mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-27 21:14:44 +08:00
9abeae5d44
Stephen Rothwell reported the following warning was introduced by commit
c0baf9ac0b ("docs: Document the FAN_FS_ERROR event").
Documentation/admin-guide/filesystem-monitoring.rst:60: WARNING:
Definition list ends without a blank line; unexpected unindent.
Link: https://lore.kernel.org/r/87y26camhe.fsf@collabora.com
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>
79 lines
3.0 KiB
ReStructuredText
79 lines
3.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
|
|
====================================
|
|
File system Monitoring with fanotify
|
|
====================================
|
|
|
|
File system Error Reporting
|
|
===========================
|
|
|
|
Fanotify supports the FAN_FS_ERROR event type for file system-wide error
|
|
reporting. It is meant to be used by file system health monitoring
|
|
daemons, which listen for these events and take actions (notify
|
|
sysadmin, start recovery) when a file system problem is detected.
|
|
|
|
By design, a FAN_FS_ERROR notification exposes sufficient information
|
|
for a monitoring tool to know a problem in the file system has happened.
|
|
It doesn't necessarily provide a user space application with semantics
|
|
to verify an IO operation was successfully executed. That is out of
|
|
scope for this feature. Instead, it is only meant as a framework for
|
|
early file system problem detection and reporting recovery tools.
|
|
|
|
When a file system operation fails, it is common for dozens of kernel
|
|
errors to cascade after the initial failure, hiding the original failure
|
|
log, which is usually the most useful debug data to troubleshoot the
|
|
problem. For this reason, FAN_FS_ERROR tries to report only the first
|
|
error that occurred for a file system since the last notification, and
|
|
it simply counts additional errors. This ensures that the most
|
|
important pieces of information are never lost.
|
|
|
|
FAN_FS_ERROR requires the fanotify group to be setup with the
|
|
FAN_REPORT_FID flag.
|
|
|
|
At the time of this writing, the only file system that emits FAN_FS_ERROR
|
|
notifications is Ext4.
|
|
|
|
A FAN_FS_ERROR Notification has the following format::
|
|
|
|
::
|
|
|
|
[ Notification Metadata (Mandatory) ]
|
|
[ Generic Error Record (Mandatory) ]
|
|
[ FID record (Mandatory) ]
|
|
|
|
The order of records is not guaranteed, and new records might be added
|
|
in the future. Therefore, applications must not rely on the order and
|
|
must be prepared to skip over unknown records. Please refer to
|
|
``samples/fanotify/fs-monitor.c`` for an example parser.
|
|
|
|
Generic error record
|
|
--------------------
|
|
|
|
The generic error record provides enough information for a file system
|
|
agnostic tool to learn about a problem in the file system, without
|
|
providing any additional details about the problem. This record is
|
|
identified by ``struct fanotify_event_info_header.info_type`` being set
|
|
to FAN_EVENT_INFO_TYPE_ERROR.
|
|
|
|
::
|
|
|
|
struct fanotify_event_info_error {
|
|
struct fanotify_event_info_header hdr;
|
|
__s32 error;
|
|
__u32 error_count;
|
|
};
|
|
|
|
The `error` field identifies the type of error using errno values.
|
|
`error_count` tracks the number of errors that occurred and were
|
|
suppressed to preserve the original error information, since the last
|
|
notification.
|
|
|
|
FID record
|
|
----------
|
|
|
|
The FID record can be used to uniquely identify the inode that triggered
|
|
the error through the combination of fsid and file handle. A file system
|
|
specific application can use that information to attempt a recovery
|
|
procedure. Errors that are not related to an inode are reported with an
|
|
empty file handle of type FILEID_INVALID.
|