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Re: [lvm-devel] LVM2 ./WHATS_NEW libdm/libdm-deptree.c



Dne 21.6.2010 10:54, prajnoha sourceware org napsal(a):
CVSROOT:	/cvs/lvm2
Module name:	LVM2
Changes by:	prajnoha sourceware org	2010-06-21 08:54:32

Modified files:
	.              : WHATS_NEW
	libdm          : libdm-deptree.c

Log message:
	Use early udev synchronisation and update of dev nodes for clustered mirrors.
	


I'd some discussion with Petr about related problems it looks like we have few things here.

1. I believe that cmirrord should be instructed by mirror kernel driver probably after receiving dm message from our activation code - not just automagicaly directly after resume code - as in this moment nodes are not yet ready in filesystem - and because of this 'race' we need to add this hack flag. However this is most probably 'API' redesign issue...

I think this strategy will be used in replicator - once we will start to used daemons like cmirrord for replicator - but we are not there yet...

2. Petr noticed there is not really well documented 'nowatch' rule inside udev, that probably should allow us to set all 'non-toplevel' created nodes as 'non-watched' nodes - thus avoiding potential problem when we get nodes unexpectedly opened by some 'udev' rules. It should be probably possible to use this flag even in the case we create temporary toplevel devices for 'clearing' _mlog while constructing i.e. mirror devices (or replicator logs) - so we should get 'immune' from 'random' tools opening our rather 'private' temporary device and blocking our deactivation code from work as devices get non-zero open count from some watch rule.

Zdenek


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