1 .. SPDX-License-Identifier: GPL-2.0
2
3 ============================
4 Linux Directory Notification
5 ============================
6
7 Stephen Rothwell <sfr@canb.auug.org.
8
9 The intention of directory notification is to
10 to be notified when a directory, or any of the
11 The basic mechanism involves the application r
12 on a directory using a fcntl(2) call and the n
13 being delivered using signals.
14
15 The application decides which "events" it want
16 The currently defined events are:
17
18 ========= ======================
19 DN_ACCESS A file in the director
20 DN_MODIFY A file in the director
21 DN_CREATE A file was created in
22 DN_DELETE A file was unlinked fr
23 DN_RENAME A file in the director
24 DN_ATTRIB A file in the director
25 changed (chmod,chown)
26 ========= ======================
27
28 Usually, the application must reregister after
29 if DN_MULTISHOT is or'ed with the event mask,
30 remain until explicitly removed (by registerin
31
32 By default, SIGIO will be delivered to the pro
33 information. However, if the F_SETSIG fcntl(2
34 kernel know which signal to deliver, a siginfo
35 the signal handler and the si_fd member of tha
36 file descriptor associated with the directory
37
38 Preferably the application will choose one of
39 (SIGRTMIN + <n>) so that the notifications may
40 especially important if DN_MULTISHOT is specif
41 is often blocked, so it is better to use (at l
42
43 Implementation expectations (features and bugs
44 ----------------------------------------------
45
46 The notification should work for any local acc
47 actual file system is on a remote server. Thi
48 access to files served by local user mode serv
49 Also, remote accesses to files served by a loc
50 be notified.
51
52 In order to make the impact on the file system
53 the problem of hard links to files has been ig
54 exists in two directories (a and b) then a cha
55 name "a/x" should be notified to a program exp
56 directory "a", but will not be notified to one
57 directory "b".
58
59 Also, files that are unlinked, will still caus
60 last directory that they were linked to.
61
62 Configuration
63 -------------
64
65 Dnotify is controlled via the CONFIG_DNOTIFY c
66 disabled, fcntl(fd, F_NOTIFY, ...) will return
67
68 Example
69 -------
70 See tools/testing/selftests/filesystems/dnotif
71
72 NOTE
73 ----
74 Beginning with Linux 2.6.13, dnotify has been
75 See Documentation/filesystems/inotify.rst for
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