1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

OverlayFS File-System Proposed For Linux 3.10 Kernel

Linux Kernel

Published on 13 March 2013 08:32 PM EDT
Written by Michael Larabel in Linux Kernel
7 Comments

The Overlay File-System has been in development for several years and is used by some notable Linux distributions, but has yet to be merged into the mainline Linux kernel after having to be pulled a few times in the past. The new plan is to merge OverlayFS for the Linux 3.10 kernel.

With the patches now up to their sixteenth revision, Miklos Szeredi has called upon Linus Torvalds and Al Viro (the VFS maintainer) to consider pulling OverlayFS for inclusion into the Linux 3.10 release.

Szeredi writes in his latest plea with the Linux kernel developers, "It's included in Ubuntu and openSUSE, used by OpenWrt and various other projects. I regularly get emails asking when it will be included in mainline."

Introducing the new Linux file-system is made-up of thirteen patches and the v16 revision to them can be found on the kernel mailing list.

As far as the Overlay File-System approach to a union file-system, the kernel documentation describes itself:
This document describes a prototype for a new approach to providing overlay-filesystem functionality in Linux (sometimes referred to as union-filesystems). An overlay-filesystem tries to present a filesystem which is the result over overlaying one filesystem on top of the other.

The result will inevitably fail to look exactly like a normal filesystem for various technical reasons. The expectation is that many use cases will be able to ignore these differences.

This approach is 'hybrid' because the objects that appear in the filesystem do not all appear to belong to that filesystem. In many cases an object accessed in the union will be indistinguishable from accessing the corresponding object from the original filesystem. This is most obvious from the 'st_dev' field returned by stat(2).

While directories will report an st_dev from the overlay-filesystem, all non-directory objects will report an st_dev from the lower or upper filesystem that is providing the object. Similarly st_ino will only be unique when combined with st_dev, and both of these can change over the lifetime of a non-directory object. Many applications and tools ignore these values and will not be affected.
Linus Torvalds looks like he may finally pull the file-system for Linux 3.10. He already responded to the thread:
Yes, I think we should just do it. It's in use, it's pretty small, and the other alternatives are worse. Let's just plan on getting this thing done with.

Al, I realize you may not love this, but can you please give this alook? People clearly want to use it. In particular the new interfaces, like the inode ops open function with dentry passed in or whatever? The changes outside of overlayfs looked fine to me.
Al's response at the moment is, "I'll post a review tonight or tomorrow. FWIW, I was not too happy with it the last time I looked, but I'll obviously need to reread the whole thing."

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. Acer B286HK: A 28-inch UHD LED 4K Monitor For As Low As $350
  2. Intel Xeon E5-1680 v3 & E5-2687W v3 Compared To The Core i7 5960X On Linux
  3. Intel 120GB 530 Series SSD Linux Performance
  4. Btrfs/EXT4/XFS/F2FS RAID 0/1/5/6/10 Linux Benchmarks On Four SSDs
Latest Linux Articles
  1. Mesa Git Yields Performance Improvements For Newer AMD GPUs
  2. Apple OS X 10.10 vs. Ubuntu 14.10 Performance
  3. Mesa 10.5-devel Brings Some Intel Haswell HD Graphics Changes Over Mesa 10.3
  4. NVIDIA vs. Nouveau Drivers With Linux 3.18 + Mesa 10.4-devel
Latest Linux News
  1. Jolla Tablet Could Have Upgrades For MicroSDHC, Split Screen, 3.5G
  2. Intel Has Last Round Of DRM Changes For Linux 3.19, Starts Dropping DRI1/UMS
  3. Fedora 21 Release Candidate 1 Awaits Your Testing
  4. GCC 5 Adds Support For ARM's Cortex-A17
  5. KWayland Server Component Coming For KDE Plasma 5.2
  6. NVIDIA Posts Tegra Gallium3D Patch For K1+ Support
  7. Ubuntu 14.10 MacBook Air Tests With Linux 3.18, Mesa 10.5
  8. AMD Richland APU Support Added To Coreboot
  9. 2014 Holiday Shopping Reminder, Happy Thanksgiving
  10. Python 3 Support Added To The GNOME Shell
Latest Forum Discussions
  1. Aliens vs predator for Linux
  2. Updated and Optimized Ubuntu Free Graphics Drivers
  3. Hurrican SDL Port
  4. Roadmap to Catalyst 14.10 ?
  5. how to configure module phoromatic ?
  6. PulseAudio 6.0 Is Coming & Other Linux Audio Plans For The Future
  7. Debian Developer Resigns From The Systemd Maintainership Team
  8. Cant get working Kaveri APU - A10-7850k