block/coroutines: I/O and "I/O or GS" API

block coroutines functions run in different aiocontext, and are
not protected by the BQL. Therefore are I/O.

On the other side, generated_co_wrapper functions use BDRV_POLL_WHILE,
meaning the caller can either be the main loop or a specific iothread.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-25-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -5454,6 +5454,7 @@ fail:
 int coroutine_fn bdrv_co_check(BlockDriverState *bs,
                                BdrvCheckResult *res, BdrvCheckMode fix)
 {
+    IO_CODE();
     if (bs->drv == NULL) {
         return -ENOMEDIUM;
     }
@@ -6663,6 +6664,7 @@ int bdrv_activate(BlockDriverState *bs, Error **errp)
 int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp)
 {
     Error *local_err = NULL;
+    IO_CODE();
 
     assert(!(bs->open_flags & BDRV_O_INACTIVE));
 

block/block-backend.c

@@ -1290,6 +1290,7 @@ blk_co_do_preadv(BlockBackend *blk, int64_t offset, int64_t bytes,
 {
     int ret;
     BlockDriverState *bs;
+    IO_CODE();
 
     blk_wait_while_drained(blk);
 
@@ -1337,6 +1338,7 @@ blk_co_do_pwritev_part(BlockBackend *blk, int64_t offset, int64_t bytes,
 {
     int ret;
     BlockDriverState *bs;
+    IO_CODE();
 
     blk_wait_while_drained(blk);
 
@@ -1656,6 +1658,8 @@ void blk_aio_cancel_async(BlockAIOCB *acb)
 int coroutine_fn
 blk_co_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
 {
+    IO_CODE();
+
     blk_wait_while_drained(blk);
 
     if (!blk_is_available(blk)) {
@@ -1699,6 +1703,7 @@ int coroutine_fn
 blk_co_do_pdiscard(BlockBackend *blk, int64_t offset, int64_t bytes)
 {
     int ret;
+    IO_CODE();
 
     blk_wait_while_drained(blk);
 
@@ -1757,6 +1762,7 @@ int blk_pdiscard(BlockBackend *blk, int64_t offset, int64_t bytes)
 int coroutine_fn blk_co_do_flush(BlockBackend *blk)
 {
     blk_wait_while_drained(blk);
+    IO_CODE();
 
     if (!blk_is_available(blk)) {
         return -ENOMEDIUM;

block/coroutines.h

@@ -30,17 +30,17 @@
 /* For blk_bs() in generated block/block-gen.c */
 #include "sysemu/block-backend.h"
 
+/*
+ * I/O API functions. These functions are thread-safe.
+ *
+ * See include/block/block-io.h for more information about
+ * the I/O API.
+ */
+
 int coroutine_fn bdrv_co_check(BlockDriverState *bs,
                                BdrvCheckResult *res, BdrvCheckMode fix);
 int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp);
 
