+.. SPDX-License-Identifier: GPL-2.0
+====================================================================
Miscellaneous Device control operations for the autofs kernel module
====================================================================
module source you will see a third type called an offset, which is just
a direct mount in disguise) and indirect.
-Here is a master map with direct and indirect map entries:
+Here is a master map with direct and indirect map entries::
-/- /etc/auto.direct
-/test /etc/auto.indirect
+ /- /etc/auto.direct
+ /test /etc/auto.indirect
-and the corresponding map files:
+and the corresponding map files::
-/etc/auto.direct:
+ /etc/auto.direct:
-/automount/dparse/g6 budgie:/autofs/export1
-/automount/dparse/g1 shark:/autofs/export1
-and so on.
+ /automount/dparse/g6 budgie:/autofs/export1
+ /automount/dparse/g1 shark:/autofs/export1
+ and so on.
-/etc/auto.indirect:
+/etc/auto.indirect::
-g1 shark:/autofs/export1
-g6 budgie:/autofs/export1
-and so on.
+ g1 shark:/autofs/export1
+ g6 budgie:/autofs/export1
+ and so on.
For the above indirect map an autofs file system is mounted on /test and
mounts are triggered for each sub-directory key by the inode lookup
But, each entry in direct and indirect maps can have offsets (making
them multi-mount map entries).
-For example, an indirect mount map entry could also be:
+For example, an indirect mount map entry could also be::
-g1 \
- / shark:/autofs/export5/testing/test \
- /s1 shark:/autofs/export/testing/test/s1 \
- /s2 shark:/autofs/export5/testing/test/s2 \
- /s1/ss1 shark:/autofs/export1 \
- /s2/ss2 shark:/autofs/export2
+ g1 \
+ / shark:/autofs/export5/testing/test \
+ /s1 shark:/autofs/export/testing/test/s1 \
+ /s2 shark:/autofs/export5/testing/test/s2 \
+ /s1/ss1 shark:/autofs/export1 \
+ /s2/ss2 shark:/autofs/export2
-and a similarly a direct mount map entry could also be:
+and a similarly a direct mount map entry could also be::
-/automount/dparse/g1 \
- / shark:/autofs/export5/testing/test \
- /s1 shark:/autofs/export/testing/test/s1 \
- /s2 shark:/autofs/export5/testing/test/s2 \
- /s1/ss1 shark:/autofs/export2 \
- /s2/ss2 shark:/autofs/export2
+ /automount/dparse/g1 \
+ / shark:/autofs/export5/testing/test \
+ /s1 shark:/autofs/export/testing/test/s1 \
+ /s2 shark:/autofs/export5/testing/test/s2 \
+ /s1/ss1 shark:/autofs/export2 \
+ /s2/ss2 shark:/autofs/export2
One of the issues with version 4 of autofs was that, when mounting an
entry with a large number of offsets, possibly with nesting, we needed
The control interface is opening a device node, typically /dev/autofs.
All the ioctls use a common structure to pass the needed parameter
-information and return operation results:
-
-struct autofs_dev_ioctl {
- __u32 ver_major;
- __u32 ver_minor;
- __u32 size; /* total size of data passed in
- * including this struct */
- __s32 ioctlfd; /* automount command fd */
-
- /* Command parameters */
- union {
- struct args_protover protover;
- struct args_protosubver protosubver;
- struct args_openmount openmount;
- struct args_ready ready;
- struct args_fail fail;
- struct args_setpipefd setpipefd;
- struct args_timeout timeout;
- struct args_requester requester;
- struct args_expire expire;
- struct args_askumount askumount;
- struct args_ismountpoint ismountpoint;
- };
-
- char path[0];
-};
+information and return operation results::
+
+ struct autofs_dev_ioctl {
+ __u32 ver_major;
+ __u32 ver_minor;
+ __u32 size; /* total size of data passed in
+ * including this struct */
+ __s32 ioctlfd; /* automount command fd */
+
+ /* Command parameters */
+ union {
+ struct args_protover protover;
+ struct args_protosubver protosubver;
+ struct args_openmount openmount;
+ struct args_ready ready;
+ struct args_fail fail;
+ struct args_setpipefd setpipefd;
+ struct args_timeout timeout;
+ struct args_requester requester;
+ struct args_expire expire;
+ struct args_askumount askumount;
+ struct args_ismountpoint ismountpoint;
+ };
+
+ char path[0];
+ };
The ioctlfd field is a mount point file descriptor of an autofs mount
point. It is returned by the open call and is used by all calls except
structure sent from user space.
This structure can be initialized before setting specific fields by using
-the void function call init_autofs_dev_ioctl(struct autofs_dev_ioctl *).
+the void function call init_autofs_dev_ioctl(``struct autofs_dev_ioctl *``).
All of the ioctls perform a copy of this structure from user space to
kernel space and return -EINVAL if the size parameter is smaller than