Bug 894253

Summary:	Missing error message in bdrv_commit to read-only backing file
Product:	Red Hat Enterprise Linux 7	Reporter:	Sibiao Luo <sluo>
Component:	qemu-kvm	Assignee:	Jeff Cody <jcody>
Status:	CLOSED UPSTREAM	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	7.0	CC:	acathrow, areis, bsarathy, jcody, juzhang, kwolf, michen, mkenneth, qzhang, rhod, sluo, virt-maint, ypu
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	856505	Environment:
Last Closed:	2013-08-27 21:41:06 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:

Comment 1 Sibiao Luo 2013-01-11 08:25:07 UTC

host info:
# uname -r && rpm -q qemu-kvm
3.6.0-0.29.el7.x86_64
qemu-kvm-1.3.0-3.el7.x86_64
guest info
# uname -r
3.6.0-0.29.el7.x86_64

Steps:
1. boot up guest with a readonly=on data image with snapshot=on.
e.g:...-drive file=/home/my-data-disk.qcow2,if=none,format=qcow2,id=drive-virtio0-0-0,media=disk,cache=none,readonly=on,snapshot=on -device virtio-blk-pci,bus=pci.0,addr=0x8,drive=drive-virtio0-0-0,id=virtio0-0-0
2. dd a file in the guest to the data disk.
3. do commit in monitor.
(qemu) info block
drive-system-disk: removable=0 io-status=ok file=/home/RHEL-7-Server-x86_64.qcow2 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
drive-virtio0-0-0: removable=0 io-status=ok file=/tmp/vl.jpdcow backing_file=/home/my-data-disk.qcow2 backing_file_depth=1 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
ide1-cd0: removable=1 locked=0 tray-open=0 io-status=ok [not inserted]
floppy0: removable=1 locked=0 tray-open=0 [not inserted]
sd0: removable=1 locked=0 tray-open=0 [not inserted]
(qemu) ? commit 
commit device|all -- commit changes to the disk images (if -snapshot is used) or backing files
(qemu) commit drive-virtio0-0-0

Expected result:
should fail to commit to a read-only disk with an error message prompts mentioned that backing image is read-only.

Comment 2 Sibiao Luo 2013-01-11 08:32:52 UTC

(In reply to comment #1)
> 
> Expected result:
> should fail to commit to a read-only disk with an error message prompts
> mentioned that backing image is read-only.

check the data disk size and modify time in host, but there is no any changes before and after commit.
- before step 1:
# ls -l /home/my-data-disk.qcow2
-rw-r--r--. 1 root root 8725790720 Jan 10 11:09 /home/my-data-disk.qcow2
- after step 3:
# ls -l /home/my-data-disk.qcow2
-rw-r--r--. 1 root root 8725790720 Jan 10 11:09 /home/my-data-disk.qcow2

Comment 3 Sibiao Luo 2013-01-11 09:51:00 UTC

*** Bug 894251 has been marked as a duplicate of this bug. ***

Comment 4 Sibiao Luo 2013-01-11 09:51:20 UTC

*** Bug 894250 has been marked as a duplicate of this bug. ***

Comment 5 Jeff Cody 2013-01-15 22:32:31 UTC

For completeness, from BZ #856505:

In bdrv_commit(), we are (appropriately) refusing to write to the backing file (in this case, the top-level snapshot, as the active layer is a temp image).  The function bdrv_reopen() returns an error, and bdrv_commit() returns -EACCES.

However, do_commit(), which is the message handler that calls bdrv_commit(), only checks for -EBUSY when it comes to returning an error message.

Comment 6 Jeff Cody 2013-01-18 19:40:03 UTC

Patch submitted upstream:
https://lists.gnu.org/archive/html/qemu-devel/2013-01/msg03456.html