block: Convert bdrv_co_preadv/pwritev to BdrvChild

This is the final patch for converting the common I/O path to take
a BdrvChild parameter instead of BlockDriverState.

The completion of this conversion means that all users that perform I/O
on an image need to actually hold a reference (in the form of BdrvChild,
possible as part of a BlockBackend) to that image. This also protects
against inconsistent use of BlockBackend vs. BlockDriverState functions
because direct use of a BlockDriverState isn't possible any more and
blk->root is private for block-backends.c.

In addition, we can now distinguish different users in the I/O path,
and the future op blockers work is going to add assertions based on
permissions stored in BdrvChild.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 4bc72658f9..a862f6577b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -760,7 +760,7 @@ int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
         throttle_group_co_io_limits_intercept(blk, bytes, false);
     }
 
-    return bdrv_co_preadv(blk_bs(blk), offset, bytes, qiov, flags);
+    return bdrv_co_preadv(blk->root, offset, bytes, qiov, flags);
 }
 
 int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
@@ -785,7 +785,7 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
         flags |= BDRV_REQ_FUA;
     }
 
-    return bdrv_co_pwritev(blk_bs(blk), offset, bytes, qiov, flags);
+    return bdrv_co_pwritev(blk->root, offset, bytes, qiov, flags);
 }
 
 typedef struct BlkRwCo {