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Bug 1036450

Summary: after live snapshot, a "snapshot=on" block device becomes read-only
Product: Red Hat Enterprise Linux 6 Reporter: Sibiao Luo <sluo>
Component: qemu-kvmAssignee: Jeff Cody <jcody>
Status: CLOSED WONTFIX QA Contact: Virtualization Bugs <virt-bugs>
Severity: low Docs Contact:
Priority: low    
Version: 6.5CC: bsarathy, chayang, juzhang, mazhang, michen, mkenneth, pbonzini, qzhang, rbalakri, virt-maint, xfu
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: 1036449 Environment:
Last Closed: 2015-01-27 17:49:44 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: 1036449    
Bug Blocks:    

Comment 1 Sibiao Luo 2013-12-02 02:52:21 UTC 
It can be reproduced in rhel6.5 host.
host info:
# uname -r  && rpm -q qemu-kvm-rhev
2.6.32-425.el6.x86_64
qemu-kvm-rhev-0.12.1.2-2.415.el6.x86_64

e.g1:...-drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop,readonly=on,snapshot=on -device scsi-hd,drive=drive-data-disk,bus=scsi0.0,channel=0,scsi-id=0,lun=1,id=data-disk
(qemu) info block
drive-data-disk: removable=0 io-status=ok file=/tmp/vl.7d7Gen backing_file=/home/my-data-disk.qcow2 ro=0 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

e.g2:...-drive file=/home/my-data-disk.qcow2,if=none,id=drive-data-disk,format=qcow2,cache=none,aio=native,werror=stop,rerror=stop,readonly=on -device scsi-hd,drive=drive-data-disk,bus=scsi0.0,channel=0,scsi-id=0,lun=1,id=data-disk
(qemu) info block
drive-data-disk: removable=0 io-status=ok file=/home/my-data-disk.qcow2 ro=1 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0
(qemu) snapshot_blkdev drive-data-disk /home/sanpshot
Formatting '/home/sanpshot', fmt=qcow2 size=5368709120 backing_file='/home/my-data-disk.qcow2' backing_fmt='qcow2' encryption=off cluster_size=65536 
(qemu) info block
drive-data-disk: removable=0 io-status=ok file=/home/sanpshot backing_file=/home/my-data-disk.qcow2 ro=1 drv=qcow2 encrypted=0 bps=0 bps_rd=0 bps_wr=0 iops=0 iops_rd=0 iops_wr=0

Best Regards,
sluo
Comment 3 Jeff Cody 2015-01-27 17:49:44 UTC 
snapshot=on and live snapshots behave different.  Since the readonly=on applies to the drive, a live snapshot should still honor that setting, and not change the disk from read-only to read/write.  Running snapshot=on creates a temporary throw-away snapshot.