Bug 1081435

Summary:

Add dm-cache module to ramdisk when cached LV is used in the stack

Product:

Red Hat Enterprise Linux 7

Reporter:

Marian Csontos <mcsontos>

Component:

dracut

Assignee:

dracut-maint

Status:

CLOSED CURRENTRELEASE

QA Contact:

Release Test Team <release-test-team-automation>

Severity:

unspecified

Docs Contact:

Priority:

unspecified

Version:

7.0

CC:

dracut-maint-list, harald, jbrassow, ljozsa, mbanas, mcsontos, svenkatr

Target Milestone:

Target Release:

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Hardware:

Unspecified

OS:

Unspecified

Whiteboard:

Fixed In Version:

dracut-033-156.el7

Doc Type:

Bug Fix

Doc Text:

Story Points:

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Clone Of:

Environment:

Last Closed:

2014-06-13 12:36:09 UTC

Type:

Bug

Regression:

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Mount Type:

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Documentation:

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CRM:

Verified Versions:

Category:

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oVirt Team:

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RHEL 7.3 requirements from Atomic Host:

Cloudforms Team:

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Target Upstream Version:

Embargoed:

Attachments:

Description	Flags
Proposed patch	none

Description Marian Csontos 2014-03-27 10:12:01 UTC

Description of problem:

Machine with root on cached LV is not bootable at the moment.

dm-cache kernel module is required in the ramdisk to make root FS using cached LV in the stack bootable.

There are few interesting stacks this allows:

- cached LV (thin-LV, RAID, linear)
- thin-LV on a cached pool (POOL_tdata is cached LV (linear or RAID))

Comment 2 Harald Hoyer 2014-03-27 11:35:35 UTC

Created attachment 879424 [details]
Proposed patch

Comment 3 Marian Csontos 2014-03-27 12:30:35 UTC

Thanks Harald, you beat me posting the patch before I managed to test my changes.
Excuse me, actually it is dm-cache-mq which is required.

I would add dm-cache-cleaner too - if there is a problem during boot it would allow merging data from cache to its origin and dropping cache.
*Jon*, is there something else required I missed?

This change is pretty self-contained. Risk of breaking things is close to 0.

The only thing is relevant modules will be included unconditionally making ramdisk slightly larger, am I correct?

Making proper detection of cache modules required can be postponed till 7.1 as it will be somewhat larger patch.

Comment 5 Harald Hoyer 2014-03-27 15:28:29 UTC

dracut-033-156.el7 added  dm-cache-cleaner and dm-cache-mq

Comment 7 Ladislav Jozsa 2014-04-01 13:45:11 UTC

Verified with dracut-033-156.el7. It is possible to boot with machine having rootfs either on thin-lv or cached lv. The following warnings were issued to the console:

[    0.923782] Buffer I/O error on device dm-4, logical block 167920
[    0.926027] Buffer I/O error on device dm-4, logical block 167920
[    2.068079] Buffer I/O error on device dm-4, logical block 167920
[    2.070444] Buffer I/O error on device dm-4, logical block 167920
[    2.323696] Buffer I/O error on device dm-8, logical block 1008
[    2.325884] Buffer I/O error on device dm-8, logical block 1008

Marian, is it expected?

Comment 8 Marian Csontos 2014-04-01 20:48:57 UTC

It is a "feature" - there is an error dm-mapping in the system for each cache-pool - see dmsetup status. And something is trying to read them IIUC - you will see these e.g. when running `blkid`.

Comment 9 Ludek Smid 2014-06-13 12:36:09 UTC

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.