[Qemu-block] [PATCH v3 3/8] mirror: create mirror_throttle helper

[Denis V. Lunev]

The patch also places last_pause_ns from stack in mirror_run into
MirrorBlockJob structure. This helper will be useful in next patches.

Signed-off-by: Denis V. Lunev <address@hidden>
CC: Vladimir Sementsov-Ogievskiy <address@hidden>
CC: Eric Blake <address@hidden>
CC: Stefan Hajnoczi <address@hidden>
CC: Fam Zheng <address@hidden>
CC: Kevin Wolf <address@hidden>
CC: Max Reitz <address@hidden>
CC: Jeff Cody <address@hidden>
---
 block/mirror.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 9850e54..93e2896 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -58,6 +58,7 @@ typedef struct MirrorBlockJob {
     QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
     int buf_free_count;
 
+    uint64_t last_pause_ns;
     unsigned long *in_flight_bitmap;
     int in_flight;
     int64_t sectors_in_flight;
@@ -512,6 +513,18 @@ static void mirror_exit(BlockJob *job, void *opaque)
     bdrv_unref(src);
 }
 
+static void mirror_throttle(MirrorBlockJob *s)
+{
+    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+
+    if (now - s->last_pause_ns > SLICE_TIME) {
+        s->last_pause_ns = now;
+        block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
+    } else {
+        block_job_pause_point(&s->common);
+    }
+}
+
 static void coroutine_fn mirror_run(void *opaque)
 {
     MirrorBlockJob *s = opaque;
@@ -519,7 +532,6 @@ static void coroutine_fn mirror_run(void *opaque)
     BlockDriverState *bs = blk_bs(s->common.blk);
     BlockDriverState *target_bs = blk_bs(s->target);
     int64_t sector_num, end, length;
-    uint64_t last_pause_ns;
     BlockDriverInfo bdi;
     char backing_filename[2]; /* we only need 2 characters because we are only
                                  checking for a NULL string */
@@ -575,7 +587,7 @@ static void coroutine_fn mirror_run(void *opaque)
 
     mirror_free_init(s);
 
-    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     if (!s->is_none_mode) {
         /* First part, loop on the sectors and initialize the dirty bitmap.  */
         BlockDriverState *base = s->base;
@@ -585,14 +597,8 @@ static void coroutine_fn mirror_run(void *opaque)
             /* Just to make sure we are not exceeding int limit. */
             int nb_sectors = MIN(INT_MAX >> BDRV_SECTOR_BITS,
                                  end - sector_num);
-            int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 
-            if (now - last_pause_ns > SLICE_TIME) {
-                last_pause_ns = now;
-                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
-            } else {
-                block_job_pause_point(&s->common);
-            }
+            mirror_throttle(s);
 
             if (block_job_is_cancelled(&s->common)) {
                 goto immediate_exit;
@@ -615,7 +621,7 @@ static void coroutine_fn mirror_run(void *opaque)
     bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
     for (;;) {
         uint64_t delay_ns = 0;
-        int64_t cnt;
+        int64_t cnt, delta;
         bool should_complete;
 
         if (s->ret < 0) {
@@ -638,7 +644,8 @@ static void coroutine_fn mirror_run(void *opaque)
          * We do so every SLICE_TIME nanoseconds, or when there is an error,
          * or when the source is clean, whichever comes first.
          */
-        if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < 
SLICE_TIME &&
+        delta = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - s->last_pause_ns;
+        if (delta < SLICE_TIME &&
             s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
             if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
                 (cnt == 0 && s->in_flight > 0)) {
@@ -708,7 +715,7 @@ static void coroutine_fn mirror_run(void *opaque)
             s->common.cancelled = false;
             break;
         }
-        last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+        s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     }
 
 immediate_exit:
-- 
2.5.0