[PATCH v2 05/36] block: add bdrv_parent_try_set_aio_context

[Vladimir Sementsov-Ogievskiy]

We already have bdrv_parent_can_set_aio_context(). Add corresponding
bdrv_parent_set_aio_context_ignore() and
bdrv_parent_try_set_aio_context() and use them instead of open-coding.

Make bdrv_parent_try_set_aio_context() public, as it will be used in
further commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block.h |  2 ++
 block.c               | 51 +++++++++++++++++++++++++++++++++----------
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index ee3f5a6cca..550c5a7513 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -686,6 +686,8 @@ bool bdrv_child_can_set_aio_context(BdrvChild *c, 
AioContext *ctx,
                                     GSList **ignore, Error **errp);
 bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx,
                               GSList **ignore, Error **errp);
+int bdrv_parent_try_set_aio_context(BdrvChild *c, AioContext *ctx,
+                                    Error **errp);
 int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz);
 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
 
diff --git a/block.c b/block.c
index 916087ee1a..5d925c208d 100644
--- a/block.c
+++ b/block.c
@@ -81,6 +81,9 @@ static BlockDriverState *bdrv_open_inherit(const char 
*filename,
                                            BdrvChildRole child_role,
                                            Error **errp);
 
+static void bdrv_parent_set_aio_context_ignore(BdrvChild *c, AioContext *ctx,
+                                               GSList **ignore);
+
 /* If non-zero, use only whitelisted block drivers */
 static int use_bdrv_whitelist;
 
@@ -2655,17 +2658,12 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState 
*child_bs,
      * try moving the parent into the AioContext of child_bs instead. */
     if (bdrv_get_aio_context(child_bs) != ctx) {
         ret = bdrv_try_set_aio_context(child_bs, ctx, &local_err);
-        if (ret < 0 && child_class->can_set_aio_ctx) {
-            GSList *ignore = g_slist_prepend(NULL, child);
-            ctx = bdrv_get_aio_context(child_bs);
-            if (child_class->can_set_aio_ctx(child, ctx, &ignore, NULL)) {
-                error_free(local_err);
+        if (ret < 0) {
+            if (bdrv_parent_try_set_aio_context(child, ctx, NULL) == 0) {
                 ret = 0;
-                g_slist_free(ignore);
-                ignore = g_slist_prepend(NULL, child);
-                child_class->set_aio_ctx(child, ctx, &ignore);
+                error_free(local_err);
+                local_err = NULL;
             }
-            g_slist_free(ignore);
         }
         if (ret < 0) {
             error_propagate(errp, local_err);
@@ -6452,9 +6450,7 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
         if (g_slist_find(*ignore, child)) {
             continue;
         }
-        assert(child->klass->set_aio_ctx);
-        *ignore = g_slist_prepend(*ignore, child);
-        child->klass->set_aio_ctx(child, new_context, ignore);
+        bdrv_parent_set_aio_context_ignore(child, new_context, ignore);
     }
 
     bdrv_detach_aio_context(bs);
@@ -6511,6 +6507,37 @@ static bool bdrv_parent_can_set_aio_context(BdrvChild 
*c, AioContext *ctx,
     return true;
 }
 
+static void bdrv_parent_set_aio_context_ignore(BdrvChild *c, AioContext *ctx,
+                                               GSList **ignore)
+{
+    if (g_slist_find(*ignore, c)) {
+        return;
+    }
+    *ignore = g_slist_prepend(*ignore, c);
+
+    assert(c->klass->set_aio_ctx);
+    c->klass->set_aio_ctx(c, ctx, ignore);
+}
+
+int bdrv_parent_try_set_aio_context(BdrvChild *c, AioContext *ctx,
+                                    Error **errp)
+{
+    GSList *ignore = NULL;
+
+    if (!bdrv_parent_can_set_aio_context(c, ctx, &ignore, errp)) {
+        g_slist_free(ignore);
+        return -EPERM;
+    }
+
+    g_slist_free(ignore);
+    ignore = NULL;
+
+    bdrv_parent_set_aio_context_ignore(c, ctx, &ignore);
+    g_slist_free(ignore);
+
+    return 0;
+}
+
 bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
                                     GSList **ignore, Error **errp)
 {
-- 
2.21.3