lightnvm: pblk: check data lines version on recovery
As a preparation for future bumps of data line persistent storage versions, we need to start checking the emeta line version during recovery. Also slit up the current emeta/smeta version into two bytes (major,minor). Recovering lines with the same major number as the current pblk data line version must succeed. This means that any changes in the persistent format must be: (1) Backward compatible: if we switch back to and older kernel, recovery of lines stored with major == current_major and minor > current_minor must succeed. (2) Forward compatible: switching to a newer kernel, recovery of lines stored with major=current_major and minor < minor must handle the data format differences gracefully(i.e. initialize new data structures to default values). If we detect lines that have a different major number than the current we must abort recovery. The user must manually migrate the data in this case. Previously the version stored in the emeta header was copied from smeta, which has version 1, so we need to set the minor version to 1. Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com> Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <mb@lightnvm.io> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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