-int generated_co_wrapper
-bdrv_preadv(BdrvChild *child, int64_t offset, unsigned int bytes,
-            QEMUIOVector *qiov, BdrvRequestFlags flags);
-int generated_co_wrapper
-bdrv_pwritev(BdrvChild *child, int64_t offset, unsigned int bytes,
-             QEMUIOVector *qiov, BdrvRequestFlags flags);
-
 int coroutine_fn
 bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   BlockDriverState *base,
@@ -52,6 +52,51 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   int64_t *map,
                                   BlockDriverState **file,
                                   int *depth);
+
+int coroutine_fn bdrv_co_readv_vmstate(BlockDriverState *bs,
+                                       QEMUIOVector *qiov, int64_t pos);
+int coroutine_fn bdrv_co_writev_vmstate(BlockDriverState *bs,
+                                        QEMUIOVector *qiov, int64_t pos);
+
+int coroutine_fn
+nbd_co_do_establish_connection(BlockDriverState *bs, Error **errp);
+
+
+int coroutine_fn
+blk_co_do_preadv(BlockBackend *blk, int64_t offset, int64_t bytes,
+                 QEMUIOVector *qiov, BdrvRequestFlags flags);
+
+
+int coroutine_fn
+blk_co_do_pwritev_part(BlockBackend *blk, int64_t offset, int64_t bytes,
+                       QEMUIOVector *qiov, size_t qiov_offset,
+                       BdrvRequestFlags flags);
+
+int coroutine_fn
+blk_co_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
+
+int coroutine_fn
+blk_co_do_pdiscard(BlockBackend *blk, int64_t offset, int64_t bytes);
+
+int coroutine_fn blk_co_do_flush(BlockBackend *blk);
+
+
+/*
+ * "I/O or GS" API functions. These functions can run without
+ * the BQL, but only in one specific iothread/main loop.
+ *
+ * See include/block/block-io.h for more information about
+ * the "I/O or GS" API.
+ */
+
+int generated_co_wrapper
+bdrv_preadv(BdrvChild *child, int64_t offset, unsigned int bytes,
+            QEMUIOVector *qiov, BdrvRequestFlags flags);
+
+int generated_co_wrapper
+bdrv_pwritev(BdrvChild *child, int64_t offset, unsigned int bytes,
+             QEMUIOVector *qiov, BdrvRequestFlags flags);
+
 int generated_co_wrapper
 bdrv_common_block_status_above(BlockDriverState *bs,
                                BlockDriverState *base,
@@ -63,46 +108,24 @@ bdrv_common_block_status_above(BlockDriverState *bs,
                                int64_t *map,
                                BlockDriverState **file,
                                int *depth);
-
-int coroutine_fn bdrv_co_readv_vmstate(BlockDriverState *bs,
-                                       QEMUIOVector *qiov, int64_t pos);
-int coroutine_fn bdrv_co_writev_vmstate(BlockDriverState *bs,
-                                        QEMUIOVector *qiov, int64_t pos);
-
 int generated_co_wrapper
 nbd_do_establish_connection(BlockDriverState *bs, Error **errp);
-int coroutine_fn
-nbd_co_do_establish_connection(BlockDriverState *bs, Error **errp);
-
 
 int generated_co_wrapper
 blk_do_preadv(BlockBackend *blk, int64_t offset, int64_t bytes,
               QEMUIOVector *qiov, BdrvRequestFlags flags);
-int coroutine_fn
-blk_co_do_preadv(BlockBackend *blk, int64_t offset, int64_t bytes,
-                 QEMUIOVector *qiov, BdrvRequestFlags flags);
-
 
 int generated_co_wrapper
 blk_do_pwritev_part(BlockBackend *blk, int64_t offset, int64_t bytes,
                     QEMUIOVector *qiov, size_t qiov_offset,
                     BdrvRequestFlags flags);
-int coroutine_fn
-blk_co_do_pwritev_part(BlockBackend *blk, int64_t offset, int64_t bytes,
-                       QEMUIOVector *qiov, size_t qiov_offset,
-                       BdrvRequestFlags flags);
 
 int generated_co_wrapper
 blk_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
-int coroutine_fn
-blk_co_do_ioctl(BlockBackend *blk, unsigned long int req, void *buf);
 
 int generated_co_wrapper
 blk_do_pdiscard(BlockBackend *blk, int64_t offset, int64_t bytes);
-int coroutine_fn
-blk_co_do_pdiscard(BlockBackend *blk, int64_t offset, int64_t bytes);
 
 int generated_co_wrapper blk_do_flush(BlockBackend *blk);
-int coroutine_fn blk_co_do_flush(BlockBackend *blk);
 
 #endif /* BLOCK_COROUTINES_INT_H */

block/io.c

@@ -2678,6 +2678,7 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
     BlockDriverState *p;
     int64_t eof = 0;
     int dummy;
+    IO_CODE();
 
     assert(!include_base || base); /* Can't include NULL base */
 
@@ -2867,6 +2868,7 @@ bdrv_co_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
     BlockDriver *drv = bs->drv;
     BlockDriverState *child_bs = bdrv_primary_bs(bs);
     int ret;
+    IO_CODE();
 
     ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
     if (ret < 0) {
@@ -2898,6 +2900,7 @@ bdrv_co_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
     BlockDriver *drv = bs->drv;
     BlockDriverState *child_bs = bdrv_primary_bs(bs);
     int ret;
+    IO_CODE();
 
     ret = bdrv_check_qiov_request(pos, qiov->size, qiov, 0, NULL);
     if (ret < 0) {

block/nbd.c

@@ -313,6 +313,7 @@ int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs,
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     int ret;
     bool blocking = nbd_client_connecting_wait(s);
+    IO_CODE();
 
     assert(!s->ioc);