block: bdrv_get_full_backing_filename's ret. val.

Make bdrv_get_full_backing_filename() return an allocated string instead
of placing the result in a caller-provided buffer.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20190201192935.18394-12-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

3 files changed, 20 insertions, 43 deletions

diff --git a/block.c b/block.c
index 466d7887cc..a2203f0cfe 100644
--- a/block.c
+++ b/block.c
@@ -338,28 +338,16 @@ char *bdrv_get_full_backing_filename_from_filename(const char *backed,
     }
 }
 
-void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz,
-                                    Error **errp)
+char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp)
 {
     char *backed;
-    char *full_name;
-    Error *local_error = NULL;
 
     bdrv_refresh_filename(bs);
 
     backed = bs->exact_filename[0] ? bs->exact_filename : bs->filename;
-
-    full_name = bdrv_get_full_backing_filename_from_filename(backed,
-                                                             bs->backing_file,
-                                                             &local_error);
-    if (full_name) {
-        pstrcpy(dest, sz, full_name);
-        g_free(full_name);
-    } else if (local_error) {
-        error_propagate(errp, local_error);
-    } else if (sz > 0) {
-        *dest = '\0';
-    }
+    return bdrv_get_full_backing_filename_from_filename(backed,
+                                                        bs->backing_file,
+                                                        errp);
 }
 
 void bdrv_register(BlockDriver *bdrv)
@@ -2387,7 +2375,7 @@ out:
 int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
                            const char *bdref_key, Error **errp)
 {
-    char *backing_filename = g_malloc0(PATH_MAX);
+    char *backing_filename = NULL;
     char *bdref_key_dot;
     const char *reference = NULL;
     int ret = 0;
@@ -2422,7 +2410,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
      */
     reference = qdict_get_try_str(parent_options, bdref_key);
     if (reference || qdict_haskey(options, "file.filename")) {
-        backing_filename[0] = '\0';
+        /* keep backing_filename NULL */
     } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
         qobject_unref(options);
         goto free_exit;
@@ -2437,8 +2425,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
             implicit_backing = !strcmp(bs->auto_backing_file, bs->backing_file);
         }
 
-        bdrv_get_full_backing_filename(bs, backing_filename, PATH_MAX,
-                                       &local_err);
+        backing_filename = bdrv_get_full_backing_filename(bs, &local_err);
         if (local_err) {
             ret = -EINVAL;
             error_propagate(errp, local_err);
@@ -2459,9 +2446,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
         qdict_put_str(options, "driver", bs->backing_format);
     }
 
-    backing_hd = bdrv_open_inherit(*backing_filename ? backing_filename : NULL,
-                                   reference, options, 0, bs, &child_backing,
-                                   errp);
+    backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
+                                   &child_backing, errp);
     if (!backing_hd) {
         bs->open_flags |= BDRV_O_NO_BACKING;
         error_prepend(errp, "Could not open backing file: ");
@@ -4648,7 +4634,6 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
     int is_protocol = 0;
     BlockDriverState *curr_bs = NULL;
     BlockDriverState *retval = NULL;
-    Error *local_error = NULL;
 
     if (!bs || !bs->drv || !backing_file) {
         return NULL;
@@ -4668,21 +4653,22 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
         /* If either of the filename paths is actually a protocol, then
          * compare unmodified paths; otherwise make paths relative */
         if (is_protocol || path_has_protocol(curr_bs->backing_file)) {
+            char *backing_file_full_ret;
+
             if (strcmp(backing_file, curr_bs->backing_file) == 0) {
                 retval = curr_bs->backing->bs;
                 break;
             }
             /* Also check against the full backing filename for the image */
-            bdrv_get_full_backing_filename(curr_bs, backing_file_full, PATH_MAX,
-                                           &local_error);
-            if (local_error == NULL) {
-                if (strcmp(backing_file, backing_file_full) == 0) {
+            backing_file_full_ret = bdrv_get_full_backing_filename(curr_bs,
+                                                                   NULL);
+            if (backing_file_full_ret) {
+                bool equal = strcmp(backing_file, backing_file_full_ret) == 0;
+                g_free(backing_file_full_ret);
+                if (equal) {
                     retval = curr_bs->backing->bs;
                     break;
                 }
-            } else {
-                error_free(local_error);
-                local_error = NULL;
             }
         } else {
             /* If not an absolute filename path, make it relative to the current
diff --git a/block/qapi.c b/block/qapi.c
index 4623de1d7b..6002a768f8 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -296,18 +296,10 @@ void bdrv_query_image_info(BlockDriverState *bs,
 
     backing_filename = bs->backing_file;
     if (backing_filename[0] != '\0') {
-        char *backing_filename2 = g_malloc0(PATH_MAX);
+        char *backing_filename2;
         info->backing_filename = g_strdup(backing_filename);
         info->has_backing_filename = true;
-        bdrv_get_full_backing_filename(bs, backing_filename2, PATH_MAX, &err);
-        if (err) {
-            /* Can't reconstruct the full backing filename, so we must omit
-             * this field and apply a Best Effort to this query. */
-            g_free(backing_filename2);
-            backing_filename2 = NULL;
-            error_free(err);
-            err = NULL;
-        }
+        backing_filename2 = bdrv_get_full_backing_filename(bs, NULL);
 
         /* Always report the full_backing_filename if present, even if it's the
          * same as backing_filename. That they are same is useful info. */
diff --git a/include/block/block.h b/include/block/block.h
index 5f1650304d..42cc38f598 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -487,8 +487,7 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
 
 void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
-void bdrv_get_full_backing_filename(BlockDriverState *bs,
-                                    char *dest, size_t sz, Error **errp);
+char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp);
 char *bdrv_get_full_backing_filename_from_filename(const char *backed,
                                                    const char *backing,
                                                    Error **errp);