linux-imx

Support is available for filesystems that wish to do automounting

support (such as kAFS which can be found in fs/afs/ and NFS in

fs/nfs/). This facility includes allowing in-kernel mounts to be

performed and mountpoint degradation to be requested. The latter can

also be requested by userspace.

​

​

======================

IN-KERNEL AUTOMOUNTING

======================

​

See section "Mount Traps" of  Documentation/filesystems/autofs.txt

​

Then from userspace, you can just do something like:

​

    [root@andromeda root]# mount -t afs \#root.afs. /afs

    [root@andromeda root]# ls /afs

    asd  cambridge  cambridge.redhat.com  grand.central.org

    [root@andromeda root]# ls /afs/cambridge

    afsdoc

    [root@andromeda root]# ls /afs/cambridge/afsdoc/

    ChangeLog  html  LICENSE  pdf  RELNOTES-1.2.2

​

And then if you look in the mountpoint catalogue, you'll see something like:

​

    [root@andromeda root]# cat /proc/mounts

    ...

    #root.afs. /afs afs rw 0 0

    #root.cell. /afs/cambridge.redhat.com afs rw 0 0

    #afsdoc. /afs/cambridge.redhat.com/afsdoc afs rw 0 0

​

​

===========================

AUTOMATIC MOUNTPOINT EXPIRY

===========================

​

Automatic expiration of mountpoints is easy, provided you've mounted the

mountpoint to be expired in the automounting procedure outlined separately.

​

To do expiration, you need to follow these steps:

​

 (1) Create at least one list off which the vfsmounts to be expired can be

     hung.

​

 (2) When a new mountpoint is created in the ->d_automount method, add

     the mnt to the list using mnt_set_expiry()

             mnt_set_expiry(newmnt, &afs_vfsmounts);

​

 (3) When you want mountpoints to be expired, call mark_mounts_for_expiry()

     with a pointer to this list. This will process the list, marking every

     vfsmount thereon for potential expiry on the next call.

​

     If a vfsmount was already flagged for expiry, and if its usage count is 1

     (it's only referenced by its parent vfsmount), then it will be deleted

     from the namespace and thrown away (effectively unmounted).

​

     It may prove simplest to simply call this at regular intervals, using

     some sort of timed event to drive it.

​

The expiration flag is cleared by calls to mntput. This means that expiration

will only happen on the second expiration request after the last time the

mountpoint was accessed.

​