[PATCH v2 4/7] block-copy: add a CoMutex to the BlockCopyTask list

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

Because the list of tasks is only modified by coroutine
functions, add a CoMutex in order to protect them.

Use the same mutex to protect also BlockCopyState in_flight_bytes
field to avoid adding additional syncronization primitives.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/block-copy.c | 55 +++++++++++++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 20 deletions(-)

diff --git a/block/block-copy.c b/block/block-copy.c
index 2e610b4142..3a949fab64 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -83,7 +83,7 @@ typedef struct BlockCopyTask {
      */
     bool zeroes;
 
-    /* State */
+    /* State. Protected by tasks_lock */
     CoQueue wait_queue; /* coroutines blocked on this task */
 
     /* To reference all call states from BlockCopyState */
@@ -106,8 +106,9 @@ typedef struct BlockCopyState {
     BdrvChild *target;
 
     /* State */
-    int64_t in_flight_bytes;
+    int64_t in_flight_bytes; /* protected by tasks_lock */
     BlockCopyMethod method;
+    CoMutex tasks_lock;
     QLIST_HEAD(, BlockCopyTask) tasks; /* All tasks from all block-copy calls */
     QLIST_HEAD(, BlockCopyCallState) calls;
     /* State fields that use a thread-safe API */
@@ -142,8 +143,10 @@ typedef struct BlockCopyState {
     bool skip_unallocated;
 } BlockCopyState;
 
-static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
-                                            int64_t offset, int64_t bytes)
+/* Called with lock held */
+static BlockCopyTask *find_conflicting_task_locked(BlockCopyState *s,
+                                                   int64_t offset,
+                                                   int64_t bytes)
 {
     BlockCopyTask *t;
 
@@ -163,13 +166,16 @@ static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
 static bool coroutine_fn block_copy_wait_one(BlockCopyState *s, int64_t offset,
                                              int64_t bytes)
 {
-    BlockCopyTask *task = find_conflicting_task(s, offset, bytes);
+    BlockCopyTask *task;
+
+    QEMU_LOCK_GUARD(&s->tasks_lock);
+    task = find_conflicting_task_locked(s, offset, bytes);
 
     if (!task) {
         return false;
     }
 
-    qemu_co_queue_wait(&task->wait_queue, NULL);
+    qemu_co_queue_wait(&task->wait_queue, &s->tasks_lock);
 
     return true;
 }
@@ -213,11 +219,7 @@ static coroutine_fn BlockCopyTask *block_copy_task_create(BlockCopyState *s,
     assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
     bytes = QEMU_ALIGN_UP(bytes, s->cluster_size);
 
-    /* region is dirty, so no existent tasks possible in it */
-    assert(!find_conflicting_task(s, offset, bytes));
-
     bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
-    s->in_flight_bytes += bytes;
 
     task = g_new(BlockCopyTask, 1);
     *task = (BlockCopyTask) {
@@ -228,7 +230,13 @@ static coroutine_fn BlockCopyTask *block_copy_task_create(BlockCopyState *s,
         .bytes = bytes,
     };
     qemu_co_queue_init(&task->wait_queue);
-    QLIST_INSERT_HEAD(&s->tasks, task, list);
+
+    WITH_QEMU_LOCK_GUARD(&s->tasks_lock) {
+        s->in_flight_bytes += bytes;
+        /* region is dirty, so no existent tasks possible in it */
+        assert(!find_conflicting_task_locked(s, offset, bytes));
+        QLIST_INSERT_HEAD(&s->tasks, task, list);
+    }
 
     return task;
 }
@@ -249,25 +257,29 @@ static void coroutine_fn block_copy_task_shrink(BlockCopyTask *task,
 
     assert(new_bytes > 0 && new_bytes < task->bytes);
 
-    task->s->in_flight_bytes -= task->bytes - new_bytes;
     bdrv_set_dirty_bitmap(task->s->copy_bitmap,
                           task->offset + new_bytes, task->bytes - new_bytes);
 
-    task->bytes = new_bytes;
-    qemu_co_queue_restart_all(&task->wait_queue);
+    WITH_QEMU_LOCK_GUARD(&task->s->tasks_lock) {
+        task->s->in_flight_bytes -= task->bytes - new_bytes;
+        task->bytes = new_bytes;
+        qemu_co_queue_restart_all(&task->wait_queue);
+    }
 }
 
 static void coroutine_fn block_copy_task_end(BlockCopyTask *task, int ret)
 {
-    task->s->in_flight_bytes -= task->bytes;
     if (ret < 0) {
         bdrv_set_dirty_bitmap(task->s->copy_bitmap, task->offset, task->bytes);
     }
-    QLIST_REMOVE(task, list);
-    progress_set_remaining(task->s->progress,
-                           bdrv_get_dirty_count(task->s->copy_bitmap) +
-                           task->s->in_flight_bytes);
-    qemu_co_queue_restart_all(&task->wait_queue);
+    WITH_QEMU_LOCK_GUARD(&task->s->tasks_lock) {
+        task->s->in_flight_bytes -= task->bytes;
+        QLIST_REMOVE(task, list);
+        progress_set_remaining(task->s->progress,
+                               bdrv_get_dirty_count(task->s->copy_bitmap) +
+                               task->s->in_flight_bytes);
+        qemu_co_queue_restart_all(&task->wait_queue);
+    }
 }
 
 void block_copy_state_free(BlockCopyState *s)
@@ -336,6 +348,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
     }
 
     ratelimit_init(&s->rate_limit);
+    qemu_co_mutex_init(&s->tasks_lock);
     QLIST_INIT(&s->tasks);
     QLIST_INIT(&s->calls);
 
@@ -586,9 +599,11 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
 
     if (!ret) {
         bdrv_reset_dirty_bitmap(s->copy_bitmap, offset, bytes);
+        qemu_co_mutex_lock(&s->tasks_lock);
         progress_set_remaining(s->progress,
                                bdrv_get_dirty_count(s->copy_bitmap) +
                                s->in_flight_bytes);
+        qemu_co_mutex_unlock(&s->tasks_lock);
     }
 
     *count = bytes;
-- 
2.30.2