block: Add Error parameter to bdrv_set_backing_hd()

Not all callers of bdrv_set_backing_hd() know for sure that attaching
the backing file will be allowed by the permission system. Return the
error from the function rather than aborting.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

4 files changed, 22 insertions, 10 deletions

diff --git a/block/commit.c b/block/commit.c
index 1e0f5318a4..22a0a4db98 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -121,7 +121,7 @@ static void commit_complete(BlockJob *job, void *opaque)
      * filter driver from the backing chain. Do this as the final step so that
      * the 'consistent read' permission can be granted.  */
     if (remove_commit_top_bs) {
-        bdrv_set_backing_hd(overlay_bs, top);
+        bdrv_set_backing_hd(overlay_bs, top, &error_abort);
     }
 }
 
@@ -316,8 +316,8 @@ void commit_start(const char *job_id, BlockDriverState *bs,
         goto fail;
     }
 
-    bdrv_set_backing_hd(commit_top_bs, top);
-    bdrv_set_backing_hd(overlay_bs, commit_top_bs);
+    bdrv_set_backing_hd(commit_top_bs, top, &error_abort);
+    bdrv_set_backing_hd(overlay_bs, commit_top_bs, &error_abort);
 
     s->commit_top_bs = commit_top_bs;
     bdrv_unref(commit_top_bs);
@@ -390,7 +390,7 @@ fail:
         blk_unref(s->top);
     }
     if (commit_top_bs) {
-        bdrv_set_backing_hd(overlay_bs, top);
+        bdrv_set_backing_hd(overlay_bs, top, &error_abort);
     }
     block_job_unref(&s->common);
 }
@@ -451,8 +451,8 @@ int bdrv_commit(BlockDriverState *bs)
         goto ro_cleanup;
     }
 
-    bdrv_set_backing_hd(commit_top_bs, backing_file_bs);
-    bdrv_set_backing_hd(bs, commit_top_bs);
+    bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);
+    bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);
 
     ret = blk_insert_bs(backing, backing_file_bs, &local_err);
     if (ret < 0) {
@@ -532,7 +532,7 @@ ro_cleanup:
 
     blk_unref(backing);
     if (backing_file_bs) {
-        bdrv_set_backing_hd(bs, backing_file_bs);
+        bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
     }
     bdrv_unref(commit_top_bs);
     blk_unref(src);
diff --git a/block/mirror.c b/block/mirror.c
index 869212daac..8497e0db83 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -503,6 +503,7 @@ static void mirror_exit(BlockJob *job, void *opaque)
     BlockDriverState *src = s->source;
     BlockDriverState *target_bs = blk_bs(s->target);
     BlockDriverState *mirror_top_bs = s->mirror_top_bs;
+    Error *local_err = NULL;
 
     /* Make sure that the source BDS doesn't go away before we called
      * block_job_completed(). */
@@ -516,7 +517,11 @@ static void mirror_exit(BlockJob *job, void *opaque)
     if (s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
         BlockDriverState *backing = s->is_none_mode ? src : s->base;
         if (backing_bs(target_bs) != backing) {
-            bdrv_set_backing_hd(target_bs, backing);
+            bdrv_set_backing_hd(target_bs, backing, &local_err);
+            if (local_err) {
+                error_report_err(local_err);
+                data->ret = -EPERM;
+            }
         }
     }
 
diff --git a/block/stream.c b/block/stream.c
index b9c2f43c57..0113710845 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -68,6 +68,7 @@ static void stream_complete(BlockJob *job, void *opaque)
     StreamCompleteData *data = opaque;
     BlockDriverState *bs = blk_bs(job->blk);
     BlockDriverState *base = s->base;
+    Error *local_err = NULL;
 
     if (!block_job_is_cancelled(&s->common) && data->reached_end &&
         data->ret == 0) {
@@ -79,9 +80,15 @@ static void stream_complete(BlockJob *job, void *opaque)
             }
         }
         data->ret = bdrv_change_backing_file(bs, base_id, base_fmt);
-        bdrv_set_backing_hd(bs, base);
+        bdrv_set_backing_hd(bs, base, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            data->ret = -EPERM;
+            goto out;
+        }
     }
 
+out:
     /* Reopen the image back in read-only mode if necessary */
     if (s->bs_flags != bdrv_get_flags(bs)) {
         /* Give up write permissions before making it read-only */
diff --git a/block/vvfat.c b/block/vvfat.c
index 72b482cb1f..aa61c329e7 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -3041,7 +3041,7 @@ static int enable_write_target(BlockDriverState *bs, Error **errp)
                                    &error_abort);
     *(void**) backing->opaque = s;
 
-    bdrv_set_backing_hd(s->bs, backing);
+    bdrv_set_backing_hd(s->bs, backing, &error_abort);
     bdrv_unref(backing);
 
     return 0;