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Bug 1268349 - systemd-readahead touches /.readhead
Summary: systemd-readahead touches /.readhead
Keywords:
Status: CLOSED WONTFIX
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: initscripts
Version: 7.2
Hardware: Unspecified
OS: Unspecified
high
medium
Target Milestone: rc
: ---
Assignee: David Kaspar // Dee'Kej
QA Contact: qe-baseos-daemons
URL:
Whiteboard:
Depends On:
Blocks: 1444018 1465901 1507952 1507957
TreeView+ depends on / blocked
 
Reported: 2015-10-02 15:13 UTC by Fabian Deutsch
Modified: 2018-03-05 14:21 UTC (History)
10 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2018-03-05 14:21:36 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Fabian Deutsch 2015-10-02 15:13:37 UTC 
Description of problem:
It seems that systemd-readahead collect tries to touch/create/write /.readahead.
This leads to an error on systems where / is read-only.

Can't read-ahead touch a different file?

Version-Release number of selected component (if applicable):
RHEL 7

How reproducible:
Always

Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:
Comment 2 Lukáš Nykrýn 2015-10-05 10:33:55 UTC 
Yep we can probably do that. But it is 7.3 material.
Comment 3 Trinh Dao 2017-01-18 21:39:39 UTC 
RH, any update on this bug?
Comment 4 Trinh Dao 2017-01-18 21:42:41 UTC 
HPE bug is 1191750.
Comment 8 Michal Sekletar 2017-04-28 10:13:56 UTC 
I think simple ConditionPathIsReadWrite should do the trick. Hence we would skip collecting read-ahead profile when / is read-only. That would mean users won't get benefits of read-ahead on such systems, but I recon not that many people care for read-ahead these days.

If we use different file then we could run into the same issue.
Comment 10 Michal Sekletar 2017-04-28 14:05:18 UTC 
(In reply to Michal Sekletar from comment #8)
> I think simple ConditionPathIsReadWrite should do the trick. Hence we would
> skip collecting read-ahead profile when / is read-only. That would mean
> users won't get benefits of read-ahead on such systems, but I recon not that
> many people care for read-ahead these days.
> 
> If we use different file then we could run into the same issue.

Lukas pointed out that adding condition doesn't cut it, because we need to check the condition after rootfs was remounted. However we can't simply add After=systemd-remount-fs.service, because that would introduce circular dependency.

We need to figure out something else.
Comment 12 Michal Sekletar 2017-05-04 15:29:31 UTC 
Currently when one enables read-only root via /etc/sysconfig/readonly-root it is still necessary to specify "ro" option for rootfs mount in fstab to actually get read-only filesystem. This is a bug in initscripts. 

Proposed solution is to have generator that parses /etc/sysconfig/readonly-root and changes generated mount unit so that rootfs is actually mounted read-only w/o user intervention in fstab. Same generator could also runtime mask systemd-readahead-collect.service in such case.

Reassigning to initscripts.
Comment 13 Trinh Dao 2017-08-04 20:01:46 UTC 
JoeK, our HPE 1191750 is already closed as won't fix so I am marking HPE verified on this bug.
Comment 16 David Kaspar // Dee'Kej 2017-11-01 09:17:19 UTC 
Hello Joseph,

based on the comment 12 I still don't think this is fixed. If it is really an issue, silently ignoring it might mean than some day in the future it will come back haunting us again (no Halloween reference intended :D).

I'd like to discuss this more with Michal Sekletar when he's back, so I would keep this BZ open for now. :)

 -- Dee'Kej --
Comment 17 David Kaspar // Dee'Kej 2018-03-05 14:21:36 UTC 
After a discussion with Lukas we have decided to close this BZ as WONTFIX. The HPE bug is already closed, and upstream no longer supports (or cares) about readahead, so there's high chance it won't be in next major RHEL releases.
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