Bug 155427 - kernel dm-multipath: How to handle IO barriers?
kernel dm-multipath: How to handle IO barriers?
Status: CLOSED CURRENTRELEASE
Product: Fedora
Classification: Fedora
Component: device-mapper-multipath (Show other bugs)
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medium Severity medium
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Assigned To: Alasdair Kergon
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Reported: 2005-04-20 04:52 EDT by Lars Marowsky-Bree
Modified: 2007-11-30 17:11 EST (History)
7 users (show)

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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 10:27:07 EST
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Attachments (Terms of Use)
Make dm-multipath report barriers as "not supported" (1.99 KB, patch)
2005-04-20 08:05 EDT, Lars Marowsky-Bree
no flags Details | Diff

  None (edit)
Description Lars Marowsky-Bree 2005-04-20 04:52:41 EDT
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 08:05:52 EDT
Created attachment 113406 [details]
Make dm-multipath report barriers as "not supported"
Comment 2 Alasdair Kergon 2005-04-21 14:16:54 EDT
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 14:29:43 EDT
Added to 2.6.12-rc2-udm1.

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