[PATCH 12/20] block-gen: assert that bdrv_co_pwrite 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 elsewhere else.
The strategy is to always take the lock at the function called
when the coroutine is created, to avoid recursive locking.

By protecting brdv_co_pwrite, we also automatically protect
the following other generated_co_wrappers:
blk_co_pwrite
blk_co_pwritev
blk_co_pwritev_part
blk_co_pwrite_compressed
blk_co_pwrite_zeroes

Protecting bdrv_driver_pwritev_compressed() and bdrv_driver_pwritev_compressed()
implies that the following BlockDriver callbacks always called with graph rdlock
taken:
- bdrv_aio_pwritev
- bdrv_co_writev
- bdrv_co_pwritev
- bdrv_co_pwritev_part
- bdrv_co_pwritev_compressed
- bdrv_co_pwritev_compressed_part

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/block-backend.c            | 1 +
 block/block-copy.c               | 8 ++++++--
 block/io.c                       | 2 ++
 include/block/block_int-common.h | 6 ++++++
 include/block/block_int-io.h     | 1 +
 5 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 0686cd6942..d48ec3a2ac 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1363,6 +1363,7 @@ blk_co_do_pwritev_part(BlockBackend *blk, int64_t offset, 
int64_t bytes,
     IO_CODE();
 
     blk_wait_while_drained(blk);
+    GRAPH_RDLOCK_GUARD();
 
     /* Call blk_bs() only after waiting, the graph may have changed */
     bs = blk_bs(blk);
diff --git a/block/block-copy.c b/block/block-copy.c
index f33ab1d0b6..dabf461112 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -464,6 +464,8 @@ static coroutine_fn int block_copy_task_run(AioTaskPool 
*pool,
  * a full-size buffer or disabled if the copy_range attempt fails.  The output
  * value of @method should be used for subsequent tasks.
  * Returns 0 on success.
+ *
+ * Called with graph rdlock taken.
  */
 static int coroutine_fn block_copy_do_copy(BlockCopyState *s,
                                            int64_t offset, int64_t bytes,
@@ -554,8 +556,10 @@ static coroutine_fn int block_copy_task_entry(AioTask 
*task)
     BlockCopyMethod method = t->method;
     int ret;
 
-    ret = block_copy_do_copy(s, t->req.offset, t->req.bytes, &method,
-                             &error_is_read);
+    WITH_GRAPH_RDLOCK_GUARD() {
+        ret = block_copy_do_copy(s, t->req.offset, t->req.bytes, &method,
+                                 &error_is_read);
+    }
 
     WITH_QEMU_LOCK_GUARD(&s->lock) {
         if (s->method == t->method) {
diff --git a/block/io.c b/block/io.c
index ac12725fb2..9280fb9f38 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1012,6 +1012,7 @@ static int coroutine_fn 
bdrv_driver_pwritev(BlockDriverState *bs,
     unsigned int nb_sectors;
     QEMUIOVector local_qiov;
     int ret;
+    assert_bdrv_graph_readable();
 
     bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
 
@@ -1090,6 +1091,7 @@ bdrv_driver_pwritev_compressed(BlockDriverState *bs, 
int64_t offset,
     BlockDriver *drv = bs->drv;
     QEMUIOVector local_qiov;
     int ret;
+    assert_bdrv_graph_readable();
 
     bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
 
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index f285a6b8f7..d44f825d95 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -479,6 +479,7 @@ struct BlockDriver {
     BlockAIOCB *(*bdrv_aio_preadv)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
+    /* Called with graph rdlock taken. */
     BlockAIOCB *(*bdrv_aio_pwritev)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
@@ -515,6 +516,7 @@ struct BlockDriver {
         QEMUIOVector *qiov, size_t qiov_offset,
         BdrvRequestFlags flags);
 
+    /* Called with graph rdlock taken. */
     int coroutine_fn (*bdrv_co_writev)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
         int flags);
@@ -532,10 +534,12 @@ struct BlockDriver {
      * no larger than 'max_transfer'.
      *
      * The buffer in @qiov may point directly to guest memory.
+     * Called with graph rdlock taken.
      */
     int coroutine_fn (*bdrv_co_pwritev)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         BdrvRequestFlags flags);
+    /* Called with graph rdlock taken. */
     int coroutine_fn (*bdrv_co_pwritev_part)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset,
         BdrvRequestFlags flags);
@@ -693,8 +697,10 @@ struct BlockDriver {
     BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
                                       Error **errp);
 
+    /* Called with graph rdlock held. */
     int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov);
+    /* Called with graph rdlock held. */
     int coroutine_fn (*bdrv_co_pwritev_compressed_part)(BlockDriverState *bs,
         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
         size_t qiov_offset);
diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index 8bc061ebb8..ae88507d6a 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -69,6 +69,7 @@ static inline int coroutine_fn bdrv_co_pwrite(BdrvChild 
*child,
 {
     QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
     IO_CODE();
+    assert_bdrv_graph_readable();
 
     return bdrv_co_pwritev(child, offset, bytes, &qiov, flags);
 }
-- 
2.31.1