+ }
+}
/*
- * Drops images above 'base' up to and including 'top', and sets the image
- * above 'top' to have base as its backing file.
+ * Drops images above 'base' up to and including 'top', and sets new 'base'
+ * as backing_hd of top_overlay (the image orignally has 'top' as backing
+ * file). top_overlay may be NULL if 'top' is active, no such update needed.
+ * Requires that the top_overlay to 'top' is opened r/w.
*
- * Requires that the overlay to 'top' is opened r/w, so that the backing file
- * information in 'bs' can be properly updated.
+ * 1) This will convert the following chain:
+ * ... <- base <- ... <- top <- overlay <-... <- active
*
- * E.g., this will convert the following chain:
- * bottom <- base <- intermediate <- top <- active
+ * to
+ *
+ * ... <- base <- overlay <- active
+ *
+ * 2) It is allowed for bottom==base, in which case it converts:
+ *
+ * ... <- base <- ... <- top <- overlay <- ... <- active
*
* to
*
- * bottom <- base <- active
+ * base <- overlay <- active
*
- * It is allowed for bottom==base, in which case it converts:
+ * 2) It also allows active==top, in which case it converts:
*
- * base <- intermediate <- top <- active
+ * ... <- base <- ... <- top (active)
*
* to
*
- * base <- active
+ * base == active == top, i.e. only base and lower remains: *top == *base when
+ * return.
+ *
+ * 3) If base==NULL, it will drop all the BDS below overlay and set its
+ * backing_hd to NULL. I.e.:
*
- * Error conditions:
- * if active == top, that is considered an error
+ * base(NULL) <- ... <- overlay <- ... <- active
*
+ * to
+ *
+ * overlay <- ... <- active
*/
int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
BlockDriverState *base)
{
- BlockDriverState *intermediate;
- BlockDriverState *base_bs = NULL;
- BlockDriverState *new_top_bs = NULL;
- BlkIntermediateStates *intermediate_state, *next;
- int ret = -EIO;
-
- QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete;
- QSIMPLEQ_INIT(&states_to_delete);
-
- if (!top->drv || !base->drv) {
- goto exit;
- }
+ BlockDriverState *drop_start, *overlay;
+ int ret = -EINVAL;
- new_top_bs = bdrv_find_overlay(active, top);
-
- if (new_top_bs == NULL) {
- /* we could not find the image above 'top', this is an error */
+ if (!top->drv || (base && !base->drv)) {
goto exit;
}
-
- /* special case of new_top_bs->backing_hd already pointing to base -
nothing
- * to do, no intermediate images */
- if (new_top_bs->backing_hd == base) {
+ if (top == base) {
ret = 0;
- goto exit;
- }
-
- intermediate = top;
-
- /* now we will go down through the list, and add each BDS we find
- * into our deletion queue, until we hit the 'base'
- */
- while (intermediate) {
- intermediate_state = g_malloc0(sizeof(BlkIntermediateStates));
- intermediate_state->bs = intermediate;
- QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry);
-
- if (intermediate->backing_hd == base) {
- base_bs = intermediate->backing_hd;
- break;
+ } else if (top == active) {
+ assert(base);
+ drop_start = active->backing_hd;
+ bdrv_swap(active, base);
+ base->backing_hd = NULL;
+ bdrv_unref(drop_start);
+ ret = 0;
+ } else {
+ /* If there's an overlay, its backing_hd points to top's BDS now,
+ * the top image is dropped but this BDS structure is kept and swapped
+ * with base, this way we keep the pointers valid after dropping top */
+ overlay = bdrv_find_overlay(active, top);
+ if (!overlay) {
+ goto exit;
+ }
+ if (base) {
+ ret = bdrv_change_backing_file(overlay, base->filename,
+ base->drv->format_name);
+ } else {
+ ret = bdrv_change_backing_file(overlay, "", "");