Bug 1027600

Summary: [RFE][rmmod] if module is in used, rmmod output the dependences
Product: Red Hat Enterprise Linux 7 Reporter: JianHong Yin <jiyin>
Component: kmodAssignee: Václav Pavlín <vpavlin>
Status: CLOSED CANTFIX QA Contact: Red Hat Kernel QE team <kernel-qe>
Severity: medium Docs Contact:
Priority: unspecified    
Version: 7.0CC: jwboyer
Target Milestone: rcKeywords: FutureFeature
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Enhancement
Doc Text:
Story Points: ---
Clone Of:
: 1027601 (view as bug list) Environment:
Last Closed: 2013-12-16 15:15:40 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:
Bug Depends On:    
Bug Blocks: 1027601    

Description JianHong Yin 2013-11-07 08:09:50 UTC
Description of problem:
When we want rmmod the nfsd, the rmmod just tell me module "is in use".
  But not tell me who use it.
[root@dhcp12-144 ~]# rmmod nfsd
rmmod: ERROR: Module nfsd is in use   <<<--- NOT GOOD
[root@dhcp12-144 ~]# rmmod auth_rpcgss
rmmod: ERROR: Module auth_rpcgss is in use by: nfsd   <<<--- GOOD

And my buddy cost more than half an hours to find why can not rmmod,
  Finally we find it used by /proc/fs/nfsd.
Could rmmod output the dependences, if the dependences is not module name?

Version-Release number of selected component (if applicable):
all version in RHEL{5,6,7}

How reproducible:
100%

Steps to Reproduce:
1. rmmod nfsd
2.
3.

Actual results:
[root@dhcp12-144 ~]# rmmod nfsd
rmmod: ERROR: Module nfsd is in use 

Expected results:
[root@dhcp12-144 ~]# rmmod nfsd
rmmod: ERROR: Module nfsd is in use "by: /proc/fs/nfsd"
OR like follow (if difficult to get):
rmmod: ERROR: Module nfsd is in use "by: nil(maybe used by special filesystem)"

Additional info:

Comment 2 Václav Pavlín 2013-12-12 09:16:05 UTC
I am afraid this is not possible. As rmmod can only get the idea whether the module is used or not from refcnt (/sys/module/nfsd/refcnt), which is set by kernel, I don't see any option how to get the information what is actually using the module.

CC'ing Josh Boyer for his opinion.

Comment 3 Josh Boyer 2013-12-12 14:02:12 UTC
I agree with Václav.  The only things rmmod/modprobe have to look at are the refcnt and the module dependency list (holders).  If a module has its refcnt incremented by something other than another module, there is no simple way for rmmod/modprobe -r to determine that.

Comment 4 Václav Pavlín 2013-12-16 15:15:40 UTC
So closing as CANTFIX.