1 .. SPDX-License-Identifier: GPL-2.0
2
3 ===============
4 Quota subsystem
5 ===============
6
7 Quota subsystem allows system administrator to
8 number of used inodes (inode is a filesystem s
9 each file or directory) for users and/or group
10 of used inodes there are actually two limits.
11 and the second one hardlimit. A user can neve
12 resource (unless he has CAP_SYS_RESOURCE capab
13 softlimit but only for limited period of time.
14 period" or "grace time". When grace time is ov
15 more space/inodes until he frees enough of the
16
17 Quota limits (and amount of grace time) are se
18 filesystem.
19
20 For more details about quota design, see the d
21 (https://sourceforge.net/projects/linuxquota).
22
23 Quota netlink interface
24 =======================
25 When user exceeds a softlimit, runs out of gra
26 quota subsystem traditionally printed a messag
27 the process which caused the excess. This meth
28 when user is using a graphical desktop he usua
29 Thus quota netlink interface has been designed
30 the above events to userspace. There they can
31 and processed accordingly.
32
33 The interface uses generic netlink framework (
34 https://lwn.net/Articles/208755/ and http://ww
35 more details about this layer). The name of th
36 is "VFS_DQUOT". Definitions of constants below
37 the quota netlink protocol is not namespace aw
38 sent only in initial network namespace.
39
40 Currently, the interface supports only one mes
41 This command is used to send a notification ab
42 events. Each message has six attributes. These
43 in parentheses):
44
45 QUOTA_NL_A_QTYPE (u32)
46 - type of quota being exceeded (one
47 QUOTA_NL_A_EXCESS_ID (u64)
48 - UID/GID (depends on quota type) of
49 is being exceeded.
50 QUOTA_NL_A_CAUSED_ID (u64)
51 - UID of a user who caused the event
52 QUOTA_NL_A_WARNING (u32)
53 - what kind of limit is exceeded:
54
55 QUOTA_NL_IHARDWARN
56 inode hardlimit
57 QUOTA_NL_ISOFTLONGWARN
58 inode softlimit is exceede
59 than given grace period
60 QUOTA_NL_ISOFTWARN
61 inode softlimit
62 QUOTA_NL_BHARDWARN
63 space (block) hardlimit
64 QUOTA_NL_BSOFTLONGWARN
65 space (block) softlimit is
66 longer than given grace pe
67 QUOTA_NL_BSOFTWARN
68 space (block) softlimit
69
70 - four warnings are also defined for
71 exceeding some limit:
72
73 QUOTA_NL_IHARDBELOW
74 inode hardlimit
75 QUOTA_NL_ISOFTBELOW
76 inode softlimit
77 QUOTA_NL_BHARDBELOW
78 space (block) hardlimit
79 QUOTA_NL_BSOFTBELOW
80 space (block) softlimit
81
82 QUOTA_NL_A_DEV_MAJOR (u32)
83 - major number of a device with the
84 QUOTA_NL_A_DEV_MINOR (u32)
85 - minor number of a device with the
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