1.. SPDX-License-Identifier: GPL-2.0 2 3===================================== 4OCFS2 file system - online file check 5===================================== 6 7This document will describe OCFS2 online file check feature. 8 9Introduction 10============ 11OCFS2 is often used in high-availability systems. However, OCFS2 usually 12converts the filesystem to read-only when encounters an error. This may not be 13necessary, since turning the filesystem read-only would affect other running 14processes as well, decreasing availability. 15Then, a mount option (errors=continue) is introduced, which would return the 16-EIO errno to the calling process and terminate further processing so that the 17filesystem is not corrupted further. The filesystem is not converted to 18read-only, and the problematic file's inode number is reported in the kernel 19log. The user can try to check/fix this file via online filecheck feature. 20 21Scope 22===== 23This effort is to check/fix small issues which may hinder day-to-day operations 24of a cluster filesystem by turning the filesystem read-only. The scope of 25checking/fixing is at the file level, initially for regular files and eventually 26to all files (including system files) of the filesystem. 27 28In case of directory to file links is incorrect, the directory inode is 29reported as erroneous. 30 31This feature is not suited for extravagant checks which involve dependency of 32other components of the filesystem, such as but not limited to, checking if the 33bits for file blocks in the allocation has been set. In case of such an error, 34the offline fsck should/would be recommended. 35 36Finally, such an operation/feature should not be automated lest the filesystem 37may end up with more damage than before the repair attempt. So, this has to 38be performed using user interaction and consent. 39 40User interface 41============== 42When there are errors in the OCFS2 filesystem, they are usually accompanied 43by the inode number which caused the error. This inode number would be the 44input to check/fix the file. 45 46There is a sysfs directory for each OCFS2 file system mounting:: 47 48 /sys/fs/ocfs2/<devname>/filecheck 49 50Here, <devname> indicates the name of OCFS2 volume device which has been already 51mounted. The file above would accept inode numbers. This could be used to 52communicate with kernel space, tell which file(inode number) will be checked or 53fixed. Currently, three operations are supported, which includes checking 54inode, fixing inode and setting the size of result record history. 55 561. If you want to know what error exactly happened to <inode> before fixing, do:: 57 58 # echo "<inode>" > /sys/fs/ocfs2/<devname>/filecheck/check 59 # cat /sys/fs/ocfs2/<devname>/filecheck/check 60 61The output is like this:: 62 63 INO DONE ERROR 64 39502 1 GENERATION 65 66 <INO> lists the inode numbers. 67 <DONE> indicates whether the operation has been finished. 68 <ERROR> says what kind of errors was found. For the detailed error numbers, 69 please refer to the file linux/fs/ocfs2/filecheck.h. 70 712. If you determine to fix this inode, do:: 72 73 # echo "<inode>" > /sys/fs/ocfs2/<devname>/filecheck/fix 74 # cat /sys/fs/ocfs2/<devname>/filecheck/fix 75 76The output is like this::: 77 78 INO DONE ERROR 79 39502 1 SUCCESS 80 81This time, the <ERROR> column indicates whether this fix is successful or not. 82 833. The record cache is used to store the history of check/fix results. It's 84default size is 10, and can be adjust between the range of 10 ~ 100. You can 85adjust the size like this:: 86 87 # echo "<size>" > /sys/fs/ocfs2/<devname>/filecheck/set 88 89Fixing stuff 90============ 91On receiving the inode, the filesystem would read the inode and the 92file metadata. In case of errors, the filesystem would fix the errors 93and report the problems it fixed in the kernel log. As a precautionary measure, 94the inode must first be checked for errors before performing a final fix. 95 96The inode and the result history will be maintained temporarily in a 97small linked list buffer which would contain the last (N) inodes 98fixed/checked, the detailed errors which were fixed/checked are printed in the 99kernel log. 100