[PATCH] block: drop unused bdrv_co_drain() API

[Stefan Hajnoczi <stefanha@redhat.com>]

bdrv_co_drain() has not been used since commit 9a0cec664eef ("mirror:
use bdrv_drained_begin/bdrv_drained_end") in 2016. Remove it so there
are fewer drain scenarios to worry about.

Use bdrv_drained_begin()/bdrv_drained_end() instead. They are "mixed"
functions that can be called from coroutine context. Unlike
bdrv_co_drain(), these functions provide control of the length of the
drained section, which is usually the right thing.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/block/block-io.h |  1 -
 block/io.c               | 15 ---------------
 2 files changed, 16 deletions(-)

diff --git a/include/block/block-io.h b/include/block/block-io.h
index 62c84f0519..053a27141a 100644
--- a/include/block/block-io.h
+++ b/include/block/block-io.h
@@ -270,7 +270,6 @@ void bdrv_drained_end_no_poll(BlockDriverState *bs, int *drained_end_counter);
                    cond); })
 
 void bdrv_drain(BlockDriverState *bs);
-void coroutine_fn bdrv_co_drain(BlockDriverState *bs);
 
 int generated_co_wrapper
 bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
diff --git a/block/io.c b/block/io.c
index 789e6373d5..1e9bf09a49 100644
--- a/block/io.c
+++ b/block/io.c
@@ -588,21 +588,6 @@ void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent)
     BDRV_POLL_WHILE(child->bs, qatomic_read(&drained_end_counter) > 0);
 }
 
-/*
- * Wait for pending requests to complete on a single BlockDriverState subtree,
- * and suspend block driver's internal I/O until next request arrives.
- *
- * Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
- * AioContext.
- */
-void coroutine_fn bdrv_co_drain(BlockDriverState *bs)
-{
-    IO_OR_GS_CODE();
-    assert(qemu_in_coroutine());
-    bdrv_drained_begin(bs);
-    bdrv_drained_end(bs);
-}
-
 void bdrv_drain(BlockDriverState *bs)
 {
     IO_OR_GS_CODE();
-- 
2.36.1