diff options
author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2015-06-25 15:00:24 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-06-25 17:00:36 -0700 |
commit | 6566d1a32bf725a4fa9119f16270505451ad01ac (patch) | |
tree | c2faa0b705f3da2d0cb10f520127f41df17e7148 /Documentation/blockdev | |
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/blockdev')
-rw-r--r-- | Documentation/blockdev/zram.txt | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 65e94301e57b..c4de576093af 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -99,7 +99,24 @@ size of the disk when not in use so a huge zram is wasteful. mkfs.ext4 /dev/zram1 mount /dev/zram1 /tmp -7) Stats: +7) Add/remove zram devices + +zram provides a control interface, which enables dynamic (on-demand) device +addition and removal. + +In order to add a new /dev/zramX device, perform read operation on hot_add +attribute. This will return either new device's device id (meaning that you +can use /dev/zram<id>) or error code. + +Example: + cat /sys/class/zram-control/hot_add + 1 + +To remove the existing /dev/zramX device (where X is a device id) +execute + echo X > /sys/class/zram-control/hot_remove + +8) Stats: Per-device statistics are exported as various nodes under /sys/block/zram<id>/ A brief description of exported device attritbutes. For more details please @@ -174,11 +191,11 @@ line of text and contains the following stats separated by whitespace: zero_pages num_migrated -8) Deactivate: +9) Deactivate: swapoff /dev/zram0 umount /dev/zram1 -9) Reset: +10) Reset: Write any positive value to 'reset' sysfs node echo 1 > /sys/block/zram0/reset echo 1 > /sys/block/zram1/reset |