Bug 2046431

Summary:	Mounting XFS created by RHEL9 fails in RHEL8 even in read-only mode
Product:	Red Hat Enterprise Linux 8	Reporter:	Filip Pokryvka <fpokryvk>
Component:	kernel	Assignee:	fs-maint
kernel sub component:	XFS	QA Contact:	Zorro Lang <zlang>
Status:	CLOSED NEXTRELEASE	Docs Contact:
Severity:	unspecified
Priority:	unspecified	CC:	esandeen, jke, xzhou
Version:	8.6
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:		Doc Type:	If docs needed, set a value
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Clone Of:		Environment:
Last Closed:	2022-02-25 17:59:31 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 Filip Pokryvka 2022-01-26 16:44:47 UTC

Description of problem:
Mounting XFS partition formatted on RHEL9 fails, it is not even possible mount in read-only mode (regression when comparing RHEL7-RHEL8 case).

Version-Release number of selected component (if applicable):
kernel-4.18.0-357.el8.x86_64

How reproducible:
always

Steps to Reproduce:
1. create XFS partition using RHEL9 (USB flash drive should suffice, I have RHEL9 installed on another partition)
2. boot to RHEL8 (or insert created USB to RHEL8 system)
3. try to mount
4. try to mount read-only

Actual results:
step 3. fails, dmesg:
[   93.310468] XFS (dm-4): Superblock has unknown read-only compatible features (0x8) enabled.
[   93.310476] XFS (dm-4): Attempted to mount read-only compatible filesystem read-write.
[   93.310479] XFS (dm-4): Filesystem can only be safely mounted read only.
[   93.310485] XFS (dm-4): SB validate failed with error -22.

step 4. fails, dmesg:
[  170.593298] XFS (dm-4): Superblock has unknown read-only compatible features (0x8) enabled.
[  170.593306] XFS (dm-4): Superblock has unknown incompatible features (0x8) enabled.
[  170.593309] XFS (dm-4): Filesystem cannot be safely mounted by this kernel.
[  170.593315] XFS (dm-4): SB validate failed with error -22.

Expected results:
at least read-only should be possible, as it is when mounting RHEL8 partition in RHEL7.

Comment 2 Filip Pokryvka 2022-01-27 04:55:14 UTC

Newer kernel mounts RHEL9 partition read-write. Thank you!

Comment 3 Eric Sandeen 2022-02-25 17:59:31 UTC

Yes, RHEL8.6 and newer kernels will have the capability to mount filesystems with these new features. (It's really not a bug for older kernels to be unable to mount newer formats; that is by design.)

So this is either NOTABUG or NEXTRELEASE, I'll close it NEXTRELEASE since this will be resolved in RHEL8.6.