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-rw-r--r--include/block/block_int.h21
1 files changed, 16 insertions, 5 deletions
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8b9d769e14..38cad9d15c 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -847,11 +847,20 @@ struct BlockDriverState {
bool walking_aio_notifiers; /* to make removal during iteration safe */
char filename[PATH_MAX];
- char backing_file[PATH_MAX]; /* if non zero, the image is a diff of
- this file image */
- /* The backing filename indicated by the image header; if we ever
- * open this file, then this is replaced by the resulting BDS's
- * filename (i.e. after a bdrv_refresh_filename() run). */
+ /*
+ * If not empty, this image is a diff in relation to backing_file.
+ * Note that this is the name given in the image header and
+ * therefore may or may not be equal to .backing->bs->filename.
+ * If this field contains a relative path, it is to be resolved
+ * relatively to the overlay's location.
+ */
+ char backing_file[PATH_MAX];
+ /*
+ * The backing filename indicated by the image header. Contrary
+ * to backing_file, if we ever open this file, auto_backing_file
+ * is replaced by the resulting BDS's filename (i.e. after a
+ * bdrv_refresh_filename() run).
+ */
char auto_backing_file[PATH_MAX];
char backing_format[16]; /* if non-zero and backing_file exists */
@@ -1053,6 +1062,8 @@ BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
QDict *options);
+bool bdrv_backing_overridden(BlockDriverState *bs);
+
/**
* bdrv_add_before_write_notifier: