[v4,08/15] block: Use CAFs when working with backing chains

Commit Message

Andrey Shinkevich May 12, 2020, 4:50 p.m. UTC

From: Max Reitz <[e-mail]>

Use child access functions when iterating through backing chains so
filters do not break the chain.

Signed-off-by: Max Reitz <[e-mail]>
---
 block.c | 40 ++++++++++++++++++++++++++++------------
 1 file changed, 28 insertions(+), 12 deletions(-)

Patch

diff --git a/block.c b/block.c
index 459412e..69e9152 100644
--- a/block.c
+++ b/block.c
@@ -4593,7 +4593,8 @@  int bdrv_change_backing_file(BlockDriverState *bs,
 }
 
 /*
- * Finds the image layer in the chain that has 'bs' as its backing file.
+ * Finds the image layer in the chain that has 'bs' (or a filter on
+ * top of it) as its backing file.
  *
  * active is the current topmost image.
  *
@@ -4605,11 +4606,18 @@  int bdrv_change_backing_file(BlockDriverState *bs,
 BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
                                     BlockDriverState *bs)
 {
-    while (active && bs != backing_bs(active)) {
-        active = backing_bs(active);
+    bs = bdrv_skip_rw_filters(bs);
+    active = bdrv_skip_rw_filters(active);
+
+    while (active) {
+        BlockDriverState *next = bdrv_backing_chain_next(active);
+        if (bs == next) {
+            return active;
+        }
+        active = next;
     }
 
-    return active;
+    return NULL;
 }
 
 /* Given a BDS, searches for the base layer. */
@@ -4761,9 +4769,7 @@  int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base,
      * other intermediate nodes have been dropped.
      * If 'top' is an implicit node (e.g. "commit_top") we should skip
      * it because no one inherits from it. We use explicit_top for that. */
-    while (explicit_top && explicit_top->implicit) {
-        explicit_top = backing_bs(explicit_top);
-    }
+    explicit_top = bdrv_skip_implicit_filters(explicit_top);
     update_inherits_from = bdrv_inherits_from_recursive(base, explicit_top);
 
     /* success - we can delete the intermediate states, and link top->base */
@@ -5205,7 +5211,7 @@  BlockDriverState *bdrv_lookup_bs(const char *device,
 bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
 {
     while (top && top != base) {
-        top = backing_bs(top);
+        top = bdrv_filtered_bs(top);
     }
 
     return top != NULL;
@@ -5466,7 +5472,17 @@  BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
 
     is_protocol = path_has_protocol(backing_file);
 
-    for (curr_bs = bs; curr_bs->backing; curr_bs = curr_bs->backing->bs) {
+    /*
+     * Being largely a legacy function, skip any filters here
+     * (because filters do not have normal filenames, so they cannot
+     * match anyway; and allowing json:{} filenames is a bit out of
+     * scope).
+     */
+    for (curr_bs = bdrv_skip_rw_filters(bs);
+         bdrv_filtered_cow_child(curr_bs) != NULL;
+         curr_bs = bdrv_backing_chain_next(curr_bs))
+    {
+        BlockDriverState *bs_below = bdrv_backing_chain_next(curr_bs);
 
         /* If either of the filename paths is actually a protocol, then
          * compare unmodified paths; otherwise make paths relative */
@@ -5474,7 +5490,7 @@  BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
             char *backing_file_full_ret;
 
             if (strcmp(backing_file, curr_bs->backing_file) == 0) {
-                retval = curr_bs->backing->bs;
+                retval = bs_below;
                 break;
             }
             /* Also check against the full backing filename for the image */
@@ -5484,7 +5500,7 @@  BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
                 bool equal = strcmp(backing_file, backing_file_full_ret) == 0;
                 g_free(backing_file_full_ret);
                 if (equal) {
-                    retval = curr_bs->backing->bs;
+                    retval = bs_below;
                     break;
                 }
             }
@@ -5510,7 +5526,7 @@  BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
             g_free(filename_tmp);
 
             if (strcmp(backing_file_full, filename_full) == 0) {
-                retval = curr_bs->backing->bs;
+                retval = bs_below;
                 break;
             }
         }