On 10/10/2012 03:34 AM, Paolo Bonzini wrote: > 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 >
Doesn't block.c already rely on realpath(), in bdrv_open()? Why would this be any different using it here? >> + continue; >> + } >> + >> + if (strcmp(backing_file_full, filename_full) == 0) { >> + return curr_bs->backing_hd; >> } >> } >> >> >