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block: JSON filenames and relative backing files

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When using a relative backing file name, qemu needs to know the
directory of the top image file. For JSON filenames, such a directory
cannot be easily determined (e.g. how do you determine the directory of
a qcow2 BDS directly on top of a quorum BDS?). Therefore, do not allow
relative filenames for the backing file of BDSs only having a JSON
filename.

Furthermore, BDS::exact_filename should be used whenever possible. If
BDS::filename is not equal to BDS::exact_filename, the former will
always be a JSON object.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2014-11-26 17:20:26 +01:00 • committed by Stefan Hajnoczi
parent 0a82855a1a
commit 9f07429e88
3 changed files with 31 additions and 9 deletions
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28
block.c
View file

@ -305,19 +305,28 @@ void path_combine(char *dest, int dest_size,
void bdrv_get_full_backing_filename_from_filename(const char *backed,
const char *backing,
char *dest, size_t sz)
char *dest, size_t sz,
Error **errp)
{
if (backing[0] == '\0' || path_has_protocol(backing)) {
if (backing[0] == '\0' || path_has_protocol(backing) ||
path_is_absolute(backing))
{
pstrcpy(dest, sz, backing);
} else if (backed[0] == '\0' || strstart(backed, "json:", NULL)) {
error_setg(errp, "Cannot use relative backing file names for '%s'",
backed);
} else {
path_combine(dest, sz, backed, backing);
}
}
void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz)
void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz,
Error **errp)
{
bdrv_get_full_backing_filename_from_filename(bs->filename, bs->backing_file,
dest, sz);
char *backed = bs->exact_filename[0] ? bs->exact_filename : bs->filename;
bdrv_get_full_backing_filename_from_filename(backed, bs->backing_file,
dest, sz, errp);
}
void bdrv_register(BlockDriver *bdrv)
@ -1225,7 +1234,14 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
QDECREF(options);
goto free_exit;
} else {
bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX);
bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX,
&local_err);
if (local_err) {
ret = -EINVAL;
error_propagate(errp, local_err);
QDECREF(options);
goto free_exit;
}
}
if (!bs->drv || !bs->drv->supports_backing) {