Bug 994491 - "lvconvert -r" does not work
"lvconvert -r" does not work
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: lvm2 (Show other bugs)
Unspecified Unspecified
low Severity medium
: rc
: ---
Assigned To: Zdenek Kabelac
: 1006025 (view as bug list)
Depends On:
Blocks: 1006025
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Reported: 2013-08-07 07:40 EDT by Xiaowei Li
Modified: 2016-01-18 13:06 EST (History)
12 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
: 1006025 (view as bug list)
Last Closed: 2016-01-18 13:06:27 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Xiaowei Li 2013-08-07 07:40:57 EDT
Description of problem:
lvconvert does not change the read_ahead to zero after executing "lvconvert --thinpool vg/pool -r none"

"lvchange -r none" works well

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:

[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
  LV   Rahead
  pool     auto 

[root@dhcp12-156 tc]# lvconvert --thinpool vg/pool -r none
  Logical volume "pool_tmeta" created
  Logical volume "lvol0" created
  Converted vg/pool to thin pool.
[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
  LV   Rahead
  pool     auto 

[root@dhcp12-156 tc]# lvchange -r none vg/pool
  Logical volume "pool" changed.

[root@dhcp12-156 tc]# lvs vg -oname,lv_read_ahead
  LV   Rahead
  pool     0 

[root@dhcp12-156 tc]# ls -l /dev/mapper/vg-pool
lrwxrwxrwx. 1 root root 7 Aug  7 07:17 /dev/mapper/vg-pool -> ../dm-5
[root@dhcp12-156 tc]# cat /sys/block/dm-5/queue/read_ahead_kb 

Actual results:

Expected results:

Additional info:
Comment 4 Corey Marthaler 2013-09-09 15:49:52 EDT
Yes, this exists on rhel6.5 as well.
Comment 5 Ludek Smid 2014-06-26 06:47:34 EDT
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.
Comment 6 Ludek Smid 2014-06-26 07:16:11 EDT
The comment above is incorrect. The correct version is bellow.
I'm sorry for any inconvenience.

This request was NOT resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you need
to escalate this bug.
Comment 7 Zdenek Kabelac 2014-11-26 05:02:54 EST
There is currently no meaning behind  read-ahead setting for thin-pool.
So before this BZ is fixed we need to check how to deal with this setting in kernel driver first.
Comment 10 Jonathan Earl Brassow 2015-07-22 09:24:14 EDT
This bug will not be resolved for 7.2.  The read-ahead setting for thin-pools makes no sense really, and this bug may simply be CLOSED NOTABUG.

However, there may be some utility in setting read-ahead for a pool, in that thinLVs might inherit the setting from the pool.  (Although, that is better suited to an LVM config setting probably.)  I'll leave this open for a while for some discussion.
Comment 12 Jonathan Earl Brassow 2016-01-18 13:03:43 EST
*** Bug 1006025 has been marked as a duplicate of this bug. ***
Comment 13 Jonathan Earl Brassow 2016-01-18 13:06:27 EST
There is not determination as to what read-ahead should mean for thin-pools and no discussion to resolve it.  I'm closing this bug WONTFIX.  It can be reopened if it is determined that this is a problem.  (See comment 7 and comment 10 for reference.)

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