Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #877
Difficulty: Medium
A real-time operating system (RTOS) is an operating system (OS) intended to serve real-time applications that process data as it comes in, typically without buffer delays.
True or False?
Linux & Unix Commands - Search Man Pages

sb_start_pagefault(9) [centos man page]

SB_START_PAGEFAULT(9)						   The Linux VFS					     SB_START_PAGEFAULT(9)

sb_start_pagefault - get write access to a superblock from a page fault SYNOPSIS
void sb_start_pagefault(struct super_block * sb); ARGUMENTS
sb the super we write to DESCRIPTION
When a process starts handling write page fault, it should embed the operation into sb_start_pagefault - sb_end_pagefault pair to get exclusion against file system freezing. This is needed since the page fault is going to dirty a page. This function increments number of running page faults preventing freezing. If the file system is already frozen, the function waits until the file system is thawed. Since page fault freeze protection behaves as a lock, users have to preserve ordering of freeze protection and other filesystem locks. It is advised to put sb_start_pagefault close to mmap_sem in lock ordering. Page fault HANDLING CODE IMPLIES LOCK DEPENDENCY
mmap_sem -> sb_start_pagefault COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 SB_START_PAGEFAULT(9)

Check Out this Related Man Page

FREEZE_SUPER(9) 						   The Linux VFS						   FREEZE_SUPER(9)

freeze_super - lock the filesystem and force it into a consistent state SYNOPSIS
int freeze_super(struct super_block * sb); ARGUMENTS
sb the super to lock DESCRIPTION
Syncs the super to make sure the filesystem is consistent and calls the fs's freeze_fs. Subsequent calls to this without first thawing the fs will return -EBUSY. During this function, sb->s_writers.frozen goes through these values: SB_UNFROZEN File system is normal, all writes progress as usual. SB_FREEZE_WRITE The file system is in the process of being frozen. New writes should be blocked, though page faults are still allowed. We wait for all writes to complete and then proceed to the next stage. SB_FREEZE_PAGEFAULT Freezing continues. Now also page faults are blocked but internal fs threads can still modify the filesystem (although they should not dirty new pages or inodes), writeback can run etc. After waiting for all running page faults we sync the filesystem which will clean all dirty pages and inodes (no new dirty pages or inodes can be created when sync is running). SB_FREEZE_FS The file system is frozen. Now all internal sources of fs modification are blocked (e.g. XFS preallocation truncation on inode reclaim). This is usually implemented by blocking new transactions for filesystems that have them and need this additional guard. After all internal writers are finished we call ->freeze_fs to finish filesystem freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is mostly auxiliary for filesystems to verify they do not modify frozen fs. sb->s_writers.frozen is protected by sb->s_umount. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 FREEZE_SUPER(9)

15 More Discussions You Might Find Interesting

1. Fedora

Is UNIX an open source OS ?

Hi everyone, I know the following questions are noobish questions but I am asking them because I am confused about the basics of history behind UNIX and LINUX. Ok onto business, my questions are-: Was/Is UNIX ever an open source operating system ? If UNIX was... (21 Replies)
Discussion started by: sreyan32
21 Replies

2. UNIX for Beginners Questions & Answers

Weird 'find' results

Hello and thanks in advance for any help anyone can offer me I'm trying to learn the find command and thought I was understanding it... Apparently I was wrong. I was doing compound searches and I started getting weird results with the -size test. I was trying to do a search on a 1G file owned by... (14 Replies)
Discussion started by: bodisha
14 Replies

3. UNIX for Beginners Questions & Answers

Set hard block limit for user using quota

hi all, i have installed quota on my centos 7 machine and its what im after (setting size limit on users, so they cant fill the hard drive) i want to now make this part of my create user script for my sftp server so i want to do a echo and a read command so i capture the limit they enter... (0 Replies)
Discussion started by: robertkwild
0 Replies

4. UNIX for Beginners Questions & Answers

Best performance UNIX just for HOST Virtualization?

Hi everybody, Which Unix base OS have best performance for HOST virtualization? I tested SmartOS but it needs another OS to connect remotely! Thanks in advance. (11 Replies)
Discussion started by: mbzadegan
11 Replies

5. UNIX for Beginners Questions & Answers

How to increment version inside a file?

