On 19.05.21 12:19, Thomas Huth wrote:
On 29/03/2021 09.25, Thomas Huth wrote:
Fixed-size VHD images don't have a header, only a footer. To be able
to still detect them right, support probing via the file name, too.
Without this change, images get detected as raw:
$ qemu-img create -f vpc -o subformat=fixed test.vhd 2G
Formatting 'test.vhd', fmt=vpc size=2147483648 subformat=fixed
$ qemu-img info test.vhd
image: test.vhd
file format: raw
virtual size: 2 GiB (2147992064 bytes)
disk size: 8 KiB
With this change:
$ qemu-img info test.vhd
image: test.vhd
file format: vpc
virtual size: 2 GiB (2147991552 bytes)
disk size: 8 KiB
Resolves: https://bugs.launchpad.net/qemu/+bug/1819182
Signed-off-by: Thomas Huth <th...@redhat.com>
---
I've marked the subject with RFC since I'm not quite sure whether this
is really a good idea... please let me know what you think about it...
block/vpc.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/block/vpc.c b/block/vpc.c
index 17a705b482..be561e4b39 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -191,8 +191,18 @@ static uint32_t vpc_checksum(void *p, size_t size)
static int vpc_probe(const uint8_t *buf, int buf_size, const char
*filename)
{
- if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8))
+ if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8)) {
return 100;
+ }
+
+ /* It could be a fixed-size image without header -> check
extension, too */
+ if (filename) {
+ int len = strlen(filename);
+ if (len > 4 && !strcasecmp(&filename[len - 4], ".vhd")) {
+ return 10;
+ }
+ }
+
return 0;
}
Ping!
Anybody any comments on this one?
Thomas
Sorry I’m replying so late, but honestly, it’s because I’m just a bit
afraid to respond. So, perhaps like others, I hoped someone else with a
stronger opinion would do it in my stead.
I understand this addresses a real problem, but OTOH probing by the file
extension intuitively seems like a bad solution to me. What’s the
problem with simply requiring the user to spcify the format in such a case?
I mean, I can’t think of a concrete problem with probing by the filename
extension. The worst that can happen is that a raw image is called
.vhd, we try to open it, and the vhd driver then says the image doesn’t
work. That could be a real problem, but, well, it would be kind of
deserved. (Unless the user really in good faith just thought .vhd would
be a nice extension for their raw virtual HDD image. Which, then again,
I couldn’t blame them for.)
Perhaps we could print a message if the extension matches that advises
the user to explicitly specify the format for such images?
Max
