6566d1a3 - zram: add dynamic device add/remove functionality

Thu, 25 Jun 2015 22:00:24 +0000

zram: add dynamic device add/remove functionalityWe currently don't support on-demand device creation. The one and onlyway to have N zram devices is to specify num_devices module parameter(default value: 1). IOW if, for some reason, at some point, user wantsto have N + 1 devies he/she must umount all the existing devices, unloadthe module, load the module passing num_devices equals to N + 1. And dothis again, if needed.This patch introduces zram control sysfs class, which has two sysfsattrs:- hot_add -- add a new zram device- hot_remove -- remove a specific (device_id) zram devicehot_add sysfs attr is read-only and has only automatic device idassignment mode (as requested by Minchan Kim). read operation performedon this attr creates a new zram device and returns back its device_id orerror status.Usage example: # add a new specific zram device cat /sys/class/zram-control/hot_add 2 # remove a specific zram device echo 4 > /sys/class/zram-control/hot_removeReturning zram_add() error code back to user (-ENOMEM in this case) cat /sys/class/zram-control/hot_add cat: /sys/class/zram-control/hot_add: Cannot allocate memoryNOTE, there might be users who already depend on the fact that at leastzram0 device gets always created by zram_init(). Preserve this behavior.[minchan@kernel.org: use zram->claim to avoid lockdep splat]Signed-off-by: Sergey Senozhatsky Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-zram

Changes in sysfs-class-zram

6566d1a3 - zram: add dynamic device add/remove functionality