Re: [Qemu-devel] qcow2 corrupted image, no error from qemu-img check

[nicolas prochazka]

hello

test with qemu-img from git tree with your patch for log : 

DEV-10.98.98.1:~# /tmp/qemu-img convert -O qed /mnt/disks/export/images/vm_import  /mnt/disks/export-ns/test

qemu-img: error while reading bs_i 0 sector_num 5406720 bs_offset 0 n 4096: Input/output error

Regards,

Nicolas

2011/10/3 Stefan Hajnoczi <address@hidden>

On Mon, Oct 3, 2011 at 2:01 PM, nicolas prochazka
<address@hidden> wrote:
> sorry to bother you, i send dump of two qemu-io command .
> What can I do with this result ?

The qemu-io -c read command was successful.  This means that the I/O
error was triggered by the specific request that qemu-img convert
issued, not a general problem with the image file.  It also means the
image itself may not be corrupted at all - this could just be a bug in
the qemu-img convert code.

Thanks for collecting the qemu-io -c map output.  The image file has
clusters allocated around the offset where your I/O error was
reported.  There's nothing unusal in this output:

[              2768175104]      128/ 36536448 sectors     allocated at
offset 2.578 GiB (1)
[              **2768240640**]      128/ 36536320 sectors
allocated at offset 2.578 GiB (1)
[              2768306176]      128/ 36536192 sectors     allocated at
offset 2.578 GiB (1)
[              2768371712]      128/ 36536064 sectors     allocated at
offset 2.578 GiB (1)
[              2768437248]      128/ 36535936 sectors     allocated at
offset 2.578 GiB (1)
[              2768502784]      128/ 36535808 sectors     allocated at
offset 2.578 GiB (1)
[              2768568320]      128/ 36535680 sectors     allocated at
offset 2.578 GiB (1)

> cp is working well but no qemu-img

Good, so this looks like a QEMU bug.

Try enhancing the error output like this:

diff --git a/qemu-img.c b/qemu-img.c
index 6a39731..c300164 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1010,8 +1010,9 @@ static int img_convert(int argc, char **argv)

            ret = bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n);
            if (ret < 0) {
-                error_report("error while reading sector %" PRId64 ": %s",
-                             sector_num - bs_offset, strerror(-ret));
+                error_report("error while reading bs_i %d sector_num %"
+                             PRId64 " bs_offset %" PRId64 " n %d: %s",
+                             bs_i, sector_num, bs_offset, n, strerror(-ret));
                goto out;
            }
            /* NOTE: at the same time we convert, we do not write zero

Perhaps one of the arguments is out of range.  Are you comfortable
applying this patch to qemu-img.c, rebuilding, and running the
qemu-img convert again?

Stefan