Hi Artem,
I wanted to check the 'white-space-fixup' and re-reading your documentation before, so got delayed in replying. + my mail got moderated again by mailman..
From: Artem Bityutskiy [mailto:artem.bityutskiy@linux.intel.com]
[...]
If you are worried about fragmentation, we can discuss this separately. You can find more about UBIFS journal in my very old UBIFS presentation, which explains basic ideas behind the UBIFS wandering journal:
http://www.linux-mtd.infradead.org/doc/ubifs.html#L_documentation
There is also Adrian's white paper with some design description there.
Thanks much for reminding me about this. I had read your slides long back, but never dig deep into Adrian's slides. so, this was still in my 'To Read' list. But really appreciate your work and presentation.
[...]
I do not understand the question. There are no problems in your (b), neither in "*_Case-2_" described.
If you meant "*_Case-1_", then yes, there is a piece of doc:
http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo
Basically, "ubiformat" is the "correct" UBI-aware flasher, while u-boot's "nand write" seems to be a dumb flasher. I guess you have 2 options:
- Teach u-boot's "nand write" to skip empty pages, or may be implement
a separate "clever" flashing command.
Yes, I'll try 'Stefano Babic' suggestion of using u-boot UBI tools.
- Use UBIFS's "space fixup" feature. This will cause UBIFS to fix-up
all empty pages by basically copying all partially-used PEBs to different PEBes with empty pages skipping. This will be done on the first mount, only once, and may cause considerable delays.
See http://www.linux-mtd.infradead.org/faq/ubifs.html#L_free_space_fixup
Though I had read about 'white-space-fixup' feature earlier too, But somewhere in back of my mind, I thought it was only for "free PEBs" (erased-blocks which had corrupted or no volume-header). But after re-reading the FAQ page, I realized that 'white-space-fixup' is done for all pages, whether in 'free-PEB' or 'used-PEB'.
So, This solved my problem.. Thanks much..
P.S. Looking at the MTD web-site now, when I am not doing any UBI/UBIFS/MTD work anymore for few years, I am impressed how much stuff I actually documented there :-)
Absolutely agree. Therefore your file-system is so popular.. Especially the MTD and UBI documentation is not only limited to 'how to use it', Instead I think, it has some advanced details, explanations and reasoning which were quite ahead of its time when it was written.
This is something which you and other MTD/UBI/ & UBIFS Authors and Maintainers should be proud of.
Thanks again ..
with regards, pekon