Remove zram size limit and disable zswap when using zram

Two fixes that I tested and deployed to build.archlinux.org:

zram-generator: Uncap max size of the zram device

Set "max-zram-size = none" to disable this unwanted limitation which
defaulted to creating zram-based swap with a maximum size of 4096MiB.

Fixes: dc8fa2bdfc86 ("common: Replace deprecated systemd-swap[1] with zram-generator")

zram-generator: use systemd-zram-setup@zram0 handler

Restarting swap.target doesn't apply configuration changes; instead we
can restart systemd-zram-setup@zram0 which seems to do what we wanted.

Bonus commit so that zramctl will display useful statistics:

zram: Disable zswap to prevent conflict with zram
    
When both zswap and zram are active, zswap sits in front of zram and
treats it as a backing store. We just want to use zram and not zswap
disguising itself as such; disable the latter so we can enjoy useful
zramctl statistics.
    
Implemented as tmpfiles.d/zram.conf which disables zswap at runtime.

requested review from @klausenbusk and @jelle

Restarting swap.target doesn't apply configuration changes; instead we can restart systemd-zram-setup@zram0 which seems to do what we wanted.

IIRC restarting swap.target adds the (new) zram devices, but your change is probably what we want.

approved this merge request

added 1 commit

• abb23700 - zram: Disable zswap to prevent conflict with zram

Compare with previous version

Added one more change that disables zswap which was interfering with zram. Deployed it to lists.archlinux.org which complains about swap exhaustion daily, though I don't expect zram to behave much differently than zswap.

changed the description

changed title from Make zram swap great again to Remove max zram size limit and disable zswap when using zram

changed title from Remove max zram size limit and disable zswap when using zram to Remove zram size limit and disable zswap when using zram

approved this merge request

Got rid of all systemd-swap traces that were left on some servers, then deployed the zram config from the MR and verified that each server has 50% of its RAM as zram-based swap.

repro1 has a spacious 447.1G swap partition, so I'll see if we can disable zram on it and rely on zswap instead.

added 6 commits

• abb23700...331314c8 - 3 commits from branch master
• 6fe57bc7 - zram-generator: Uncap max size of the zram device
• 61bdf768 - zram-generator: use systemd-zram-setup@zram0 handler
• bbaa79c6 - zram: Disable zswap to prevent conflict with zram

Compare with previous version

enabled an automatic merge when the pipeline for bbaa79c6 succeeds

mentioned in commit 94334302

merged