Hello,
There is no change in userland tools after resizing qcow2 image except
file utility.
For example when resize qcow2 image, the "file" utility is detectable
increased size.
However, the "ls", “stat”, and “du” utility still don't know how many
change size of image is changed.
The following patch enables to let userland tools - ls, du, stat -
know and apply changed size after resizing qcow2 image created by the
qemu-img tool.
Currently, “file” utility can only know without this patch.
In addtion, "file" utility sometimes don't know qcow2 image format's
version as follows.
$ file 100G.qcow2
100G.qcow2: QEMU QCOW Image (Unknown)
So, user can't have any information about qcow2 image size.
======================
Signed-off-by: Taeha Kim <kthg...@gmail.com>
diff --git a/block.c b/block.c
index d088ee0..93427f8 100644
--- a/block.c
+++ b/block.c
@@ -2529,6 +2529,9 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset)
if (bs->blk) {
blk_dev_resize_cb(bs->blk);
}
+ if (ret == 0) {
+ ret = truncate(bs->filename, offset);
+ }
}
return ret;
}
=====================
$ ./qemu/qemu-img --version
qemu-img version 2.3.91, Copyright (c) 2004-2008 Fabrice Bellard
The how-to-reproduce is as follows with three reproduction.
First let’s say that we create a qcow2 image using qemu-img tool as
follows. There is still no problem.
$ ./qemu/qemu-img create -f qcow2 -o preallocation=metadata 100G.qcow2 100G
Formatting '100G.qcow2', fmt=qcow2 size=107374182400 encryption=off
cluster_size=65536 preallocation='metadata' lazy_refcounts=off
refcount_bits=16
$ ./qemu/qemu-img check 100G.qcow2
No errors were found on the image.
1638400/1638400 = 100.00% allocated, 0.00% fragmented, 0.00% compressed clusters
Image end offset: 107390828544
$ ls -l 100G.qcow2
-rw-r--r--. 1 devjames devjames 107390828544 Jul 15 09:55 100G.qcow2
$ stat 100G.qcow2
File: ‘100G.qcow2’
Size: 107390828544 Blocks: 32408 IO Block: 4096 regular file
Device: fd00h/64768d Inode: 5778245 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/devjames) Gid: ( 1000/devjames)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2015-07-15 09:55:17.269620129 +0900
Modify: 2015-07-15 09:55:17.269620129 +0900
Change: 2015-07-15 09:55:17.269620129 +0900
Birth: -
$ du -bb 100G.qcow2
107390828544 100G.qcow2
$ file 100G.qcow2
100G.qcow2: QEMU QCOW Image (v3), 107374182400 bytes
But, from now on there is a problem.
Second let’s say we resize the qcow2 image size from 100G to 200G
using current qemu-img without the patch.
$ ./qemu/qemu-img resize 100G.qcow2 200G
Image resized.
$ ./qemu/qemu-img check 100G.qcow2
No errors were found on the image.
1638400/3276800 = 50.00% allocated, 0.00% fragmented, 0.00% compressed clusters
Image end offset: 107390894080
$ ls -l 100G.qcow2
-rw-r--r--. 1 devjames devjames 107390832128 Jul 15 10:02 100G.qcow2
$ stat 100G.qcow2
File: ‘100G.qcow2’
Size: 107390832128 Blocks: 32416 IO Block: 4096 regular file
Device: fd00h/64768d Inode: 5778245 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/devjames) Gid: ( 1000/devjames)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2015-07-15 10:02:04.842425479 +0900
Modify: 2015-07-15 10:02:04.854425682 +0900
Change: 2015-07-15 10:02:04.854425682 +0900
Birth: -
$ du -bb 100G.qcow2
107390832128 100G.qcow2
$ file 100G.qcow2
100G.qcow2: QEMU QCOW Image (v3), 214748364800 bytes
We can see that “ls”, “stat”, and “du” utilities don’t know change
size of qcow2 image except “file” one.
Thanks.
Third let’s say we resize the qcow2 image size from 100G to 200G using
qemu-img with the patch.
$ ./qemu/qemu-img resize 100G.qcow2 200G
Image resized.
$ ./qemu/qemu-img check 100G.qcow2
No errors were found on the image.
1638400/3276800 = 50.00% allocated, 0.00% fragmented, 0.00% compressed clusters
Image end offset: 107390894080
$ ls -l 100G.qcow2
-rw-r--r--. 1 devjames devjames 214748364800 Jul 15 10:08 100G.qcow2
$ stat 100G.qcow2
File: ‘100G.qcow2’
Size: 214748364800 Blocks: 32416 IO Block: 4096 regular file
Device: fd00h/64768d Inode: 5778245 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/devjames) Gid: ( 1000/devjames)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2015-07-15 10:04:37.595018501 +0900
Modify: 2015-07-15 10:08:01.622484709 +0900
Change: 2015-07-15 10:08:01.622484709 +0900
Birth: -
$ du -bb 100G.qcow2
14748364800 100G.qcow2
$ file 100G.qcow2
100G.qcow2: QEMU QCOW Image (v3), 214748364800 bytes
Now we can see above all four utilities know change size of qcow2 image.
So I made the patch above for the "qemu-img" tool so that "ls",
“stat”, and “du” utility can be applied increased size of the qcow2
image file.
I have created a VM using qcow2 image after patching using this patch.
The 100G.qcow2 has resized 200G is detected and available.
$ qemu-kvm -smp 4 -m 4096 100G.qcow2 -cdrom
../iso/Fedora-Live-Workstation-x86_64-21-5.iso
Thanks.
Sincerely yours,
Taeha Kim
Senior Engineer, Network Functions Virtualization Part, Samsung Electronics
