block: Convert bdrv_io_plug() to co_wrapper

BlockDriver->bdrv_io_plug is categorized as IO callback, and it
currently doesn't run in a coroutine. We should let it take a graph
rdlock since the callback traverses the block nodes graph, which however
is only possible in a coroutine.

The only caller of this function is blk_io_plug(), therefore make
blk_io_plug() a co_wrapper, so that we're always running in a coroutine
where the lock can be taken.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230113204212.359076-3-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/block-backend.c

@@ -2315,13 +2315,13 @@ void blk_add_insert_bs_notifier(BlockBackend *blk, Notifier *notify)
     notifier_list_add(&blk->insert_bs_notifiers, notify);
 }
 
-void blk_io_plug(BlockBackend *blk)
+void coroutine_fn blk_co_io_plug(BlockBackend *blk)
 {
     BlockDriverState *bs = blk_bs(blk);
     IO_CODE();
 
     if (bs) {
-        bdrv_io_plug(bs);
+        bdrv_co_io_plug(bs);
     }
 }
 

block/file-posix.c

@@ -2132,7 +2132,7 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, int64_t offset,
     return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);
 }
 
-static void raw_aio_plug(BlockDriverState *bs)
+static void coroutine_fn raw_co_io_plug(BlockDriverState *bs)
 {
     BDRVRawState __attribute__((unused)) *s = bs->opaque;
 #ifdef CONFIG_LINUX_AIO
@@ -3317,7 +3317,7 @@ BlockDriver bdrv_file = {
     .bdrv_co_copy_range_from = raw_co_copy_range_from,
     .bdrv_co_copy_range_to  = raw_co_copy_range_to,
     .bdrv_refresh_limits = raw_refresh_limits,
-    .bdrv_io_plug = raw_aio_plug,
+    .bdrv_co_io_plug        = raw_co_io_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
 
@@ -3689,7 +3689,7 @@ static BlockDriver bdrv_host_device = {
     .bdrv_co_copy_range_from = raw_co_copy_range_from,
     .bdrv_co_copy_range_to  = raw_co_copy_range_to,
     .bdrv_refresh_limits = raw_refresh_limits,
-    .bdrv_io_plug = raw_aio_plug,
+    .bdrv_co_io_plug        = raw_co_io_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
 
@@ -3813,7 +3813,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
     .bdrv_refresh_limits = raw_refresh_limits,
-    .bdrv_io_plug = raw_aio_plug,
+    .bdrv_co_io_plug        = raw_co_io_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
 
@@ -3943,7 +3943,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
     .bdrv_refresh_limits = raw_refresh_limits,
-    .bdrv_io_plug = raw_aio_plug,
+    .bdrv_co_io_plug        = raw_co_io_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
 

block/io.c

@@ -3137,19 +3137,19 @@ void *qemu_try_blockalign0(BlockDriverState *bs, size_t size)
     return mem;
 }
 
-void bdrv_io_plug(BlockDriverState *bs)
+void coroutine_fn bdrv_co_io_plug(BlockDriverState *bs)
 {
     BdrvChild *child;
     IO_CODE();
 
     QLIST_FOREACH(child, &bs->children, next) {
-        bdrv_io_plug(child->bs);
+        bdrv_co_io_plug(child->bs);
     }
 
     if (qatomic_fetch_inc(&bs->io_plugged) == 0) {
         BlockDriver *drv = bs->drv;
-        if (drv && drv->bdrv_io_plug) {
+        if (drv && drv->bdrv_co_io_plug) {
-            drv->bdrv_io_plug(bs);
+            drv->bdrv_co_io_plug(bs);
         }
     }
 }

block/nvme.c

@@ -1567,7 +1567,7 @@ static void nvme_attach_aio_context(BlockDriverState *bs,
     }
 }
 
-static void nvme_aio_plug(BlockDriverState *bs)
+static void coroutine_fn nvme_co_io_plug(BlockDriverState *bs)
 {
     BDRVNVMeState *s = bs->opaque;
     assert(!s->plugged);
@@ -1664,7 +1664,7 @@ static BlockDriver bdrv_nvme = {
     .bdrv_detach_aio_context  = nvme_detach_aio_context,
     .bdrv_attach_aio_context  = nvme_attach_aio_context,
 
-    .bdrv_io_plug             = nvme_aio_plug,
+    .bdrv_co_io_plug          = nvme_co_io_plug,
     .bdrv_io_unplug           = nvme_aio_unplug,
 
     .bdrv_register_buf        = nvme_register_buf,

include/block/block-io.h

@@ -215,7 +215,8 @@ void coroutine_fn bdrv_co_leave(BlockDriverState *bs, AioContext *old_ctx);
 
 AioContext *child_of_bds_get_parent_aio_context(BdrvChild *c);
 
-void bdrv_io_plug(BlockDriverState *bs);
+void coroutine_fn bdrv_co_io_plug(BlockDriverState *bs);
+
 void bdrv_io_unplug(BlockDriverState *bs);
 
 bool coroutine_fn bdrv_co_can_store_new_dirty_bitmap(BlockDriverState *bs,

include/block/block_int-common.h

@@ -725,7 +725,7 @@ struct BlockDriver {
     void (*bdrv_debug_event)(BlockDriverState *bs, BlkdebugEvent event);
 
     /* io queue for linux-aio */
-    void (*bdrv_io_plug)(BlockDriverState *bs);
+    void coroutine_fn (*bdrv_co_io_plug)(BlockDriverState *bs);
     void (*bdrv_io_unplug)(BlockDriverState *bs);
 
     /**

include/sysemu/block-backend-io.h

@@ -74,7 +74,9 @@ void blk_iostatus_set_err(BlockBackend *blk, int error);
 int blk_get_max_iov(BlockBackend *blk);
 int blk_get_max_hw_iov(BlockBackend *blk);
 
-void blk_io_plug(BlockBackend *blk);
+void coroutine_fn blk_co_io_plug(BlockBackend *blk);
+void co_wrapper blk_io_plug(BlockBackend *blk);
+
 void blk_io_unplug(BlockBackend *blk);
 AioContext *blk_get_aio_context(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);