stream: Allow users to request only format driver names in backing file format

[mirror_qemu.git] / block / stream.c

diff --git a/block/stream.c b/block/stream.c
index 2781441191b2e289f7a9b8157afa176076c36879..7031eef12b63494df345bf4c7b6ec276ba359328 100644 (file)
--- a/block/stream.c
+++ b/block/stream.c
@@ -39,6 +39,7 @@ typedef struct StreamBlockJob {
     BlockDriverState *target_bs;
     BlockdevOnError on_error;
     char *backing_file_str;
+    bool backing_mask_protocol;
     bool bs_read_only;
 } StreamBlockJob;
 
@@ -53,8 +54,8 @@ static int coroutine_fn stream_populate(BlockBackend *blk,
 static int stream_prepare(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
-    BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
-    BlockDriverState *unfiltered_bs_cow = bdrv_cow_bs(unfiltered_bs);
+    BlockDriverState *unfiltered_bs;
+    BlockDriverState *unfiltered_bs_cow;
     BlockDriverState *base;
     BlockDriverState *unfiltered_base;
     Error *local_err = NULL;
@@ -62,6 +63,11 @@ static int stream_prepare(Job *job)
 
     GLOBAL_STATE_CODE();
 
+    bdrv_graph_rdlock_main_loop();
+    unfiltered_bs = bdrv_skip_filters(s->target_bs);
+    unfiltered_bs_cow = bdrv_cow_bs(unfiltered_bs);
+    bdrv_graph_rdunlock_main_loop();
+
     /* We should drop filter at this point, as filter hold the backing chain */
     bdrv_cor_filter_drop(s->cor_filter_bs);
     s->cor_filter_bs = NULL;
@@ -85,16 +91,23 @@ static int stream_prepare(Job *job)
     unfiltered_base = bdrv_skip_filters(base);
     bdrv_graph_rdunlock_main_loop();
 
-    if (bdrv_cow_child(unfiltered_bs)) {
+    if (unfiltered_bs_cow) {
         const char *base_id = NULL, *base_fmt = NULL;
         if (unfiltered_base) {
             base_id = s->backing_file_str ?: unfiltered_base->filename;
             if (unfiltered_base->drv) {
-                base_fmt = unfiltered_base->drv->format_name;
+                if (s->backing_mask_protocol &&
+                    unfiltered_base->drv->protocol_name) {
+                    base_fmt = "raw";
+                } else {
+                    base_fmt = unfiltered_base->drv->format_name;
+                }
             }
         }
 
+        bdrv_graph_wrlock();
         bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err);
+        bdrv_graph_wrunlock();
 
         /*
          * This call will do I/O, so the graph can change again from here on.
@@ -142,18 +155,19 @@ static void stream_clean(Job *job)
 static int coroutine_fn stream_run(Job *job, Error **errp)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
-    BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
+    BlockDriverState *unfiltered_bs;
     int64_t len;
     int64_t offset = 0;
     int error = 0;
     int64_t n = 0; /* bytes */
 
-    if (unfiltered_bs == s->base_overlay) {
-        /* Nothing to stream */
-        return 0;
-    }
-
     WITH_GRAPH_RDLOCK_GUARD() {
+        unfiltered_bs = bdrv_skip_filters(s->target_bs);
+        if (unfiltered_bs == s->base_overlay) {
+            /* Nothing to stream */
+            return 0;
+        }
+
         len = bdrv_co_getlength(s->target_bs);
         if (len < 0) {
             return len;
@@ -239,6 +253,7 @@ static const BlockJobDriver stream_job_driver = {
 
 void stream_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *base, const char *backing_file_str,
+                  bool backing_mask_protocol,
                   BlockDriverState *bottom,
                   int creation_flags, int64_t speed,
                   BlockdevOnError on_error,
@@ -260,6 +275,8 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     assert(!(base && bottom));
     assert(!(backing_file_str && bottom));
 
+    bdrv_graph_rdlock_main_loop();
+
     if (bottom) {
         /*
          * New simple interface. The code is written in terms of old interface
@@ -272,13 +289,11 @@ void stream_start(const char *job_id, BlockDriverState *bs,
         assert(!bottom->drv->is_filter);
         base_overlay = above_base = bottom;
     } else {
-        GRAPH_RDLOCK_GUARD_MAINLOOP();
-
         base_overlay = bdrv_find_overlay(bs, base);
         if (!base_overlay) {
             error_setg(errp, "'%s' is not in the backing chain of '%s'",
                        base->node_name, bs->node_name);
-            return;
+            goto out_rdlock;
         }
 
         /*
@@ -300,7 +315,7 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     if (bs_read_only) {
         /* Hold the chain during reopen */
         if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
-            return;
+            goto out_rdlock;
         }
 
         ret = bdrv_reopen_set_read_only(bs, false, errp);
@@ -309,10 +324,12 @@ void stream_start(const char *job_id, BlockDriverState *bs,
         bdrv_unfreeze_backing_chain(bs, above_base);
 
         if (ret < 0) {
-            return;
+            goto out_rdlock;
         }
     }
 
+    bdrv_graph_rdunlock_main_loop();
+
     opts = qdict_new();
 
     qdict_put_str(opts, "driver", "copy-on-read");
@@ -356,7 +373,7 @@ void stream_start(const char *job_id, BlockDriverState *bs,
      * already have our own plans. Also don't allow resize as the image size is
      * queried only at the job start and then cached.
      */
-    bdrv_graph_wrlock(bs);
+    bdrv_graph_wrlock();
     if (block_job_add_bdrv(&s->common, "active node", bs, 0,
                            basic_flags | BLK_PERM_WRITE, errp)) {
         bdrv_graph_wrunlock();
@@ -388,6 +405,7 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     s->base_overlay = base_overlay;
     s->above_base = above_base;
     s->backing_file_str = g_strdup(backing_file_str);
+    s->backing_mask_protocol = backing_mask_protocol;
     s->cor_filter_bs = cor_filter_bs;
     s->target_bs = bs;
     s->bs_read_only = bs_read_only;
@@ -407,4 +425,8 @@ fail:
     if (bs_read_only) {
         bdrv_reopen_set_read_only(bs, true, NULL);
     }
+    return;
+
+out_rdlock:
+    bdrv_graph_rdunlock_main_loop();
 }