block: Handle null backing link

Instead of converting all "backing": null instances into "backing": "",
handle a null value directly in bdrv_open_inherit().

This enables explicitly null backing links for json:{} filenames.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-7-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to() parameter order and qapi headers split]
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Max Reitz 2018-02-24 16:40:32 +01:00 committed by Eric Blake
parent 532fb53284
commit e59a0cf17b
4 changed files with 32 additions and 15 deletions

View file

@ -82,6 +82,26 @@ $QEMU_IO_PROG --cache $CACHEMODE \
$QEMU_IO -c 'read -P 42 0 512' "$TEST_IMG" | _filter_qemu_io
echo
echo "=== Testing correct handling of 'backing':null ==="
echo
_make_test_img -b "$TEST_IMG.base" $IMG_SIZE
# This should read 42
$QEMU_IO -c 'read -P 42 0 512' "$TEST_IMG" | _filter_qemu_io
# This should read 0
$QEMU_IO -c 'read -P 0 0 512' "json:{\
'driver': '$IMGFMT',
'file': {
'driver': 'file',
'filename': '$TEST_IMG'
},
'backing': null
}" | _filter_qemu_io
# Taken from test 071
echo
echo "=== Testing blkdebug ==="

View file

@ -19,6 +19,14 @@ Pattern verification failed at offset 0, 512 bytes
read 512/512 bytes at offset 0
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
=== Testing correct handling of 'backing':null ===
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
read 512/512 bytes at offset 0
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 512/512 bytes at offset 0
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
=== Testing blkdebug ===
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864