Bug 1966511

Summary:	Add workaround for qemu reduced maximum disk size
Product:	Red Hat Enterprise Linux 9	Reporter:	xinyli
Component:	nbdkit	Assignee:	Virtualization Maintenance <virt-maint>
Status:	CLOSED NOTABUG	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	9.0	CC:	chhu, eblake, juzhou, mxie, rjones, tyan, tzheng, virt-maint, vwu, xiaodwan, zili
Target Milestone:	beta	Keywords:	Triaged
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:	1913740	Environment:
Last Closed:	2021-06-02 02:33:10 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:	1906049, 1913740
Bug Blocks:

Comment 1 Richard W.M. Jones 2021-06-01 17:09:42 UTC

Hi Xinyu,

As far as I know this bug ought to be fixed by nbdkit 1.25.7 in RHEL 9.
Could you share the results of the test?  What was run and what failed?

Comment 2 xinyli 2021-06-02 02:07:38 UTC

Version-Release number of selected component (if applicable):

nbdkit-1.25.7-1.el9.x86_64
qemu-kvm-6.0.0-2.el9.x86_64

Steps to Reproduce:

# nbdkit memory $(( 2**63 - 512 )) --run 'qemu-img info "$uri"'
qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large

# nbdkit memory $(( 2**63 - 2**30 )) --run 'qemu-img info "$uri"'
image: nbd://localhost:10809
file format: raw
virtual size: 8 EiB (9223372035781033984 bytes)
disk size: unavailable

# nbdkit memory $(( 2**63 - 2**30 + 512 )) --run 'qemu-img info "$uri"'
qemu-img: Could not open 'nbd://localhost:10809': Could not refresh total sector count: File too large

Actual results:
as above description

Comment 3 xinyli 2021-06-02 02:33:10 UTC

Verify the bug with builds:
qemu-kvm-5.2.0-2.scrmod+el8.4.0+9296+87860477.wrb210106.x86_64
nbdkit-1.24.0-1.module+el8.4.0+9341+96cf2672.x86_64

Steps:
1.Use nbdkit memory plugin to create the largest possible RAM disk and use qemu-img to check the disk info:
#nbdkit memory $(( 2**63 - 2**30 )) --run 'qemu-img info "$uri"'
image: nbd://localhost:10809
file format: raw
virtual size: 8 EiB (9223372035781033984 bytes)
disk size: unavailable


2.Combine the nbdkit-streaming-plugin with qemu-img
# mkfifo pipe
# cat pipe > out &
[1] 642654
# qemu-img create -f qcow2 qcow2 1G
Formatting 'qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=1073741824 lazy_refcounts=off refcount_bits=16
# nbdkit memory $(( 2**63 - 2**30 )) --run 'qemu-img info "$uri"'
image: nbd://localhost:10809
file format: raw
virtual size: 8 EiB (9223372035781033984 bytes)
disk size: unavailable