[PATCH 10/20] block-gen: assert that {bdrv/blk}_co_truncate is always called with graph rdlock taken

[Emanuele Giuseppe Esposito]

This function, in addition to be called by a generated_co_wrapper,
is also called by the blk_* API.
The strategy is to always take the lock at the function called
when the coroutine is created, to avoid recursive locking.

Protecting bdrv_co_truncate() implies that
BlockDriver->bdrv_co_truncate() is always called with
graph rdlock taken.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/block-backend.c            | 1 +
 block/io.c                       | 1 +
 include/block/block_int-common.h | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 333d50fb3f..0686cd6942 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2370,6 +2370,7 @@ int coroutine_fn blk_co_truncate(BlockBackend *blk, 
int64_t offset, bool exact,
                                  Error **errp)
 {
     IO_OR_GS_CODE();
+    GRAPH_RDLOCK_GUARD();
     if (!blk_is_available(blk)) {
         error_setg(errp, "No medium inserted");
         return -ENOMEDIUM;
diff --git a/block/io.c b/block/io.c
index 9bcb19e5ee..ac12725fb2 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3295,6 +3295,7 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, 
int64_t offset, bool exact,
     int64_t old_size, new_bytes;
     int ret;
     IO_CODE();
+    assert_bdrv_graph_readable();
 
     /* if bs->drv == NULL, bs is closed, so there's nothing to do here */
     if (!drv) {
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index fd9f40a815..d666b0c441 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -681,6 +681,8 @@ struct BlockDriver {
      *
      * If @exact is true and this function fails but would succeed
      * with @exact = false, it should return -ENOTSUP.
+     *
+     * Called with graph rdlock held.
      */
     int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
                                          bool exact, PreallocMode prealloc,
-- 
2.31.1