Everyone who tries to modify mkfs quickly learns that it is a pile
of spaghetti, the only difference in opinion is whether it is a
steaming, cold or rotten pile. This patchset attempts to untangle
the ball of pasta and turn it into a set of clear, obvious
operations that lead to a filesystem being formatted correctly.
The patch series is really in three parts, splitting the code up
into roughly three modules. The first part introduces a mkfs
parameters structure and factors the on-disk formatting code to use
only information in that structure. The second part introduces a
command line input structure and factors the input parsing to use
it. This requires a bunch of temporary code to keep the rest of
the code working. The third part is factoring the input validation
and geometry calculation code to use the input structure and put
the output into the mkfs parameter structure and to remove all the
temporary support code.
The result is three modules - input parsing, validation+calculations
and formatting - with well defined data flow between them. This also
paves the way to supporting config files to set defaults via a
separate (new) module. The overall data flow now looks like this:
Build defaults --\
---> mkfs_default_params -> CLI -> mkfs_params
config file -----/
It is not worth spending a lot of time reviewing the temporary code
that is added - it gets removed before the end of the series. No
attempt has been made to ensure that mkfs works 100% correctly after
each patch is applied - the only guarantee is that it will build
cleanly. It /should/ work if a bisect lands in the middle of the
series, but trying to exhaustively test each patch is OK would take
more effort than it is worth. As such, testing has only been
performed on the whole series.
The new output from mkfs to indicate where it has sourced the
defaults from causes xfstests to have conniptions. This requires
some updates to the mkfs output filters that are already in place
but it is a fairly trivial update. Test xfs/191 has a couple of new
failures, but that is because the new code now correctly parses
things like agsize so that block and sector size based
specifications work with default mkfs values. This will require test
updates.
Future work will be to split the xfs_mkfs.c file into a file per
module (i.e. seperate files for CLI parsing, mkfs formating,
validation+calculation and, finally, one for config file support),
but otherwise the majority of the factoring work is now complete.
Comments, flames, etc all welcome.
-Dave.
Overall Diffstat:
include/libxfs.h | 2
mkfs/xfs_mkfs.c | 4615 ++++++++++++++++++++++++++++++-------------------------
2 files changed, 2578 insertions(+), 2039 deletions(-)
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