[Proposal] Add checkpointing or logging to UBIFS


Tim Bird <tim.bird@...>
 

; Summary: Add checkpointing or logging to UBIFS

; Proposer: Tim Bird

== Description ==
Currently, the UBI file system takes a long time to be ready for use,
due to a badblock scan that takes place during initialization of UBI
(the UBI attach operation).
The scan takes a time that is linearly proportional to the size of
flash. As flash sizes grow, the delay caused by this scan becomes a
problem.

It would be beneficial to eliminate the scan, or make it more scalable,
using some kind of checkpointing or logging.

== Related work ==
* UBIFS
** http://en.wikipedia.org/wiki/UBIFS
** http://lwn.net/Articles/276025/
* UBI2
** see portions of http://www.mjmwired.net/kernel/Documentation/filesystems/ubifs.txt
* Mount times
** http://osl.sed.hu/wiki/ubifs/index.php/Mount_results
** http://elinux.org/images/f/f8/CELFJamboree30-UBIFS_update.pdf

* This proposal was suggested last year, but the project was not done
** See http://elinux.org/CELF_Project_Proposal/UBIFS_mount_time_speedups

=== UBI logging feature submitted by Samsung ===
A developer with Samsung (in India) proposed UBIL - UBI logging - to solve this problem, in April 2010.
* Initial announcement: http://lists.infradead.org/pipermail/linux-mtd/2010-February/029256.html
** performance improvement: http://git.infradead.org/users/brijesh/ubil_results/blob/da4f975b5a2fc5cb2f9398bcb6b4329ba7e8c770:/nand_mount_time.pdf
** patches in April, 2010: http://lists.infradead.org/pipermail/linux-mtd/2010-April/029573.html

I seem to recall someone at the kernel summit (maybe Thomas) telling me that these patches
improved the speed, but still had scalability proportional to the flash size.

== Scope ==
A rough estimate would be 3 months of development and test work, followed
by some work to mainline the changes upstream.

== Contractor Candidates ==
* Thomas Gleixner
* Artem Bityutskiy
* Free Electrons

== Comments ==

[[Category:Project proposals 2011]]

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Network Entertainment
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