[libvirt] [PATCH 2/4] qemu: report error if disk backing files doesn't exist

[Guannan Ren]

Adding virFileAccessibleAs() to check if the backing file described in
disk meta exist in real path. If not, report error. The uid and gid
arguments don't take effect on F_OK mode for access, so use gid and gid
of current process.

---
 src/util/virstoragefile.c | 23 +++++++++++++++--------
 tests/virstoragetest.c    | 16 ++++++++--------
 2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index cb6df91..b678eb8 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -572,6 +572,13 @@ virFindBackingFile(const char *start, bool start_is_dir, const char *path,
         goto cleanup;
     }
 
+    if (virFileAccessibleAs(combined, F_OK, getuid(), getgid()) < 0) {
+        virReportSystemError(errno,
+                             _("Backing file '%s' does not exist"),
+                             combined);
+        goto cleanup;
+    }
+
     if (!(*canonical = canonicalize_file_name(combined))) {
         virReportSystemError(errno,
                              _("Can't canonicalize path '%s'"), path);
@@ -857,14 +864,10 @@ virStorageFileGetMetadataInternal(const char *path,
                                        !!directory, backing,
                                        &meta->directory,
                                        &meta->backingStore) < 0) {
-                    /* the backing file is (currently) unavailable, treat this
-                     * file as standalone:
-                     * backingStoreRaw is kept to mark broken image chains */
-                    meta->backingStoreIsFile = false;
-                    backingFormat = VIR_STORAGE_FILE_NONE;
-                    VIR_WARN("Backing file '%s' of image '%s' is missing.",
-                             meta->backingStoreRaw, path);
-
+                    VIR_FREE(backing);
+                    VIR_ERROR(_("Backing file '%s' of image '%s' is missing."),
+                              meta->backingStoreRaw, path);
+                    goto cleanup;
                 }
             }
             VIR_FREE(backing);
@@ -1047,6 +1050,10 @@ virStorageFileGetMetadataRecurse(const char *path, const char *directory,
                                                             uid, gid,
                                                             allow_probe,
                                                             cycle);
+        if (!ret->backingMeta) {
+            virStorageFileFreeMetadata(ret);
+            ret = NULL;
+        }
     }
 
     return ret;
diff --git a/tests/virstoragetest.c b/tests/virstoragetest.c
index a3c59ef..030f81b 100644
--- a/tests/virstoragetest.c
+++ b/tests/virstoragetest.c
@@ -480,10 +480,10 @@ mymain(void)
     /* Qcow2 file with missing backing file but specified type */
     const testFileData chain9[] = { qcow2_bogus };
     TEST_CHAIN(9, "qcow2", absqcow2, VIR_STORAGE_FILE_QCOW2,
-               chain9, EXP_WARN,
-               chain9, ALLOW_PROBE | EXP_WARN,
-               chain9, EXP_WARN,
-               chain9, ALLOW_PROBE | EXP_WARN);
+               chain9, EXP_FAIL,
+               chain9, ALLOW_PROBE | EXP_FAIL,
+               chain9, EXP_FAIL,
+               chain9, ALLOW_PROBE | EXP_FAIL);
 
     /* Rewrite qcow2 to a missing backing file, without backing type */
     virCommandFree(cmd);
@@ -495,10 +495,10 @@ mymain(void)
     /* Qcow2 file with missing backing file and no specified type */
     const testFileData chain10[] = { qcow2_bogus };
     TEST_CHAIN(10, "qcow2", absqcow2, VIR_STORAGE_FILE_QCOW2,
-               chain10, EXP_WARN,
-               chain10, ALLOW_PROBE | EXP_WARN,
-               chain10, EXP_WARN,
-               chain10, ALLOW_PROBE | EXP_WARN);
+               chain10, EXP_FAIL,
+               chain10, ALLOW_PROBE | EXP_FAIL,
+               chain10, EXP_FAIL,
+               chain10, ALLOW_PROBE | EXP_FAIL);
 
     /* Rewrite qcow2 to use an nbd: protocol as backend */
     virCommandFree(cmd);
-- 
1.8.3.1