On 05/10/2014 10:35 AM, Jun Li wrote: > From: Jun Li <junm...@gmail.com>
I see three different "[PATCH v3]" mails with this subject. To make sure we are reviewing the right version, it might help to bump to version 4. > > This patch fixed the following bug: > https://bugzilla.redhat.com/show_bug.cgi?id=1084302 . > > path_combine can not calculate the correct full path name for backing_file. > Such as: > create a snapshot chain: > sn2->sn1->$BASE_IMG > backing file is : /home/wookpecker/img.qcow2 > sn1 : /home/woodpecker/tmp/sn1 > sn2 : /home/woodpecker/tmp/sn2 > when create sn2, path_combine can not got a correct path for $BASE_IMG. I'm having a hard time parsing that. We usually represent backing chains with the base image on the left: base <- sn1 Can you show the output of 'qemu-img info --backing-chain /home/woodpecker/tmp/sn2' to make it a bit more obvious what your setup is? What command are you issuing that triggers a path_combine that is getting the wrong result? > > In this patch, will check the backing_filename is a symlink or not firstly, > then return the full(absolute) path via realpath. This feels fishy to me, and liable to do the wrong thing. I need more context on how to reproduce the issue you are attempting to fix before I can even decide if your fix is the right approach. > > Signed-off-by: Jun Li <junm...@gmail.com> > --- > block.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/block.c b/block.c > index b749d31..6674719 100644 > --- a/block.c > +++ b/block.c > @@ -304,10 +304,26 @@ void path_combine(char *dest, int dest_size, > > void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t > sz) > { > + struct stat sb; > + char *linkname; > + > if (bs->backing_file[0] == '\0' || path_has_protocol(bs->backing_file)) { > pstrcpy(dest, sz, bs->backing_file); > } else { > - path_combine(dest, sz, bs->filename, bs->backing_file); > + if (lstat(bs->backing_file, &sb) == -1) { > + perror("lstat"); > + exit(EXIT_FAILURE); > + } > + > + /* Check linkname is a link or not */ > + if (S_ISLNK(sb.st_mode)) { > + linkname = malloc(sb.st_size + 1); > + readlink(bs->backing_file, linkname, sb.st_size + 1); > + linkname[sb.st_size] = '\0'; > + realpath(linkname, dest); > + } else { > + realpath(bs->backing_file, dest); > + } Why are you tweaking just this caller, instead of path_combine() to affect all other callers? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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