From 6566d1a32bf725a4fa9119f16270505451ad01ac Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Thu, 25 Jun 2015 15:00:24 -0700 Subject: 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 Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/ABI/testing/sysfs-class-zram | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-zram (limited to 'Documentation/ABI') diff --git a/Documentation/ABI/testing/sysfs-class-zram b/Documentation/ABI/testing/sysfs-class-zram new file mode 100644 index 000000000000..48ddacbe0e69 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-zram @@ -0,0 +1,24 @@ +What: /sys/class/zram-control/ +Date: August 2015 +KernelVersion: 4.2 +Contact: Sergey Senozhatsky +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 +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), or error code. + +What: /sys/class/zram-control/hot_remove +Date: August 2015 +KernelVersion: 4.2 +Contact: Sergey Senozhatsky +Description: + WO attribute. Remove a specific /dev/zramX device, where X + is a device_id provided by user. -- cgit