Il 10/10/2012 07:56, Jeff Cody ha scritto:
> Currently, bdrv_find_backing_image compares bs->backing_file with
> what is passed in as a backing_file name. Mismatches may occur,
> however, when bs->backing_file and backing_file are both not
> absolute or relative.
>
> Use path_combine() to make sure any relative backing filenames are
> relative to the current image filename being searched, and then use
> realpath() to make all comparisons based on absolute filenames.
>
> This also changes bdrv_find_backing_image to no longer be recursive,
> but iterative.
>
> Signed-off-by: Jeff Cody <jc...@redhat.com>
> ---
> block.c | 38 ++++++++++++++++++++++++++++++++------
> 1 file changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/block.c b/block.c
> index e95f613..641b8fa 100644
> --- a/block.c
> +++ b/block.c
> @@ -3123,18 +3123,44 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
> return -ENOTSUP;
> }
>
> +/* backing_file can either be relative, or absolute. If it is
> + * relative, it must be relative to the chain. So, passing in
> + * bs->filename from a BDS as backing_file should not be done,
> + * as that may be relative to the CWD rather than the chain. */
> BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
> const char *backing_file)
> {
> - if (!bs->drv) {
> + char filename_full[PATH_MAX];
> + char backing_file_full[PATH_MAX];
> + char filename_tmp[PATH_MAX];
> + BlockDriverState *curr_bs = NULL;
> +
> + if (!bs || !bs->drv) {
> return NULL;
> }
>
> - if (bs->backing_hd) {
> - if (strcmp(bs->backing_file, backing_file) == 0) {
> - return bs->backing_hd;
> - } else {
> - return bdrv_find_backing_image(bs->backing_hd, backing_file);
> + for (curr_bs = bs; curr_bs->backing_hd; curr_bs = curr_bs->backing_hd) {
> + /* If not an absolute filename path, make it relative to the current
> + * image's filename path */
> + path_combine(filename_tmp, sizeof(filename_tmp),
> + curr_bs->filename, backing_file);
> +
> + /* We are going to compare absolute pathnames */
> + if (!realpath(filename_tmp, filename_full)) {
> + continue;
> + }
> +
> + /* We need to make sure the backing filename we are comparing against
> + * is relative to the current image filename (or absolute) */
> + path_combine(filename_tmp, sizeof(filename_tmp),
> + curr_bs->filename, curr_bs->backing_file);
> +
> + if (!realpath(filename_tmp, backing_file_full)) {
Unfortunately realpath does not exist on Win32. But
http://lists.gnu.org/archive/html/grub-devel/2011-09/msg00034.html
suggests that there is a _fullpath and in fact already has all you need
to write a qemu_realpath function.
Paolo
> + continue;
> + }
> +
> + if (strcmp(backing_file_full, filename_full) == 0) {
> + return curr_bs->backing_hd;
> }
> }
>
>