Hi All, I need to write a shell script which opens a file and increments the version(text) within the file every time the script runs. For example: $ cat docker_file.yml version: '3.1' services: ui: image: $ So, I would like... (6 Replies)
Discussion started by: akshayupadhayay
6 Replies

6. Programming

DB2 convert digits to binary format

Dear Team We use DB2 v10.5 and using DBArtisan tool Can someone please guide how to convert digits to binary numbers using db2 feature. Ex> for number 9 , binary should be 1001 ( 8+1) Any help appreciated. Thanks (2 Replies)
Discussion started by: Perlbaby
2 Replies

7. UNIX for Advanced & Expert Users

Tar Command

hi folks, how to using tar with exclude directory and compress it using tar.Z i only know how to exclude dir only with this command below: tar -cvf /varios/restore/test.tar -X excludefile.txt /jfma/test1/ how to compress it using 1 command? Thanx Please use CODE tags as... (6 Replies)
Discussion started by: only
6 Replies

8. UNIX for Advanced & Expert Users

CentOS7 restoring file capabilities

Quite an obscure question I think. We have a rebuild process for remote sites that allows us to PXE rebuild a till (actually a PC with a touch screen and various fancy bits) running CentOS. The current CentOS5 tills work just fine with a tar image restore and some personalisation. Sadly,... (4 Replies)
Discussion started by: rbatte1
4 Replies

9. Docker

Docker learning Phase-I

Hello All, I had recently learnt a bit of Docker(which provides containerization process). Here are some of my learning points from it. Let us start first with very basic question: What is Docker: Docker is a platform for sysadmins and developers to DEPLOY, DEVELOP and RUN applications ... (7 Replies)
Discussion started by: RavinderSingh13
7 Replies

10. UNIX for Advanced & Expert Users

Shopt -s histappend

What is the point of this? Whenever I close my shell it appends to the history file without adding this. I have never seen it overwrite my history file. # When the shell exits, append to the history file instead of overwriting it shopt -s histappend (3 Replies)
Discussion started by: cokedude
3 Replies

11. UNIX for Beginners Questions & Answers

Unsure why access time on a directory change isn't changing

Hello... And thanks in advance for any help anyone can offer me I was trying to work out the differences between displaying modify, access, and change times with the 'ls' command. Everything seems in order when I look at files, but the access time on a directory doesn't seem to change when I... (4 Replies)
Discussion started by: bodisha
4 Replies

12. UNIX for Beginners Questions & Answers

CentOS 6 ran out of space, need to reclaim it

Hello everyone, I am having an issue here with CentOS release 6.6 (Final) that shows all of the space used up, but I can't tell where the space went. Seemingly I am using up 100%, according to df -h Filesystem Size Used Avail Use% Mounted on... (27 Replies)
Discussion started by: DannyBoyCentOS
27 Replies

13. Shell Programming and Scripting

Controlling user input

I'm trying to use a bash script for a psych experiment that involves listening to sound files and responding. If I have something like the code below, how can I make sure that a key press is assigned to RESPONSE only after the second echo statement? for i in 1 2 3; do echo "Ready?" sleep 2 ... (10 Replies)
Discussion started by: darwin_886
10 Replies

14. Shell Programming and Scripting

[TIP] Processing YAML files with yq

After the success of the jq - tool for parsing and manipulating JSON-Data someone wrote a tool called yq, which aims to be the same for YAML, what jq is for JSON. Seems to work fine. I'll definitely give it a chance in future. Example YAML-File: --- !ruby/object:Puppet::Node::Facts ... (1 Reply)
Discussion started by: stomp
1 Replies

15. What is on Your Mind?

Please Welcome Dave Munro to the Moderator Team!

Dear All, I am very pleased to announce that Dave Munro (gull04) is joining the Moderation Team, after being a very valuable member of for 15+ years. Dave is an IT Consultant with 30 years of experience this year, has worked in many of the industry vertical market segments and has... (6 Replies)
Discussion started by: Neo
6 Replies

Featured Tech Videos