1 .. SPDX-License-Identifier: GPL-2.0
2
3 ====================================
4 File system Monitoring with fanotify
5 ====================================
6
7 File system Error Reporting
8 ===========================
9
10 Fanotify supports the FAN_FS_ERROR event type
11 reporting. It is meant to be used by file sys
12 daemons, which listen for these events and tak
13 sysadmin, start recovery) when a file system p
14
15 By design, a FAN_FS_ERROR notification exposes
16 for a monitoring tool to know a problem in the
17 It doesn't necessarily provide a user space ap
18 to verify an IO operation was successfully exe
19 scope for this feature. Instead, it is only m
20 early file system problem detection and report
21
22 When a file system operation fails, it is comm
23 errors to cascade after the initial failure, h
24 log, which is usually the most useful debug da
25 problem. For this reason, FAN_FS_ERROR tries
26 error that occurred for a file system since th
27 it simply counts additional errors. This ensu
28 important pieces of information are never lost
29
30 FAN_FS_ERROR requires the fanotify group to be
31 FAN_REPORT_FID flag.
32
33 At the time of this writing, the only file sys
34 notifications is Ext4.
35
36 A FAN_FS_ERROR Notification has the following
37
38 ::
39
40 [ Notification Metadata (Mandatory) ]
41 [ Generic Error Record (Mandatory) ]
42 [ FID record (Mandatory) ]
43
44 The order of records is not guaranteed, and ne
45 in the future. Therefore, applications must n
46 must be prepared to skip over unknown records.
47 ``samples/fanotify/fs-monitor.c`` for an examp
48
49 Generic error record
50 --------------------
51
52 The generic error record provides enough infor
53 agnostic tool to learn about a problem in the
54 providing any additional details about the pro
55 identified by ``struct fanotify_event_info_hea
56 to FAN_EVENT_INFO_TYPE_ERROR.
57
58 ::
59
60 struct fanotify_event_info_error {
61 struct fanotify_event_info_header hd
62 __s32 error;
63 __u32 error_count;
64 };
65
66 The `error` field identifies the type of error
67 `error_count` tracks the number of errors that
68 suppressed to preserve the original error info
69 notification.
70
71 FID record
72 ----------
73
74 The FID record can be used to uniquely identif
75 the error through the combination of fsid and
76 specific application can use that information
77 procedure. Errors that are not related to an
78 empty file handle of type FILEID_INVALID.
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