Places that use patterns like

    if (bs->drv->is_filter && bs->file) {
        ... something about bs->file->bs ...
    }

should be

    BlockDriverState *filtered = bdrv_filtered_rw_bs(bs);
    if (filtered) {
        ... something about @filtered ...
    }

instead.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block.c    | 23 +++++++++++++++--------
 block/io.c |  5 +++--
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index 029c809a8e..86b84bea21 100644
--- a/block.c
+++ b/block.c
@@ -556,11 +556,12 @@ int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp)
 int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
 {
     BlockDriver *drv = bs->drv;
+    BlockDriverState *filtered = bdrv_filtered_rw_bs(bs);
 
     if (drv && drv->bdrv_probe_blocksizes) {
         return drv->bdrv_probe_blocksizes(bs, bsz);
-    } else if (drv && drv->is_filter && bs->file) {
-        return bdrv_probe_blocksizes(bs->file->bs, bsz);
+    } else if (filtered) {
+        return bdrv_probe_blocksizes(filtered, bsz);
     }
 
     return -ENOTSUP;
@@ -575,11 +576,12 @@ int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
 {
     BlockDriver *drv = bs->drv;
+    BlockDriverState *filtered = bdrv_filtered_rw_bs(bs);
 
     if (drv && drv->bdrv_probe_geometry) {
         return drv->bdrv_probe_geometry(bs, geo);
-    } else if (drv && drv->is_filter && bs->file) {
-        return bdrv_probe_geometry(bs->file->bs, geo);
+    } else if (filtered) {
+        return bdrv_probe_geometry(filtered, geo);
     }
 
     return -ENOTSUP;
@@ -5084,6 +5086,8 @@ int bdrv_has_zero_init_1(BlockDriverState *bs)
 
 int bdrv_has_zero_init(BlockDriverState *bs)
 {
+    BlockDriverState *filtered;
+
     if (!bs->drv) {
         return 0;
     }
@@ -5096,8 +5100,10 @@ int bdrv_has_zero_init(BlockDriverState *bs)
     if (bs->drv->bdrv_has_zero_init) {
         return bs->drv->bdrv_has_zero_init(bs);
     }
-    if (bs->file && bs->drv->is_filter) {
-        return bdrv_has_zero_init(bs->file->bs);
+
+    filtered = bdrv_filtered_rw_bs(bs);
+    if (filtered) {
+        return bdrv_has_zero_init(filtered);
     }
 
     /* safe default */
@@ -5142,8 +5148,9 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
         return -ENOMEDIUM;
     }
     if (!drv->bdrv_get_info) {
-        if (bs->file && drv->is_filter) {
-            return bdrv_get_info(bs->file->bs, bdi);
+        BlockDriverState *filtered = bdrv_filtered_rw_bs(bs);
+        if (filtered) {
+            return bdrv_get_info(filtered, bdi);
         }
         return -ENOTSUP;
     }
diff --git a/block/io.c b/block/io.c
index 06305c6ea6..4d6cf4b3c2 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3186,8 +3186,9 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset,
     }
 
     if (!drv->bdrv_co_truncate) {
-        if (bs->file && drv->is_filter) {
-            ret = bdrv_co_truncate(bs->file, offset, prealloc, errp);
+        BdrvChild *filtered = bdrv_filtered_rw_child(bs);
+        if (filtered) {
+            ret = bdrv_co_truncate(filtered, offset, prealloc, errp);
             goto out;
         }
         error_setg(errp, "Image format driver does not support resize");
-- 
2.21.0