[Qemu-devel] [RFC v2 05/15] Make qcow2_open synchronous

[Charlie Shepherd <charlie@ctshepherd.com>]

The previous patch convert all .bdrv_open functions to run from a coroutine context. However
qcow2's open method is also called from qcow2_invalidate_cache. bdrv_invalidate_cache is mainly
called by migration.c, which doesn't run in coroutine context, so rather than propagating
coroutine_fn annotations up the call chain, turn qcow2_open into a synchronous wrapper.

Signed-off-by: Charlie Shepherd <charlie@ctshepherd.com>
---
 block/qcow2.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index c6dc209..59c4200 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -58,6 +58,10 @@ typedef struct {
 #define  QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
 #define  QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
 
+
+#define NOT_DONE 0x7fffffff
+
+
 static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename)
 {
     const QCowHeader *cow_header = (const void *)buf;
@@ -315,7 +319,7 @@ static QemuOptsList qcow2_runtime_opts = {
     },
 };
 
-static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
+static int coroutine_fn qcow2_co_open(BlockDriverState *bs, QDict *options, int flags)
 {
     BDRVQcowState *s = bs->opaque;
     int len, i, ret = 0;
@@ -590,6 +594,38 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
     return ret;
 }
 
+struct QOpenCo {
+    BlockDriverState *bs;
+    QDict *options;
+    int flags;
+    int ret;
+};
+
+static void coroutine_fn qcow2_co_open_entry(void *opaque)
+{
+    struct QOpenCo *qo = opaque;
+
+    qo->ret = qcow2_co_open(qo->bs, qo->options, qo->flags);
+}
+
+static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
+{
+    Coroutine *co;
+    struct QOpenCo qo = {
+        .bs = bs,
+        .options = options,
+        .flags = flags,
+        .ret = NOT_DONE,
+    };
+
+    co = qemu_coroutine_create(qcow2_co_open_entry);
+    qemu_coroutine_enter(co, &qo);
+    while (qo.ret == NOT_DONE) {
+        qemu_aio_wait();
+    }
+    return qo.ret;
+}
+
 static int qcow2_set_key(BlockDriverState *bs, const char *key)
 {
     BDRVQcowState *s = bs->opaque;
-- 
1.8.3.2