Merge remote-tracking branch 'remotes/cody/tags/block-pull-request' into staging

# gpg: Signature made Fri 14 Aug 2015 14:54:27 BST using RSA key ID C0DE3057
# gpg: Good signature from "Jeffrey Cody <jcody@redhat.com>"
# gpg:                 aka "Jeffrey Cody <jeff@codyprime.org>"
# gpg:                 aka "Jeffrey Cody <codyprime@gmail.com>"
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# Primary key fingerprint: 9957 4B4D 3474 90E7 9D98  D624 BDBE 7B27 C0DE 3057

* remotes/cody/tags/block-pull-request:
  mirror: Fix coroutine reentrance
  block/mirror: limit qiov to IOV_MAX elements

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 15 insertions, 5 deletions

diff --git a/block/mirror.c b/block/mirror.c
index fc4d8f561e..94744432eb 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -60,6 +60,7 @@ typedef struct MirrorBlockJob {
     int sectors_in_flight;
     int ret;
     bool unmap;
+    bool waiting_for_io;
 } MirrorBlockJob;
 
 typedef struct MirrorOp {
@@ -114,11 +115,7 @@ static void mirror_iteration_done(MirrorOp *op, int ret)
     qemu_iovec_destroy(&op->qiov);
     g_slice_free(MirrorOp, op);
 
-    /* Enter coroutine when it is not sleeping.  The coroutine sleeps to
-     * rate-limit itself.  The coroutine will eventually resume since there is
-     * a sleep timeout so don't wake it early.
-     */
-    if (s->common.busy) {
+    if (s->waiting_for_io) {
         qemu_coroutine_enter(s->common.co, NULL);
     }
 }
@@ -203,7 +200,9 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
     /* Wait for I/O to this cluster (from a previous iteration) to be done.  */
     while (test_bit(next_chunk, s->in_flight_bitmap)) {
         trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
+        s->waiting_for_io = true;
         qemu_coroutine_yield();
+        s->waiting_for_io = false;
     }
 
     do {
@@ -239,12 +238,18 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
          */
         while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
             trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
+            s->waiting_for_io = true;
             qemu_coroutine_yield();
+            s->waiting_for_io = false;
         }
         if (s->buf_free_count < nb_chunks + added_chunks) {
             trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
             break;
         }
+        if (IOV_MAX < nb_chunks + added_chunks) {
+            trace_mirror_break_iov_max(s, nb_chunks, added_chunks);
+            break;
+        }
 
         /* We have enough free space to copy these sectors.  */
         bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
@@ -333,7 +338,9 @@ static void mirror_free_init(MirrorBlockJob *s)
 static void mirror_drain(MirrorBlockJob *s)
 {
     while (s->in_flight > 0) {
+        s->waiting_for_io = true;
         qemu_coroutine_yield();
+        s->waiting_for_io = false;
     }
 }
 
@@ -506,7 +513,9 @@ static void coroutine_fn mirror_run(void *opaque)
             if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
                 (cnt == 0 && s->in_flight > 0)) {
                 trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
+                s->waiting_for_io = true;
                 qemu_coroutine_yield();
+                s->waiting_for_io = false;
                 continue;
             } else if (cnt != 0) {
                 delay_ns = mirror_iteration(s);
diff --git a/trace-events b/trace-events
index 94bf3bb184..8f9614adb5 100644
--- a/trace-events
+++ b/trace-events
@@ -94,6 +94,7 @@ mirror_yield(void *s, int64_t cnt, int buf_free_count, int in_flight) "s %p dirt
 mirror_yield_in_flight(void *s, int64_t sector_num, int in_flight) "s %p sector_num %"PRId64" in_flight %d"
 mirror_yield_buf_busy(void *s, int nb_chunks, int in_flight) "s %p requested chunks %d in_flight %d"
 mirror_break_buf_busy(void *s, int nb_chunks, int in_flight) "s %p requested chunks %d in_flight %d"
+mirror_break_iov_max(void *s, int nb_chunks, int added_chunks) "s %p requested chunks %d added_chunks %d"
 
 # block/backup.c
 backup_do_cow_enter(void *job, int64_t start, int64_t sector_num, int nb_sectors) "job %p start %"PRId64" sector_num %"PRId64" nb_sectors %d"