[libvirt] [PATCH 4/5] conf: track more fields in backing chain metadata

[Eric Blake]

The current use of virStorageFileMetadata is awkward; to learn
some of the information about a child node, you have to read
fields in the parent node.  This does not lend itself well to
modifying backing chains (whether inserting a new node in the
chain, or consolidating existing nodes); better would be to
learn about a child node directly in that node.  This patch
sets up some new fields which contain redundant information,
although not necessarily in the final desired state for the
new fields (see the next patch for actual tests of what is there
now).  Then later patches will do any refactoring necessary to
get the fields to their desired states, and update clients to
get the information from the new fields, so we can finally
delete the fields that are tracking information about the wrong
node.

* src/util/virstoragefile.h (_virStorageFileMetadata): Add
path, canonName, relDir, type, and format fields.  Reorder
existing fields, and add lots of comments.
* src/util/virstoragefile.c (virStorageFileFreeMetadata): Clean
new fields.
(virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataFromFDInternal): Start populating new
fields.

Signed-off-by: Eric Blake <eblake at redhat.com>
---
 src/util/virstoragefile.c | 30 ++++++++++++++++++++++++++++--
 src/util/virstoragefile.h | 35 ++++++++++++++++++++++++++++++-----
 2 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 0e1461d..d741fb7 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -798,6 +798,10 @@ virStorageFileGetMetadataInternal(const char *path,

     if (VIR_ALLOC(meta) < 0)
         return NULL;
+    if (VIR_STRDUP(meta->path, path) < 0)
+        goto cleanup;
+    if (VIR_STRDUP(meta->relDir, directory) < 0)
+        goto cleanup;

     if (format == VIR_STORAGE_FILE_AUTO)
         format = virStorageFileProbeFormatFromBuf(path, buf, len);
@@ -808,6 +812,7 @@ virStorageFileGetMetadataInternal(const char *path,
                              format);
         goto cleanup;
     }
+    meta->format = format;

     /* XXX we should consider moving virStorageBackendUpdateVolInfo
      * code into this method, for non-magic files
@@ -1013,9 +1018,20 @@ virStorageFileGetMetadataFromFDInternal(const char *path,
         return NULL;
     }

-    /* No header to probe for directories, but also no backing file */
     if (S_ISDIR(sb.st_mode)) {
-        ignore_value(VIR_ALLOC(ret));
+        /* No header to probe for directories, but also no backing
+         * file; therefore, no inclusion loop is possible, and we
+         * don't need canonName or relDir.  */
+        if (VIR_ALLOC(ret) < 0)
+            goto cleanup;
+        if (VIR_STRDUP(ret->path, path) < 0) {
+            virStorageFileFreeMetadata(ret);
+            ret = NULL;
+            goto cleanup;
+        }
+        ret->type = VIR_STORAGE_TYPE_DIR;
+        ret->format = format > VIR_STORAGE_FILE_NONE ? format
+            : VIR_STORAGE_FILE_DIR;
         goto cleanup;
     }

@@ -1030,6 +1046,12 @@ virStorageFileGetMetadataFromFDInternal(const char *path,
     }

     ret = virStorageFileGetMetadataInternal(path, buf, len, directory, format);
+    if (ret) {
+        if (S_ISREG(sb.st_mode))
+            ret->type = VIR_STORAGE_TYPE_FILE;
+        else if (S_ISBLK(sb.st_mode))
+            ret->type = VIR_STORAGE_TYPE_BLOCK;
+    }
  cleanup:
     VIR_FREE(buf);
     return ret;
@@ -1205,6 +1227,10 @@ virStorageFileFreeMetadata(virStorageFileMetadata *meta)
     if (!meta)
         return;

+    VIR_FREE(meta->path);
+    VIR_FREE(meta->canonName);
+    VIR_FREE(meta->relDir);
+
     virStorageFileFreeMetadata(meta->backingMeta);
     VIR_FREE(meta->backingStore);
     VIR_FREE(meta->backingStoreRaw);
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index 3807285..a284e37 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -112,17 +112,42 @@ struct _virStorageTimestamps {
 typedef struct _virStorageFileMetadata virStorageFileMetadata;
 typedef virStorageFileMetadata *virStorageFileMetadataPtr;
 struct _virStorageFileMetadata {
-    char *backingStore; /* Canonical name (absolute file, or protocol) */
-    char *backingStoreRaw; /* If file, original name, possibly relative */
-    char *directory; /* The directory containing basename of backingStoreRaw */
-    int backingStoreFormat; /* enum virStorageFileFormat */
-    bool backingStoreIsFile;
+    /* Name of this file as spelled by the user (top level) or
+     * metadata of the parent (if this is a backing store).  */
+    char *path;
+    /* Canonical name of this file, used to detect loops in the
+     * backing store chain.  */
+    char *canonName;
+    /* Directory to start from if backingStoreRaw is a relative file
+     * name */
+    char *relDir;
+    /* Name of the backing store recorded in metadata of the parent */
+    char *backingStoreRaw;
+
+    /* Backing chain.  backingMeta->origName should match
+     * backingStoreRaw; but the fields are duplicated in the common
+     * case to make it possible to detect missing backing files, as
+     * follows: if backingStoreRaw is NULL, this should be NULL.  If
+     * this is NULL and backingStoreRaw is non-NULL, there was an
+     * error following the chain (such as missing file).  Otherwise,
+     * information about the backing store is here.  */
     virStorageFileMetadataPtr backingMeta;

+    /* Details about the current image */
+    int type; /* enum virStorageType */
+    int format; /* enum virStorageFileFormat */
     virStorageEncryptionPtr encryption;
     unsigned long long capacity;
     virBitmapPtr features; /* bits described by enum virStorageFileFeature */
     char *compat;
+
+    /* Fields I'm trying to delete, because it is confusing to have to
+     * query the parent metadata for details about the backing
+     * store.  */
+    char *backingStore; /* Canonical name (absolute file, or protocol). Should be same as backingMeta->canon */
+    char *directory; /* The directory containing basename of backingStoreRaw. Should be same as backingMeta->relDir */
+    int backingStoreFormat; /* enum virStorageFileFormat. Should be same as backingMeta->format */
+    bool backingStoreIsFile; /* Should be same as backingMeta->type < VIR_STORAGE_TYPE_NETWORK */
 };


-- 
1.9.0