[PROPOSAL] Start working on the "unstable bits" issue to make UBIFS more robust

[Wolfram Sang]

Start working on the "unstable bits" issue to make UBIFS more robust

; Summary: Start working on the "unstable bits" issue to make UBIFS more robust

; Proposer: Wolfram Sang

== Description ==

UBIFS on top of UBI is today the defacto standard filesystem for flash-based
storage (NOR, NAND) and is already used in many consumer products. It is stable
and well tested. There is one major known issue, though, called "unstable bits"
(see link in related work), often in accordance with power cuts. The problems
involved are complex and even to start tackling them, a concentrated effort is
needed. In the description of "unstable bits", there is already a roadmap
presented and this proposal suggests to pick up the first task:

--- Quote starts

1) Improve the existing power cut emulation infrastructure in UBIFS and start
emulating unstable bits. Start with emulating only one type of unstable bits,
e.g., type 1.

--- Quote ends

When this is in place, it will enable UBIFS developers (and file system
developers in general) to do power cut simulations much more easily and fix
related bugs or implement proper mechanisms. Automated tests will also benefit
from this work.

Given the importance of flash based storage these days, it seems worthwhile to
get the ball rolling regarding "unstable bits".


== Related work ==

* "unstable bits" description - http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits

== Scope ==

3 weeks should be needed to make the general emulation proper. If all goes well,
maybe more types of power cuts could be implemented in that timeframe.

== Contractor Candidates ==

Artem Bityutskiy (current UBI/UBIFS maintainer) already declined, sadly. But he
will be around for reviews etc. Other recently active contributors to MTD/UBI
could probably be asked.

== Comments ==

[[Category:Project proposals 2012]]

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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