snapshot: fixed bdrv_get_full_backing_filename can not get correct full_backing_filename

PATCH Superseded Jun Li 1 participant 1 message May 10, 2014

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Jun Li

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2014-05-10 16:33 UTC #0 lore raw

PATCH v3 1/1 snapshot: fixed bdrv_get_full_backing_filename can not get correct full_backing_filename

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.

In this patch, will check the backing_filename is a symlink or not firstly, then return the full(absolute) path via realpath.

Signed-off-by Jun Li <[email protected]>

---
 block.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

block.c +17 -1

index b749d31..6674719 100644
@@ -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);
+        }
     }
 }

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