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Bug 1035001 - VHDX: journal log should not be replayed by default, but rather via qemu-img check -r all
Summary: VHDX: journal log should not be replayed by default, but rather via qemu-img ...
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: qemu-kvm
Version: 7.0
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Jeff Cody
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2013-11-26 20:20 UTC by Jeff Cody
Modified: 2014-06-22 22:46 UTC (History)
6 users (show)

Fixed In Version: qemu-kvm-1.5.3-36.el7
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 1063559 (view as bug list)
Environment:
Last Closed: 2014-06-13 11:56:54 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Jeff Cody 2013-11-26 20:20:21 UTC 
The VHDX r/w driver replays dirty log journals on open, if the image file is opened r/w.  The problem with this approach is two-fold:  1.) If the VHDX image format is in a r/o whitelist, then journal logs can not be replayed, and 2) even when the image file is r/w, we may want to allow the image files to be cleaned up without needing to launch a full guest instance in r/w.


The solution for this is pretty straightforward:

1.) Have qemu-img check (.bdrv_check) for VHDX check the log integrity, and replay the log if '-r all' is passed to qemu-img check.

2.) Do not automatically replay the log on .bdrv_open (vhdx_open), and return error if .bdrv_open is called on a VHDX image file that contains a dirty log (even if opened r/w).

3.) Optionally add in a drive option for VHDX, to provide the option of replaying the log on open if desired, if the image is opened r/w.


These changes should be pretty straightforward, and allow for qemu to support VHDX log files even if VHDX is only in the read-only whitelist.
Comment 2 Jeff Cody 2013-12-17 16:38:39 UTC 
Posted upstream:

http://lists.gnu.org/archive/html/qemu-devel/2013-12/msg03087.html

The agreed above behavior is as follows:

1.) If the image is opened r/o, and has a dirty log, provide a helpful error message instructing the user to run qemu-img check -r all, to replay the image.

2.) If the image is opened r/w, and has a dirty log, replay the log automatically as we currently do.


It should be noted that even without the patch above, running qemu-img check r- all on a VHDX image file will replay the log, even though an error is printed about VHDX not supporting 'check'.  This is because prior to that error, the image file was already opened r/w by qemu-img.

The patch posted upstream provides a .bdrv_check() implementation, and a useful error output.
Comment 4 Miroslav Rezanina 2014-01-14 18:42:57 UTC 
Fix included in qemu-kvm-1.5.3-36.el7
Comment 8 Sibiao Luo 2014-02-11 03:07:30 UTC 
Reproduce and verified this issue with the instruction of comment #2 and comment #7.

######Reproduced:
host info:
# uname -r && rpm -q qemu-kvm
3.10.0-76.el7.x86_64
qemu-kvm-1.5.3-35.el7.x86_64

Steps and Results:
1. If the image is opened r/o.
# qemu-img check -f vhdx tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
qemu-img: Could not open 'tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx': Could not open 'tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx': Permission denied

2. If the image is opened r/w.
# qemu-img check -r all tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
qemu-img: This image format does not support checks
# qemu-img check -f vhdx tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
qemu-img: This image format does not support checks


######Verified:
host info:
# uname -r && rpm -q qemu-kvm
3.10.0-76.el7.x86_64
qemu-kvm-1.5.3-45.el7.x86_64

Steps and Results:
1. If the image is opened r/o, and has a dirty log, provide a helpful error message instructing the user to run qemu-img check -r all, to replay the image.
# qemu-img check -f vhdx tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
qemu-img: Could not open 'tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx': VHDX image file 'tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed.  To replay the log, execute:
 qemu-img check -r all 'tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx': Operation not permitted

2. If the image is opened r/w, and has a dirty log, replay the log automatically as we currently do.
# qemu-img check -r all tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
The following inconsistencies were found and repaired:

    0 leaked clusters
    1 corruptions

Double checking the fixed image now...
No errors were found on the image.
# qemu-img check -f vhdx tests_qemu-iotests_sample_images_iotest-dirtylog-10G-4M.vhdx
No errors were found on the image.

Base on above, this issue has been fixed correctly, move to VERIFIED status, please correct me if any mistake, thanks in advance.

Best Regards,
sluo
Comment 10 Ludek Smid 2014-06-13 11:56:54 UTC 
This request was resolved in Red Hat Enterprise Linux 7.0.

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