[Qemu-devel] [RFC][PATCH 3/9] block: Add bdrv_co_readv/writev emulation

[Kevin Wolf <kwolf@redhat.com>]

In order to be able to call bdrv_co_readv/writev for drivers that don't
implement the functions natively, add an emulation that uses the AIO functions
to implement them.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c      |   86 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 trace-events |    1 +
 2 files changed, 78 insertions(+), 9 deletions(-)

diff --git a/block.c b/block.c
index 79a5008..fc1712f 100644
--- a/block.c
+++ b/block.c
@@ -64,6 +64,12 @@ static BlockDriverAIOCB *bdrv_co_aio_readv_em(BlockDriverState *bs,
 static BlockDriverAIOCB *bdrv_co_aio_writev_em(BlockDriverState *bs,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque);
+static int coroutine_fn bdrv_co_readv_em(BlockDriverState *bs,
+                                         int64_t sector_num, int nb_sectors,
+                                         QEMUIOVector *iov);
+static int coroutine_fn bdrv_co_writev_em(BlockDriverState *bs,
+                                         int64_t sector_num, int nb_sectors,
+                                         QEMUIOVector *iov);
 
 static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
     QTAILQ_HEAD_INITIALIZER(bdrv_states);
@@ -182,14 +188,19 @@ void bdrv_register(BlockDriver *bdrv)
         bdrv->bdrv_aio_writev = bdrv_co_aio_writev_em;
         bdrv->bdrv_read = bdrv_read_em;
         bdrv->bdrv_write = bdrv_write_em;
-     } else if (!bdrv->bdrv_aio_readv) {
-        /* add AIO emulation layer */
-        bdrv->bdrv_aio_readv = bdrv_aio_readv_em;
-        bdrv->bdrv_aio_writev = bdrv_aio_writev_em;
-    } else if (!bdrv->bdrv_read) {
-        /* add synchronous IO emulation layer */
-        bdrv->bdrv_read = bdrv_read_em;
-        bdrv->bdrv_write = bdrv_write_em;
+     } else {
+        bdrv->bdrv_co_readv = bdrv_co_readv_em;
+        bdrv->bdrv_co_writev = bdrv_co_writev_em;
+
+        if (!bdrv->bdrv_aio_readv) {
+            /* add AIO emulation layer */
+            bdrv->bdrv_aio_readv = bdrv_aio_readv_em;
+            bdrv->bdrv_aio_writev = bdrv_aio_writev_em;
+        } else if (!bdrv->bdrv_read) {
+            /* add synchronous IO emulation layer */
+            bdrv->bdrv_read = bdrv_read_em;
+            bdrv->bdrv_write = bdrv_write_em;
+        }
     }
 
     if (!bdrv->bdrv_aio_flush)
@@ -2652,7 +2663,7 @@ static void coroutine_fn bdrv_co_rw(void *opaque)
     BlockDriverAIOCBCoroutine *acb = opaque;
     BlockDriverState *bs = acb->common.bs;
 
-    if (acb->is_write) {
+    if (!acb->is_write) {
         acb->req.error = bs->drv->bdrv_co_readv(bs, acb->req.sector,
             acb->req.nb_sectors, acb->req.qiov);
     } else {
@@ -2849,6 +2860,63 @@ void qemu_aio_release(void *p)
 }
 
 /**************************************************************/
+/* Coroutine block device emulation */
+
+typedef struct CoroutineIOCompletion {
+    Coroutine *coroutine;
+    int ret;
+} CoroutineIOCompletion;
+
+static void bdrv_co_io_em_complete(void *opaque, int ret)
+{
+    CoroutineIOCompletion *co = opaque;
+
+    co->ret = ret;
+    qemu_coroutine_enter(co->coroutine, NULL);
+}
+
+static int coroutine_fn bdrv_co_io_em(BlockDriverState *bs, int64_t sector_num,
+                                      int nb_sectors, QEMUIOVector *iov,
+                                      bool is_write)
+{
+    CoroutineIOCompletion co = {
+        .coroutine = qemu_coroutine_self(),
+        .ret = -EINPROGRESS,
+    };
+    BlockDriverAIOCB *acb;
+
+    if (is_write) {
+        acb = bdrv_aio_writev(bs, sector_num, iov, nb_sectors,
+                              bdrv_co_io_em_complete, &co);
+    } else {
+        acb = bdrv_aio_readv(bs, sector_num, iov, nb_sectors,
+                             bdrv_co_io_em_complete, &co);
+    }
+
+    trace_bdrv_co_io(is_write, acb);
+    if (!acb) {
+        return -EIO;
+    }
+    qemu_coroutine_yield();
+
+    return co.ret;
+}
+
+static int coroutine_fn bdrv_co_readv_em(BlockDriverState *bs,
+                                         int64_t sector_num, int nb_sectors,
+                                         QEMUIOVector *iov)
+{
+    return bdrv_co_io_em(bs, sector_num, nb_sectors, iov, false);
+}
+
+static int coroutine_fn bdrv_co_writev_em(BlockDriverState *bs,
+                                         int64_t sector_num, int nb_sectors,
+                                         QEMUIOVector *iov)
+{
+    return bdrv_co_io_em(bs, sector_num, nb_sectors, iov, true);
+}
+
+/**************************************************************/
 /* removable device support */
 
 /**
diff --git a/trace-events b/trace-events
index 3cd9118..b835c61 100644
--- a/trace-events
+++ b/trace-events
@@ -57,6 +57,7 @@ disable bdrv_aio_writev(void *bs, int64_t sector_num, int nb_sectors, void *opaq
 disable bdrv_set_locked(void *bs, int locked) "bs %p locked %d"
 disable bdrv_co_readv(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
 disable bdrv_co_writev(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
+disable bdrv_co_io(int is_write, void *acb) "is_write %d acb %p"
 
 # hw/virtio-blk.c
 disable virtio_blk_req_complete(void *req, int status) "req %p status %d"
-- 
1.7.6