zram-init fails if zramctl is available but no zstd support

[sedlund]

Same system as in #14 but now with util-linux installed for zramctl suport.

No log, except on console.

In this case with zramctl installed, it will not create a zram device at all.

zramctl in Alpine 3.9.1:

alpine@ip-172-31-43-27:$ zramctl -V
zramctl from util-linux 2.33
alpine@ip-172-31-43-27:$ zramctl --help

Usage:
 zramctl [options] <device>
 zramctl -r <device> [...]
 zramctl [options] -f | <device> -s <size>

Set up and control zram devices.

Options:
 -a, --algorithm **lzo|lz4|lz4hc|deflate|842**   compression algorithm to use
...

alpine@ip-172-31-43-27:~$ cat /proc/swaps
Filename                                Type            Size    Used    Priority

No zstd support.

Maybe defaulting to zstd in the default /etc/conf.d/zram-init might be a bit premature.

[vaeth]

The algorithms shown on the help page of zramctl are not the algorithms which it understands:
zramctl simply attempts to set the passed algorithm argument.
The error message you see is from the kernel: It seems your kernel does not have support for zstd compiled into the zram module. (Or maybe it exists only as a module and you have to modprobe something before?)

[sedlund]

There is a loaded zstd module for btrfs. The alpine kernel seems not to include support for it with zram though, as evidenced by the output from the other issue I posted.

[sedlund]

Oops did not mean to close!

[vaeth]

IMHO, this is not a bug. It is documented which kernel versions can provide support.

Having zstd support in the kernel is not enough for zram. It must also be supported by the crypto API, that is, you will need CONFIG_CRYPTO_ZSTD.

[sedlund]

Thanks for your help with the other things. I will raise this one in the Alpine bug tracker.

Edit - Alpine bug:
https://bugs.alpinelinux.org/issues/10044

[sedlund]

zram support is now compiled in recent alpine kernels.

https://git.alpinelinux.org/aports/commit/?id=4fcd763003fabfbff087413bd82d767b1862b6f9

thanks.