Bug 688147
| Summary: | qcow2: Reads fail with backing file smaller than snapshot | |||
|---|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Kevin Wolf <kwolf> | |
| Component: | qemu-kvm | Assignee: | Kevin Wolf <kwolf> | |
| Status: | CLOSED ERRATA | QA Contact: | Virtualization Bugs <virt-bugs> | |
| Severity: | unspecified | Docs Contact: | ||
| Priority: | unspecified | |||
| Version: | 6.1 | CC: | ehabkost, juzhang, mkenneth, tburke, virt-maint | |
| Target Milestone: | rc | |||
| Target Release: | --- | |||
| Hardware: | Unspecified | |||
| OS: | Unspecified | |||
| Whiteboard: | ||||
| Fixed In Version: | qemu-kvm-0.12.1.2-2.151.el6 | Doc Type: | Bug Fix | |
| Doc Text: |
Cause: For a QCOW2 image that is larger than its base image, when handling a read request straddling over the end of the base image, the QCOW2 driver attempts to read beyond the end of the base image.
Consequence: I/O requests that should have succeeded failed.
Fix: qcow2 code changed to properly handle read base image beyond its size.
Result: when using a QCOW2 image that is larger than its base image, when handling a read request straddling over the end of the base image, I/O will succeed.
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Story Points: | --- | |
| Clone Of: | ||||
| : | 698924 (view as bug list) | Environment: | ||
| Last Closed: | 2011-05-19 11:21:21 UTC | Type: | --- | |
| 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: | ||||
| Bug Blocks: | 698924 | |||
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Description
Kevin Wolf
2011-03-16 13:22:27 UTC
Can reproduce this issue with qemu-kvm-0.12.1.2-2.149.el6.x86_64. step 1. create a base.qcow2 with 64 MB and a sn1.qcow2 with 128 MB and base.qcow2 as its backing file #qemu-img create -f qcow2 base.qcow2 64M #qemu-img create -f qcow2 -b base.qcow2 sn1.qcow2 128M 2.read data in sn1.qcow2 #qemu-io -c 'read -v 63M 2M' sn1.qcow2 Results: Found lots of "0xab instead of 0x00" 040ffe20: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe30: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe40: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe50: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe60: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe70: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe80: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffe90: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffea0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffeb0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffec0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffed0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffee0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040ffef0: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040fff00: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ 040fff10: ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ................ Verified using steps as same as comment2 with qemu-kvm-0.12.1.2-2.153.el6.x86_64 After step2 results: all "0x00" even read big than backing file ....................................... 040fff50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fff60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fff70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fff90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fffa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fffb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fffc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fffd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040fffe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 040ffff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ read 2097152/2097152 bytes at offset 66060288 2 MiB, 1 ops; 0.0000 sec (10.851 GiB/sec and 5555.5556 ops/sec)
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
New Contents:
Cause: For a QCOW2 image that is larger than its base image, when handling a read request straddling over the end of the base image, the QCOW2 driver attempts to read beyond the end of the base image.
Consequence: I/O requests that should have succeeded failed.
Fix: qcow2 code changed to properly handle read base image beyond its size.
Result: when using a QCOW2 image that is larger than its base image, when handling a read request straddling over the end of the base image, I/O will succeed.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0534.html An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0534.html |