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SubjectRe: partially encrypted filesystem
Hi!

> > Of course, all this is at the logical file level, and ignores the
> > physical blocks on disk. All filesystems assume physical data blocks
> > can be updated in place. With compression it is possible a new physical
> > block has to be found, especially if blocks are highly packed and not
> > aligned to block boundaries. I expect this is at least partially why
> > JFFS2 is a log structured filesystem.
>
> Not really. JFFS2 is a log structured file system because it's designed
> to work on _flash_, not on block devices. You have an eraseblock size of
> typically 64KiB, you can clear bits in that 'block' all you like till
> they're all gone or you're bored, then you have to erase it back to all
> 0xFF again and start over.
>
> Even if you were going to admit to having a block size of 64KiB to the
> layers above you, you just can't _do_ atomic replacement of blocks,
> which is required for normal file systems to operate correctly.

Are those assumptions needed for something else than recovery after
crash/powerdown? [i.e., afaics 64K ext2 should work on flash, but fsck
might have some troubles...]

Pavel
--
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]
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