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author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2015-06-25 15:00:24 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-06-25 17:00:36 -0700 |
commit | 6566d1a32bf725a4fa9119f16270505451ad01ac (patch) | |
tree | c2faa0b705f3da2d0cb10f520127f41df17e7148 /Documentation/ABI | |
parent | f405c445a4866caa43101c231721123805a23bbf (diff) | |
download | linux-stable-6566d1a32bf725a4fa9119f16270505451ad01ac.tar.gz linux-stable-6566d1a32bf725a4fa9119f16270505451ad01ac.tar.bz2 linux-stable-6566d1a32bf725a4fa9119f16270505451ad01ac.zip |
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>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r-- | Documentation/ABI/testing/sysfs-class-zram | 24 |
1 files changed, 24 insertions, 0 deletions
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 <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. |