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Bug 1452933

Summary: systemctl incorrectly reports "Error: No space left on device" when restarting a service
Product: Red Hat Enterprise Linux 7 Reporter: James Boyle <unixi>
Component: systemdAssignee: systemd-maint
Status: CLOSED WONTFIX QA Contact: qe-baseos-daemons
Severity: medium Docs Contact:
Priority: unspecified    
Version: 7.3CC: systemd-maint-list
Target Milestone: rcKeywords: Triaged
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2021-01-15 07:36:37 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
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Description Flags
reproducer
none
patch none

Description James Boyle 2017-05-20 16:24:05 UTC 
Description of problem:
systemctl incorrectly reports "Error: No space left on device" when restarting a service.  The issue is related to the kernel setting fs.inotify.max_user_watches

Version-Release number of selected component (if applicable):
# rpm -qa |grep systemd
systemd-219-30.el7_3.8.x86_64

How reproducible:
Always

Steps to Reproduce / Actual Results:
(Have Crashplan backup client installed - or another application using up user_watches)
# sysctl fs.inotify.max_user_watches=8192
fs.inotify.max_user_watches = 8192
# systemctl restart ntpd
Error: No space left on device
# sysctl -w fs.inotify.max_user_watches=131072
fs.inotify.max_user_watches = 131072
# systemctl restart ntpd
#

Expected results:
Error message describing the actual root cause of the error condition: max_user_watches exhausted.  

Additional info:
See also BZ# 1316855 and BZ# 894483
Comment 2 Jan Synacek 2017-05-23 09:53:16 UTC 
Created attachment 1281430 [details]
reproducer

Steps to reproduce:
1) Untar the reproducer.
2) $ sh run.sh
3) Observe.

Note that the reproducer sets max_user_watches to 8192. If, by any chance, step 2 doesn't reproduce the issue, any subsequent "systemctl start test" followed by "systemctl stop test" should do it.

The thing here is that systemd simply translates the errno returned by inotify_add_watch(), which is ENOSPC and then translates it into string, which is "No space left on device", as can be seen in the output of "systemctl status test". I think that, in this particular case, it would be reasonable to add one if (r == -ENOSPC) {...} to create a message fitting for this case instead of a general one.
Comment 3 Jan Synacek 2017-05-24 06:20:33 UTC 
Rescheduling this for RHEL-7.5.

(In reply to Jan Synacek from comment #2)
> I think that, in this particular case, it would be
> reasonable to add one if (r == -ENOSPC) {...} to create a message fitting
> for this case instead of a general one.

Unfortunately, after some debugging I found out that it's actually not so trivial to fix this bug.
Comment 4 Jan Synacek 2017-05-25 09:23:24 UTC 
(In reply to Jan Synacek from comment #3)
> Unfortunately, after some debugging I found out that it's actually not so
> trivial to fix this bug.

Scratch that, it is easy to fix, it just wasn't obvious at first sight...

https://github.com/systemd/systemd/issues/6030
Comment 5 Jan Synacek 2017-05-25 09:29:09 UTC 
Created attachment 1282191 [details]
patch

This patch fixes this particular problem, which will probably be enough. I figure that a correct upstream patch would be more general, though.
Comment 8 RHEL Program Management 2021-01-15 07:36:37 UTC 
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.