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[Bug 1808928] Re: Bitmap Extra data is not supported
From: |
John Snow |
Subject: |
[Bug 1808928] Re: Bitmap Extra data is not supported |
Date: |
Tue, 20 Apr 2021 17:17:06 -0000 |
my patches went in, ultimately, and my focus was since shifted
elsewhere. I just tried this by *manually* adding some extra data to a
bitmap by hand.
qemu-img create -f qcow2 foo.qcow2 64m
qemu-img bitmap --add foo.qcow2 mybitmap
This creates a bitmap extension header like this (starting at 0x1f8)
000001f0 00 00 00 00 00 00 00 00 23 85 28 75 00 00 00 18 |........#.(u....|
00000200 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 20 |............... |
00000210 00 00 00 00 00 05 00 00 |........ |
And a bitmap table that looks like this:
00050000 00 00 00 00 00 04 00 00 00 00 00 01 00 00 00 02 |................|
00050010 01 10 00 08 00 00 00 00 6d 79 62 69 74 6d 61 70 |........mybitmap|
I modified the bitmap table to add eight bytes of bad data:
00050000 00 00 00 00 00 04 00 00 00 00 00 01 00 00 00 02 |................|
00050010 01 10 00 08 00 00 00 08 62 61 64 64 61 74 61 21 |........baddata!|
00050020 6d 79 62 69 74 6d 61 70 |mybitmap|
And modified the header accordingly to add eight bytes to the table
(0x20f := 0x28):
000001f0 00 00 00 00 00 00 00 00 23 85 28 75 00 00 00 18 |........#.(u....|
00000200 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 28 |...............(|
00000210 00 00 00 00 00 05 00 00 |........ |
And in these cases, QEMU refuses to load or work with the image even
slightly, rendering you unable to remove it:
> ./qemu-img bitmap --remove foo.qcow2 mybitmap
qemu-img: Could not open 'foo.qcow2': Bitmap extra data is not supported
So, it's still an open issue.
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https://bugs.launchpad.net/bugs/1808928
Title:
Bitmap Extra data is not supported
Status in QEMU:
Incomplete
Bug description:
i am using dirty bitmaps and drive-backup. It works as aspected.
Lately, i encounter a disastrous error. There is not any information
about that situation. I cannot reach/open/attach/info or anything with
a qcow2 file.
virsh version
Compiled against library: libvirt 4.10.0
Using library: libvirt 4.10.0
Using API: QEMU 4.10.0
Running hypervisor: QEMU 2.12.0
"qemu-img: Could not open '/var/lib/libvirt/images/test.qcow2': Bitmap
extra data is not supported"
what is that mean? what should i do?
i cannot remove bitmap. i cannot open image or query.
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