100 lines
4.0 KiB
ReStructuredText
100 lines
4.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
|
|
=====================================
|
|
OCFS2 file system - online file check
|
|
=====================================
|
|
|
|
This document will describe OCFS2 online file check feature.
|
|
|
|
Introduction
|
|
============
|
|
OCFS2 is often used in high-availability systems. However, OCFS2 usually
|
|
converts the filesystem to read-only when encounters an error. This may not be
|
|
necessary, since turning the filesystem read-only would affect other running
|
|
processes as well, decreasing availability.
|
|
Then, a mount option (errors=continue) is introduced, which would return the
|
|
-EIO errno to the calling process and terminate further processing so that the
|
|
filesystem is not corrupted further. The filesystem is not converted to
|
|
read-only, and the problematic file's inode number is reported in the kernel
|
|
log. The user can try to check/fix this file via online filecheck feature.
|
|
|
|
Scope
|
|
=====
|
|
This effort is to check/fix small issues which may hinder day-to-day operations
|
|
of a cluster filesystem by turning the filesystem read-only. The scope of
|
|
checking/fixing is at the file level, initially for regular files and eventually
|
|
to all files (including system files) of the filesystem.
|
|
|
|
In case of directory to file links is incorrect, the directory inode is
|
|
reported as erroneous.
|
|
|
|
This feature is not suited for extravagant checks which involve dependency of
|
|
other components of the filesystem, such as but not limited to, checking if the
|
|
bits for file blocks in the allocation has been set. In case of such an error,
|
|
the offline fsck should/would be recommended.
|
|
|
|
Finally, such an operation/feature should not be automated lest the filesystem
|
|
may end up with more damage than before the repair attempt. So, this has to
|
|
be performed using user interaction and consent.
|
|
|
|
User interface
|
|
==============
|
|
When there are errors in the OCFS2 filesystem, they are usually accompanied
|
|
by the inode number which caused the error. This inode number would be the
|
|
input to check/fix the file.
|
|
|
|
There is a sysfs directory for each OCFS2 file system mounting::
|
|
|
|
/sys/fs/ocfs2/<devname>/filecheck
|
|
|
|
Here, <devname> indicates the name of OCFS2 volume device which has been already
|
|
mounted. The file above would accept inode numbers. This could be used to
|
|
communicate with kernel space, tell which file(inode number) will be checked or
|
|
fixed. Currently, three operations are supported, which includes checking
|
|
inode, fixing inode and setting the size of result record history.
|
|
|
|
1. If you want to know what error exactly happened to <inode> before fixing, do::
|
|
|
|
# echo "<inode>" > /sys/fs/ocfs2/<devname>/filecheck/check
|
|
# cat /sys/fs/ocfs2/<devname>/filecheck/check
|
|
|
|
The output is like this::
|
|
|
|
INO DONE ERROR
|
|
39502 1 GENERATION
|
|
|
|
<INO> lists the inode numbers.
|
|
<DONE> indicates whether the operation has been finished.
|
|
<ERROR> says what kind of errors was found. For the detailed error numbers,
|
|
please refer to the file linux/fs/ocfs2/filecheck.h.
|
|
|
|
2. If you determine to fix this inode, do::
|
|
|
|
# echo "<inode>" > /sys/fs/ocfs2/<devname>/filecheck/fix
|
|
# cat /sys/fs/ocfs2/<devname>/filecheck/fix
|
|
|
|
The output is like this:::
|
|
|
|
INO DONE ERROR
|
|
39502 1 SUCCESS
|
|
|
|
This time, the <ERROR> column indicates whether this fix is successful or not.
|
|
|
|
3. The record cache is used to store the history of check/fix results. It's
|
|
default size is 10, and can be adjust between the range of 10 ~ 100. You can
|
|
adjust the size like this::
|
|
|
|
# echo "<size>" > /sys/fs/ocfs2/<devname>/filecheck/set
|
|
|
|
Fixing stuff
|
|
============
|
|
On receiving the inode, the filesystem would read the inode and the
|
|
file metadata. In case of errors, the filesystem would fix the errors
|
|
and report the problems it fixed in the kernel log. As a precautionary measure,
|
|
the inode must first be checked for errors before performing a final fix.
|
|
|
|
The inode and the result history will be maintained temporarily in a
|
|
small linked list buffer which would contain the last (N) inodes
|
|
fixed/checked, the detailed errors which were fixed/checked are printed in the
|
|
kernel log.
|