1 .. SPDX-License-Identifier: GPL-2.0
2
3 =================
4 Automount Support
5 =================
6
7
8 Support is available for filesystems that wish
9 support (such as kAFS which can be found in fs
10 fs/nfs/). This facility includes allowing in-k
11 performed and mountpoint degradation to be req
12 also be requested by userspace.
13
14
15 In-Kernel Automounting
16 ======================
17
18 See section "Mount Traps" of Documentation/fi
19
20 Then from userspace, you can just do something
21
22 [root@andromeda root]# mount -t afs \#
23 [root@andromeda root]# ls /afs
24 asd cambridge cambridge.redhat.com
25 [root@andromeda root]# ls /afs/cambrid
26 afsdoc
27 [root@andromeda root]# ls /afs/cambrid
28 ChangeLog html LICENSE pdf RELNOTE
29
30 And then if you look in the mountpoint catalog
31
32 [root@andromeda root]# cat /proc/mount
33 ...
34 #root.afs. /afs afs rw 0 0
35 #root.cell. /afs/cambridge.redhat.com
36 #afsdoc. /afs/cambridge.redhat.com/afs
37
38
39 Automatic Mountpoint Expiry
40 ===========================
41
42 Automatic expiration of mountpoints is easy, p
43 mountpoint to be expired in the automounting p
44
45 To do expiration, you need to follow these ste
46
47 (1) Create at least one list off which the vf
48 hung.
49
50 (2) When a new mountpoint is created in the -
51 the mnt to the list using mnt_set_expiry(
52
53 mnt_set_expiry(newmnt, &afs_vfsmo
54
55 (3) When you want mountpoints to be expired,
56 with a pointer to this list. This will pr
57 vfsmount thereon for potential expiry on
58
59 If a vfsmount was already flagged for exp
60 (it's only referenced by its parent vfsmo
61 from the namespace and thrown away (effec
62
63 It may prove simplest to simply call this
64 some sort of timed event to drive it.
65
66 The expiration flag is cleared by calls to mnt
67 will only happen on the second expiration requ
68 mountpoint was accessed.
69
70 If a mountpoint is moved, it gets removed from
71 mount is made on an expirable mount, the new v
72 expiration list and will not expire.
73
74 If a namespace is copied, all mountpoints cont
75 and the copies of those that are on an expirat
76 same expiration list.
77
78
79 Userspace Driven Expiry
80 =======================
81
82 As an alternative, it is possible for userspac
83 mountpoint (though some will be rejected - the
84 rootfs for example). It does this by passing t
85 umount(). This flag is considered incompatible
86
87 If the mountpoint in question is in referenced
88 umount() or its parent mountpoint, an EBUSY er
89 mountpoint will not be marked for expiration o
90
91 If the mountpoint was not already marked for e
92 error will be given and it won't be unmounted.
93
94 Otherwise if it was already marked and it wasn
95 take place as usual.
96
97 Again, the expiration flag is cleared every ti
98 looks at a mountpoint.
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