Bug 155427

Summary: kernel dm-multipath: How to handle IO barriers?
Product: [Fedora] Fedora Reporter: Lars Marowsky-Bree <lmb>
Component: device-mapper-multipathAssignee: Alasdair Kergon <agk>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: agk, bmarzins, christophe.varoqui, dmo, junichi.nomura, kueda, tranlan
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Hardware: All   
OS: Linux   
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Fixed In Version: 2.6.12-rc2-udm1 Doc Type: Bug Fix
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Last Closed: 2006-03-08 15:27:07 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Flags
Make dm-multipath report barriers as "not supported" none

Description Lars Marowsky-Bree 2005-04-20 08:52:41 UTC 
How should IO barriers be handled - should they be short-circuited and disabled
in the mapping function directly, do we want to support them - which would
probably involve sending them down all paths -, or is there another option...?

I'm tending towards short circuiting them.
Comment 1 Lars Marowsky-Bree 2005-04-20 12:05:52 UTC 
Created attachment 113406 [details]
Make dm-multipath report barriers as "not supported"
Comment 2 Alasdair Kergon 2005-04-21 18:16:54 UTC 
We need IO barriers which don't carry any data; then we have to send them down
all the paths that might have unsynced IO on them, leading to fun interactions
with priority groups, switch_pg when paths haven't failed etc.

Until then they don't work so not supported.
Comment 3 Alasdair Kergon 2005-04-21 18:29:43 UTC 
Added to 2.6.12-rc2-udm1.