Development SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) Maxfeldstraße 5 90409 Nürnberg Germany -- To unsubscribe, e-mail: [email protected] To contact the owner, e-mail: [email protected]
