Bug 2057238

Summary:	KABI: Padding for block structures
Product:	Red Hat Enterprise Linux 9	Reporter:	Ming Lei <minlei>
Component:	kernel	Assignee:	Ming Lei <minlei>
kernel sub component:	Block Layer	QA Contact:	ChanghuiZhong <czhong>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	unspecified
Priority:	unspecified	CC:	ajb, jmoyer, phil, pvlasin, revers, toracat
Version:	9.0	Keywords:	Triaged
Target Milestone:	rc	Flags:	pm-rhel: mirror+
Target Release:	9.0
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	kernel-5.14.0-70.2.1.el9_0	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-05-17 15:46:28 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:

Description Ming Lei 2022-02-23 03:07:12 UTC

Reserving space for block layer related structures, so that we can maintain kabi
for block drivers.

Comment 3 Jeff Moyer 2022-02-23 14:57:00 UTC

Hi, Ming,

In RHEL 9, we will only preserve kabi for z-stream.  In other words, we will NOT preserve kabi from one minor release to the next.  Do you still want to add padding?

Comment 4 Ming Lei 2022-02-24 00:26:52 UTC

(In reply to Jeff Moyer from comment #3)
> Hi, Ming,
> 
> In RHEL 9, we will only preserve kabi for z-stream.  In other words, we will
> NOT preserve kabi from one minor release to the next.  Do you still want to
> add padding?

Hi Jeff,

Will z-stream require feature backporting? If yes, I think we still need to reserve
padding. Also without padding, sometimes it can be hard to backport some bug fix which
may touch public structures. 

So look we still need to reserve padding?

But now the good thing is that we can adjust padding in minor release.


Thanks,
Ming

Comment 5 Jeff Moyer 2022-02-24 14:43:21 UTC

(In reply to Ming Lei from comment #4)
> (In reply to Jeff Moyer from comment #3)
> > Hi, Ming,
> > 
> > In RHEL 9, we will only preserve kabi for z-stream.  In other words, we will
> > NOT preserve kabi from one minor release to the next.  Do you still want to
> > add padding?
> 
> Hi Jeff,
> 
> Will z-stream require feature backporting? If yes, I think we still need to
> reserve padding.

No.  Z-stream is bugfix only.

> Also without padding, sometimes it can be hard to backport some bug
> fix which may touch public structures. 
> 
> So look we still need to reserve padding?

It certainly doesn't hurt to reserve padding.

> But now the good thing is that we can adjust padding in minor release.

We can, but that will only help future z-streams (not existing, released ones).

I'm okay with adding the padding, I just wanted to make sure you were aware of the new policy, and to see what your thoughts were.

Thanks!
Jeff

Comment 6 Ming Lei 2022-02-25 01:07:50 UTC

(In reply to Jeff Moyer from comment #5)
> (In reply to Ming Lei from comment #4)
> > (In reply to Jeff Moyer from comment #3)
> > > Hi, Ming,
> > > 
> > > In RHEL 9, we will only preserve kabi for z-stream.  In other words, we will
> > > NOT preserve kabi from one minor release to the next.  Do you still want to
> > > add padding?
> > 
> > Hi Jeff,
> > 
> > Will z-stream require feature backporting? If yes, I think we still need to
> > reserve padding.
> 
> No.  Z-stream is bugfix only.
> 
> > Also without padding, sometimes it can be hard to backport some bug
> > fix which may touch public structures. 
> > 
> > So look we still need to reserve padding?
> 
> It certainly doesn't hurt to reserve padding.
> 
> > But now the good thing is that we can adjust padding in minor release.
> 
> We can, but that will only help future z-streams (not existing, released
> ones).
> 
> I'm okay with adding the padding, I just wanted to make sure you were aware
> of the new policy, and to see what your thoughts were.

OK, thanks for sharing the new policy.

Given some subsystems have reserved padding for public structure(schedueler, pci,
scsi, cgroup, ...) already, I'd suggest to do that for block player public
structure too.


Thanks,

Comment 16 errata-xmlrpc 2022-05-17 15:46:28 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (new packages: kernel), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2022:3907