On 6/6/24 02:54, Alexander Aring wrote:

Hi,

On Mon, Jun 3, 2024 at 5:56 PM Alexander Aring [off-list ref] wrote:

quoted

Recently the DLM subsystem introduced the flag DLM_LSFL_SOFTIRQ for
dlm_new_lockspace() to signal the capability to handle DLM ast/bast
callbacks in softirq context to avoid an additional context switch due
the DLM callback workqueue.

The md-cluster implementation only does synchronized calls above the
async DLM API. That synchronized API should may be also offered by DLM,
however it is very simple as md-cluster callbacks only does a complete()
call for their wait_for_completion() wait that is occurred after the
async DLM API call. This patch activates the recently introduced
DLM_LSFL_SOFTIRQ flag that allows that the DLM callbacks are executed in
a softirq context that md-cluster can handle. It is reducing a
unnecessary context workqueue switch and should speed up DLM in some
circumstance.

Can somebody with a md-cluster environment test it as well? All I was
doing was (with a working dlm_controld cluster env):

mdadm --create /dev/md0 --bitmap=clustered --metadata=1.2
--raid-devices=2 --level=mirror /dev/sda /dev/sdb

sda and sdb are shared block devices on each node.

Create a /etc/mdadm.conf with the content mostly out of:

mdadm --detail --scan

on each node.

Then call mdadm --assemble on all nodes where not "mdadm --create ..." happened.
I hope that is the right thing to do and I had with "dlm_tool ls" a
UUID as a lockspace name with some md-cluster locks being around.

The above setup method is correct.
SUSE doc [1] provides more details on assembling the clustered array.

[1]: https://documentation.suse.com/fr-fr/sle-ha/15-SP5/html/SLE-HA-all/cha-ha-cluster-md.html#sec-ha-cluster-md-create

To bring this new flag upstream, would it be okay to get this through
dlm-tree? I am requesting here for an "Acked-by" tag from the md
maintainers.

I compiled & tested the dlm-tree [2] with SUSE CI env, and didn't see these
patches introduce new issue.

[2]: https://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm.git/log/?h=next

Thanks,
Heming