[DRBD-user] why do we need to maintain count "mdev->open_cnt"

Lars Ellenberg lars.ellenberg at linbit.com
Thu Jun 16 15:19:05 CEST 2011

On Thu, Jun 16, 2011 at 04:27:56PM +0530, Usha Saratana wrote:
> Could you please anybody tell me what is use of mdev->open_cnt variable in
> DRBD ?


If you are not able to release everything that uses DRBD,
it won't help to patch DRBD kernel code to be able to
demote/deconfigure/unload DRBD.

Find out who is still using it,
and how to get them to drop their references.

Don't just go randomly patching kernel code.

Sure, there may be some in the kernel code as well, but please just
create a reproducible test case, then tell us, and let people familiar
with the kernel code do the patching, if necessary.

To answer the question in the subject:
because we must refuse to be deconfigured if someone still holds
references to our kernel objects. Otherwise, next time they try to use
them, things go *boom*.

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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