linux/Documentation/ABI/testing/sysfs-class-zram

What:		/sys/class/zram-control/
Date:		August 2015
KernelVersion:	4.2
Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
		The zram-control/ class sub-directory belongs to zram
		device class

What:		/sys/class/zram-control/hot_add
Date:		August 2015
KernelVersion:	4.2
Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
		RO attribute. Read operation will cause zram to add a new
		device and return its device id back to user (so one can
		use /dev/zram<id>), or error code.

What:		/sys/class/zram-control/hot_remove
Date:		August 2015
KernelVersion:	4.2
Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
		WO attribute. Remove a specific /dev/zramX device, where X
		is a device_id provided by user.
zram: add dynamic device add/remove functionality We currently don't support on-demand device creation. The one and only way to have N zram devices is to specify num_devices module parameter (default value: 1). IOW if, for some reason, at some point, user wants to have N + 1 devies he/she must umount all the existing devices, unload the module, load the module passing num_devices equals to N + 1. And do this again, if needed. This patch introduces zram control sysfs class, which has two sysfs attrs: - hot_add -- add a new zram device - hot_remove -- remove a specific (device_id) zram device hot_add sysfs attr is read-only and has only automatic device id assignment mode (as requested by Minchan Kim). read operation performed on this attr creates a new zram device and returns back its device_id or error 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_remove Returning 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 memory NOTE, there might be users who already depend on the fact that at least zram0 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 <sergey.senozhatsky@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 2015-06-26 06:00:24 +08:00			`What: /sys/class/zram-control/`
			`Date: August 2015`
			`KernelVersion: 4.2`
			`Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>`
			`Description:`
			`The zram-control/ class sub-directory belongs to zram`
			`device class`

			`What: /sys/class/zram-control/hot_add`
			`Date: August 2015`
			`KernelVersion: 4.2`
			`Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>`
			`Description:`
			`RO attribute. Read operation will cause zram to add a new`
			`device and return its device id back to user (so one can`
			`use /dev/zram<id>), or error code.`

			`What: /sys/class/zram-control/hot_remove`
			`Date: August 2015`
			`KernelVersion: 4.2`
			`Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>`
			`Description:`
			`WO attribute. Remove a specific /dev/zramX device, where X`
			`is a device_id provided by user.`