[PATCH 5/6] storage: Improve error message when traversing backing chains

[Peter Krempa <pkrempa@xxxxxxxxxx>]

Report also the name of the parent file and uid/gid used to access it to
help debugging broken storage configurations.
---
 src/storage/storage_driver.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index 1963bd6..87f3c1c 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -2781,6 +2781,7 @@ virStorageFileChown(virStorageSourcePtr src,
 /* Recursive workhorse for virStorageFileGetMetadata.  */
 static int
 virStorageFileGetMetadataRecurse(virStorageSourcePtr src,
+                                 virStorageSourcePtr parent,
                                  uid_t uid, gid_t gid,
                                  bool allow_probe,
                                  bool fail,
@@ -2805,9 +2806,18 @@ virStorageFileGetMetadataRecurse(virStorageSourcePtr src,
         return -1;

     if (virStorageFileAccess(src, F_OK) < 0) {
-        virReportSystemError(errno,
-                             _("Cannot access backing file %s"),
-                             src->path);
+        if (src == parent) {
+            virReportSystemError(errno,
+                                 _("Cannot access storage file '%s' "
+                                   "(as uid:%d, gid:%d)"),
+                                 src->path, (int)uid, (int)gid);
+        } else {
+            virReportSystemError(errno,
+                                 _("Cannot access backing file '%s' "
+                                   "of storage file '%s' (as uid:%d, gid:%d)"),
+                                 src->path, parent->path, (int)uid, (int)gid);
+        }
+
         goto cleanup;
     }

@@ -2848,7 +2858,7 @@ virStorageFileGetMetadataRecurse(virStorageSourcePtr src,
     else
         backingStore->format = backingFormat;

-    if ((ret = virStorageFileGetMetadataRecurse(backingStore,
+    if ((ret = virStorageFileGetMetadataRecurse(backingStore, parent,
                                                 uid, gid, allow_probe, fail,
                                                 cycle)) < 0) {
         if (fail)
@@ -2910,7 +2920,7 @@ virStorageFileGetMetadata(virStorageSourcePtr src,
     if (src->format <= VIR_STORAGE_FILE_NONE)
         src->format = allow_probe ? VIR_STORAGE_FILE_AUTO : VIR_STORAGE_FILE_RAW;

-    ret = virStorageFileGetMetadataRecurse(src, uid, gid,
+    ret = virStorageFileGetMetadataRecurse(src, src, uid, gid,
                                            allow_probe, fail, cycle);

     virHashFree(cycle);
-- 
2.1.0

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