[Qemu-block] [PATCH 10/17] mirror: Create mirror_co_alloc_qiov()

[Max Reitz]

By pulling this function out of mirror_co_read(), the latter becomes
simpler.  This is important so the following patches can make it more
complicated again.

Signed-off-by: Max Reitz <address@hidden>
---
 block/mirror.c | 44 ++++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 6330269156..2a131d8b99 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -293,6 +293,29 @@ static inline void coroutine_fn
     mirror_co_wait_for_any_operation(s, false);
 }
 
+/* Allocate a QEMUIOVector from the mirror buffer pool (s->buf_free) */
+static void coroutine_fn mirror_co_alloc_qiov(MirrorBlockJob *s,
+                                              QEMUIOVector *qiov,
+                                              int64_t offset, uint64_t bytes)
+{
+    int nb_chunks = DIV_ROUND_UP(bytes, s->granularity);
+
+    while (s->buf_free_count < nb_chunks) {
+        trace_mirror_yield_in_flight(s, offset, s->in_flight);
+        mirror_co_wait_for_free_in_flight_slot(s);
+    }
+
+    qemu_iovec_init(qiov, nb_chunks);
+    while (nb_chunks-- > 0) {
+        MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
+        size_t remaining = bytes - qiov->size;
+
+        QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
+        s->buf_free_count--;
+        qemu_iovec_add(qiov, buf, MIN(s->granularity, remaining));
+    }
+}
+
 /*
  * Restrict *bytes to how much we can actually handle, and align the
  * [*offset, *bytes] range to clusters if COW is needed.
@@ -327,28 +350,9 @@ static void coroutine_fn mirror_co_read(void *opaque)
 {
     MirrorOp *op = opaque;
     MirrorBlockJob *s = op->s;
-    int nb_chunks;
     uint64_t ret;
 
-    nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
-
-    while (s->buf_free_count < nb_chunks) {
-        trace_mirror_yield_in_flight(s, op->offset, s->in_flight);
-        mirror_co_wait_for_free_in_flight_slot(s);
-    }
-
-    /* Now make a QEMUIOVector taking enough granularity-sized chunks
-     * from s->buf_free.
-     */
-    qemu_iovec_init(&op->qiov, nb_chunks);
-    while (nb_chunks-- > 0) {
-        MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
-        size_t remaining = op->bytes - op->qiov.size;
-
-        QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
-        s->buf_free_count--;
-        qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
-    }
+    mirror_co_alloc_qiov(s, &op->qiov, op->offset, op->bytes);
 
     /* Copy the dirty cluster.  */
     s->in_flight++;
-- 
2.17.1