lightnvm: pblk: set conservative threshold for user writes
In a worst-case scenario (random writes), OP% of sectors in each line will be invalid, and we will then need to move data out of 100/OP% lines to free a single line. So, to prevent the possibility of running out of lines, temporarily block user writes when there is less than 100/OP% free lines. Also ensure that pblk creation does not produce instances with insufficient over provisioning. Insufficient over-provising is not a problem on real hardware, but often an issue when running QEMU simulations (with few lines). 100 lines is enough to create a sane instance with the standard (11%) over provisioning. Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com> Reviewed-by: Javier González <javier@javigon.com> Signed-off-by: Matias Bjørling <mb@lightnvm.io> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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