[RFC 3/7] zram: add interface to specify backing device

For writeback feature, user should set up backing device before the zram working. This patch enables the interface via /sys/block/zramX/backing_dev. Currently, it supports block device only but it could be enhanced for file as well. Signed-off-by: Minchan Kim ---

[RFC 3/7] zram: add interface to specify backing device

For writeback feature, user should set up backing device before the zram working. This patch enables the interface via /sys/block/zramX/backing_dev. Currently, it supports block device only but it could be enhanced for file as well. Signed-off-by: Minchan Kim --- drivers/block/zram/zram_drv.c