On 05/12/2014 11:15 PM, Eric Blake wrote:
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.
Yes, I have send v4 of this patch and changed the commit description.
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?
Sorry, this is the wrong commit description, please see it on v4. In
version 4, I describe it just as followings:
create a snapshot chain:
$BASE_IMG<-sn1<-sn2
backing file is : ./img.qcow2
sn1 : ./tmp/sn1
sn2 : ./tmp/sn2
So,
# /opt/qemu-git-arm/bin/qemu-img info --backing-chain ./tmp/sn2
image: ./tmp/sn2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./tmp/sn1 (actual path: /home/lijun/Work/tmp/sn1)
Format specific information:
compat: 1.1
lazy refcounts: false
image: /home/lijun/Work/tmp/sn1
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
backing file: ./img.qcow2 (actual path: /home/lijun/Work/img.qcow2)
Format specific information:
compat: 1.1
lazy refcounts: false
image: /home/lijun/Work/img.qcow2
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 196K
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false
------------------
Before this patch,
# qemu-img create -f qcow2 -b ./img.qcow2 ./tmp/sn1
# qemu-img create -f qcow2 -b ./tmp/sn1 ./tmp/sn2
qemu-img: Could not open './tmp/sn1': No such file or directory
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.
This patch fixed the following bug(*Bug 1084302*
<https://bugzilla.redhat.com/show_bug.cgi?id=1084302> -Should improve
error info when can't find backing file for snapshot):
https://bugzilla.redhat.com/show_bug.cgi?id=1084302
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?
I will check. Thx.
Best Regards,
Jun Li
