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From: Cesare Leonardi <celeonar@gmail.com>
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Date: Sun, 25 Nov 2018 00:30:05 +0100
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Subject: [linux-lvm] LVM RAID: task mdX_raid1:221 blocked for more than 120
	seconds
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To: linux-lvm@redhat.com

Since my message did not reach the list, I'm resending, but first I've 
subscribed myself.

------------------
Hello, I'm writing here to have your opinion and possibly some advice 
about some Debian bugs related to LVM RAID that are still unresolved:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=913119
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=913138
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904822

Bug #913119 was filed by me, so I can personally provide some more 
information and do tests.

Premises related di Debian unstable:
* Debian's kernel is currently 4.18.20.
* From kernel 4.17~rc7 Debian enabled SCSI_MQ_DEFAULT and DM_MQ_DEFAULT.
* Debian's LVM userland is 2.02.176

The above reports shows blocked I/O with different type of LVM RAID and 
with #913119 I've succesfully workarounded passing the following kernel 
parameters:
scsi_mod.use_blk_mq=0 dm_mod.use_blk_mq=0

I've read that RHEL will default to enabling SCSI_MQ_DEFAULT and 
DM_MQ_DEFAULT and will use kernel 4.18. Maybe you have already 
encountered this bug and it's already resolved. Or there are patches 
pending.

What do you think? Should I file a bug in Red Hat bug tracker?

Cesare.