Bug 2226900

Summary:	mkfs.xfs(8): Update section on dax+reflink compatibility
Product:	Red Hat Enterprise Linux 9	Reporter:	Eric Sandeen <esandeen>
Component:	xfsprogs	Assignee:	Pavel Reichl <preichl>
Status:	VERIFIED ---	QA Contact:	xiaoli feng <xifeng>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	9.3	CC:	billodo, cmaiolin, preichl, xzhou, zlang
Target Milestone:	rc	Keywords:	Triaged
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	xfsprogs-5.19.0-4.el9	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:		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 Eric Sandeen 2023-07-26 21:46:38 UTC

The current version of the mkfs.xfs man page in RHEL9 (and upstream) contains this caveat:

> Note: the filesystem DAX mount option ( -o dax ) is incompatible with reflink-enabled XFS filesystems.  To use  filesystem DAX with XFS, specify the -m reflink=0 option to mkfs.xfs to disable the reflink feature.

This is no longer the case upstream, and with the updates in kernel bug #2192730 it is no longer the case for RHEL9.

We need to send a patch upstream to address this, probably mentioning the kernel version which added dax+reflink support, and add a similar patch to RHEL9.

Thanks,
-Eric

Comment 1 Eric Sandeen 2023-08-01 01:01:42 UTC

The patch to fix this upstream has been sent to the xfs mailing list, and was reviewed by Darrick.

Carlos, if you approve of the change as well, getting it to for-next would be a good next step so that we can backport it to RHEL9.3 fairly soon.

Thanks,
-Eric

Comment 5 Bill O'Donnell 2023-08-02 13:33:09 UTC

Yes, please!

Comment 6 Pavel Reichl 2023-08-02 14:09:20 UTC

Back porting: 780e93c5 mkfs.xfs.8: correction on mkfs.xfs manpage since reflink and dax are compatible

Comment 9 xiaoli feng 2023-08-04 04:59:19 UTC

Find this info in mkfs.xfs of xfsprogs-5.19.0-3.el9.x86_64.
[root@dell-per750-43 xfstests-dev]# rpm -qa xfsprogs
xfsprogs-5.19.0-3.el9.x86_64
[root@dell-per750-43 ~]# man mkfs.xfs |grep -A 2 -i dax
Note: the filesystem DAX mount option ( -o dax ) is incompatible with reflink-enabled XFS filesystems. To use filesystem DAX
with XFS, specify the -m reflink=0 option to mkfs.xfs to disable the reflink feature.

--
daxinherit=value
If value is set to 1, all inodes created by mkfs.xfs will be created with the DAX flag set. The default is 0. Directories will
pass on this flag to newly created regular files and directories. By default, mkfs.xfs will not enable DAX mode.

-f Force overwrite when an existing filesystem is detected on the device. By default, mkfs.xfs will not write to the device if it suspects

Verify on xfsprogs-5.19.0-4.el9
[root@dell-per750-43 ~]# man mkfs.xfs |grep -A 2 -i dax
daxinherit=value
If value is set to 1, all inodes created by mkfs.xfs will be created with the DAX flag set. The default is 0. Directories will
pass on this flag to newly created regular files and directories. By default, mkfs.xfs will not enable DAX mode.

-f Force overwrite when an existing filesystem is detected on the device. By default, mkfs.xfs will not write to the device if it suspects
[root@dell-per750-43 ~]# rpm -qa xfsprogs
xfsprogs-5.19.0-4.el9.x86_64