zram: add algo parameter support to zram_recompress()

Recompression iterates through all the registered secondary compression
algorithms in order of their priorities so that we have higher chances of
finding the algorithm that compresses a particular page.  This, however,
may not always be best approach and sometimes we may want to limit
recompression to only one particular algorithm.  For instance, when a
higher priority algorithm uses too much power and device has a relatively
low battery level we may want to limit recompression to use only a lower
priority algorithm, which uses less power.

Introduce algo= parameter support to recompression sysfs knob so that
user-sapce can request recompression with particular algorithm only:

  echo "type=idle algo=zstd" > /sys/block/zramX/recompress

Link: https://lkml.kernel.org/r/20221109115047.2921851-11-senozhatsky@chromium.org


Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>