Re: Using json: in common.rc's TEST_IMG

[Hanna Czenczek <hreitz@redhat.com>]

On 31.05.23 21:09, Stefan Hajnoczi wrote:
> Another issue is that 145 uses $TEST_IMG as follows:
>
>    SYSEMU_DRIVE_ARG=if=none,file="$TEST_IMG",driver=$IMGFMT
>
> That doesn't work when json: contains a comma, since commas need to be
> doubled up to escape them. This fails:
>
>    $ qemu-system-x86_64 -drive
> 'if=none,file=json:{"driver":"io_uring","filename":"test.img"}'
>    qemu-system-x86_64: -drive
> if=none,file=json:{"driver":"io_uring","filename":"test.img"}:
> warning: short-form boolean option '"filename":"test.img"}' deprecated
>    Please use "filename":"test.img"}=on instead
>
> This works:
>
>    qemu-system-x86_64 -drive
> 'if=none,file=json:{"driver":"io_uring",,"filename":"test.img"}'
>
> Maybe it's simply not possible to use TEST_IMG=json: in qemu-iotests?

Probably not as-is.  None of the tests has been written with that in 
mind, and many have been written at a time where TEST_IMG was basically 
always a plain filename.  We’ve had a lot of churn in the past e.g. to 
separate TEST_IMG_FILE out from TEST_IMG, and I suspect if you want 
json:{} to work, that would be even more churn.

Admittedly I don’t remember how it’s to be done, but looking at the code 
(common.rc starting from line 274), it seems clear what other protocols 
do: If $IMGOPTSSYNTAX is true, use a dotted-key-value syntax; and 
otherwise, make use of the protocol prefix.  Now, "io_uring:test.img" 
doesn’t work, because while bdrv_io_uring has .protocol_name set, it 
doesn’t implement .bdrv_parse_filename(). file-posix for example does 
(see raw_parse_filename()), and all it does is to strip the protocol prefix.

So I think you should be able to get the non-IMGOPTSSYNTAX case to work 
by adding a trivial .bdrv_parse_filename() implementation to each blkio 
driver, which just strips the protocol prefix, and then use 
"io_uring:$TEST_IMG_FILE".

Hanna

> The alternative is to always set IMGOPTSSYNTAX=true and then find the
> test cases that fail because they contain non-IMGOPTSSYNTAX commands.
>
> Stefan
>