Bug 155427 – kernel dm-multipath: How to handle IO barriers?

Bug 155427 - kernel dm-multipath: How to handle IO barriers?

Summary:	kernel dm-multipath: How to handle IO barriers?

Status:	CLOSED CURRENTRELEASE

Aliases:	None

Product:	Fedora
Classification:	Fedora
Component:	device-mapper-multipath (Show other bugs)
Sub Component:
Version:	rawhide
Hardware:	All Linux

Priority	medium Severity medium
Target Milestone:	---
Target Release:	---
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)
CC List:	7 users (show)

See Also:
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
Add an attachment (proposed patch, testcase, etc.)

Groups: 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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