Lines Matching full:is
8 The goal of autofs is to provide on-demand mounting and race free
12 1. There is no need to delay boot until all filesystems that
15 continue freely. This is particularly important for
30 The "autofs" filesystem module is only one part of an autofs system.
38 "autofs" is a Linux kernel module which provides the "autofs"
52 directory should be a mount trap is based on a master map. This master
53 map is consulted by autofs to determine which directories are mount
55 On most systems, the default master map is located at */etc/auto.master*.
58 mount is considered to be *indirect*), then the root directory is
59 always a regular directory, otherwise it is a mount trap when it is
61 *offset* are treated identically so a concise summary is that the root
62 directory is a mount trap only if the filesystem is mounted *direct*
63 and the root is empty.
66 filesystem is mounted *indirect* and they are empty.
69 option and particularly whether it is less than five or not.
70 When *maxproto* is five, no directories further down the
72 the *maxproto* is four (or three), these directories are mount traps
83 A core element of the implementation of autofs is the Mount Traps
91 the inode has S_AUTOMOUNT set, or can be set directly) then it is
94 to be called. The task of this method is to find the filesystem that
95 should be mounted on the directory and to return it. The VFS is
102 everything is ready. It will then return "`NULL`" indicating that the
104 follows down the mount that is already there.
106 This functionality is sufficient for some users of mount traps such
108 reflected on the client. However it is not sufficient for autofs. As
109 mounting onto a directory is considered to be "beyond a `stat`", the
112 that purpose there is another flag.
120 Firstly, before checking to see if any filesystem is mounted on the
124 - A return value of zero indicates that there is nothing special
138 lookup is the automount daemon and that the mount has been
139 requested but has not yet completed. How it determines this is
143 There is a subtlety here. It is possible that a second autofs
152 mount trap, either because it is a symbolic link or because it is
155 - Any other negative value is treated as an error and returned
170 An RCU-walk is a fast and lightweight process for walking down a
171 filename path (i.e. it is like running on tip-toes). RCU-walk cannot
173 to "REF-walk", which is slower but more robust.
177 To determine if a mount-trap is safe for RCU-walk mode it calls
181 spinlocks if at all possible. Its sole purpose is to determine if it
183 reason that it might not be is if an expiry of the mount is
187 VFS that this is a directory that doesn't require d_automount. If
194 -ECHILD if there is any reason to believe it is unsafe to enter the
198 initiated or is being considered, otherwise it returns 0.
206 This is guided by the MNT_SHRINKABLE flag. This only applies to
224 or removal is successful the filesystem will be returned to the state
228 filesystem would, so an attempt to access a recently-removed object is
231 With version 5, this is not safe except for unmounting from top-level
233 processes will see an empty directory as soon as the filesystem is
234 unmounted. So it is generally safest to use the autofs expiry
241 out where it points to. For directories the field is used slightly
242 differently. The field is updated at mount time and during expire
243 checks if it is found to be in use (ie. open file descriptor or
254 The daemon is able to ask autofs if anything is due to be expired,
261 There is an option with indirect mounts to consider each of the leaves
272 mounted, though this check is ignored in some cases. It also checks if
273 the directory or anything below it is in use. For symbolic links,
274 only the `last_used` time is ever considered.
277 is taken.
279 There are two ways to ask autofs to consider expiry. The first is to
284 name normally. As described above, this is unsafe for non-toplevel
296 While the ioctl is blocking, the entry is marked as "expiring" and
307 autofs knows whether a process requesting some operation is the daemon
310 When an autofs filesystem is mounted the pgid of the mounting
311 processes is recorded unless the "pgrp=" option is given, in which
312 case that number is recorded instead. Any request arriving from a
313 process in that process group is considered to come from the daemon.
320 When an autofs filesystem is mounted, the 'write' end of a pipe must
323 For version 5, the format of the message is::
338 And the format of the header is::
345 where the type is one of ::
352 so messages can indicate that a name is missing (something tried to
359 The `wait_queue_token` is a unique number which can identify a
360 particular request to be acknowledged. When a message is sent over
361 the pipe the affected dentry is marked as either "active" or
362 "expiring" and other accesses to it block until the message is
377 to the ioctl command is the "wait_queue_token" number
385 This mode is also entered if a write to the pipe fails.
390 is really a version number for the implementation.
393 long. The value is used to set the timeout for expiry, and
394 the current timeout value is stored back through the pointer.
397 the filesystem could be unmounted. This is only a hint as
401 as described above, this asks if there is
411 is required. This is filled in with the name of something
413 `errno` is set to `EAGAIN`. Even though a `wait_queue_token`
414 is present in the structure, no "wait queue" is established
415 and no acknowledgment is needed.
417 This is similar to
420 The argument is an integer which can contain two different flags.
427 that the daemon has requested this because it is capable of
431 name to expire. This is only safe when *maxproto* is 4.
436 It is not always possible to open the root of an autofs filesystem,
438 is restarted there is no way for it to regain control of existing
440 need there is a "miscellaneous" character device (major 10, minor 235)
446 Each ioctl is passed a pointer to an `autofs_dev_ioctl` structure::
474 filesystem is identified by the `path`. All other commands identify
475 the filesystem by the `ioctlfd` which is a file descriptor open on the
479 the requested version is supported, and report the maximum version
489 on the root of an autofs filesystem. The filesystem is identified
490 by name and device number, which is stored in `openmount.devid`.
496 if the filesystem is in
499 The process group of the calling process is used to identify the
507 Check if path is a
530 happens if a write to the notification pipe fails, or if it is
533 When entering catatonic mode, the pipe is closed and any pending
541 When the filesystem is mounted a _uid_ and _gid_ can be given which
543 filesystem is in catatonic mode, any process with a matching UID can
558 space based on the kernel mount list a no-op mount option ("ignore" is
559 the one use on the most common OSes) is allowed so that autofs file
562 This is intended to be used by user space programs to exclude autofs
568 With bind mounts and name spaces it is possible for an autofs
575 The automount daemon is only able to manage a single mount location for