This is primarily to get better test coverage over devices with very
large erase/prog/read sizes. The unfortunate state of the tests is
that most of them rely on a specific block device size, so that
ENOSPC and ECORRUPT errors occur in specific situations.
This should be improved in the future, but at least for now we can
open up some of the simpler tests to run on these different
configurations.
Also added testing over both 0x00 and 0xff erase values in emubd.
Also added a number of small file tests that expose issues prevalent
on NAND devices.
This implements the second step of full dynamic wear-leveling, block
allocation randomization. This is the key part the uniformly distributes
wear across the filesystem, even through reboots.
The entropy actually comes from the filesystem itself, by xoring
together all of the CRCs in the metadata-pairs on the filesystem. While
this sounds like a ridiculous operation, it's easy to do when we already
scan the metadata-pairs at mount time.
This gives us a random number we can use for block allocation.
Unfortunately it's not a great general purpose random generator as the
output only changes every filesystem write. Fortunately that's exactly
when we need our allocator.
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Additionally, the randomization created a mess for the testing
framework. Fortunately, this method of randomization is deterministic.
A very useful property for reproducing bugs.
Adopted buffer followed by size. The other order was original
chosen due to some other functions with a more complicated
parameter list.
This convention is important, as the bd api is one of the main
apis facing porting efforts.
Before, the lfs had multiple paths to determine config options:
- lfs_config struct passed during initialization
- lfs_bd_info struct passed during block device initialization
- compile time options
This allowed different developers to provide their own needs
to the filesystem, such as the block device capabilities and
the higher level user's own tweaks.
However, this comes with additional complexity and action required
when the configurations are incompatible.
For now, this has been reduced to all information (including block
device function pointers) being passed through the lfs_config struct.
We just defer more complicated handling of configuration options to
the top level user.
This simplifies configuration handling and gives the top level user
the responsibility to handle configuration, which they probably would
have wanted to do anyways.
