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linux_old1/Documentation/ABI/testing/sysfs-class-zram

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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.