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[Qemu-block] [PATCH 0/2] qemu-img: Resolve relative backing paths in reb
From: |
Max Reitz |
Subject: |
[Qemu-block] [PATCH 0/2] qemu-img: Resolve relative backing paths in rebase |
Date: |
Wed, 9 May 2018 17:49:47 +0200 |
The issue addressed in this series affects relative backing paths given
to qemu-img rebase. For the rebasing operation itself, qemu-img uses
the target backing path as-is, that is, relative to its working
directory. But after rebasing, the path is again written as-is into the
overlay, so it is now relative to the overlay.
Simple test case:
$ mkdir /tmp/foo && cd /tmp
$ qemu-img create -f qcow2 foo/base-old.qcow2 64M
Formatting 'foo/base-old.qcow2', fmt=qcow2 size=67108864 cluster_size=65536
lazy_refcounts=off refcount_bits=16
$ qemu-img create -f qcow2 foo/base-new.qcow2 64M
Formatting 'foo/base-new.qcow2', fmt=qcow2 size=67108864 cluster_size=65536
lazy_refcounts=off refcount_bits=16
$ qemu-img create -f qcow2 -b base-old.qcow2 foo/overlay.qcow2 64M
Formatting 'foo/overlay.qcow2', fmt=qcow2 size=67108864
backing_file=base-old.qcow2 cluster_size=65536 lazy_refcounts=off
refcount_bits=16
$ qemu-img rebase -b base-new.qcow2 foo/overlay.qcow2
qemu-img: Could not open new backing file 'base-new.qcow2': Could not open
'base-new.qcow2': No such file or directory
Oops. Now one may be tempted to try:
$ qemu-img rebase -b foo/base-new.qcow2 foo/overlay.qcow2
$ echo $?
0
However:
$ qemu-img info foo/overlay.qcow2
[...]
backing file: foo/base-new.qcow2 (actual path: foo/foo/base-new.qcow2)
[...]
$ qemu-io -c close foo/overlay.qcow2
can't open device foo/overlay.qcow2: Could not open backing file: Could not
open 'foo/foo/base-new.qcow2': No such file or directory
Oops.
So the only way to do it before this series is:
$ qemu-img rebase -b foo/base-new.qcow2 foo/overlay.qcow2
$ qemu-img rebase -u -b base-new.qcow2 foo/overlay.qcow2
That does not seem right to me.
So this series makes qemu-img rebase always interpret the target backing
path relatively to the overlay image, because that is how we always
interpret relative backing paths.
Max Reitz (2):
qemu-img: Resolve relative backing paths in rebase
iotests: Add test for rebasing with relative paths
qemu-img.c | 22 ++++++++++++-
tests/qemu-iotests/024 | 82 ++++++++++++++++++++++++++++++++++++++++++++--
tests/qemu-iotests/024.out | 30 +++++++++++++++++
3 files changed, 130 insertions(+), 4 deletions(-)
--
2.14.3
- [Qemu-block] [PATCH 0/2] qemu-img: Resolve relative backing paths in rebase,
Max Reitz <=