[Qemu-devel] [PATCH 07/18] block: introduce bdrv_poll_while and bdrv_wakeup

[Paolo Bonzini <pbonzini@redhat.com>]

We want the BDS event loop to run exclusively in the iothread that
owns the BDS's AioContext.  This function and macro provides the
synchronization between the two event loops.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/block-backend.c     |  7 +------
 block/io.c                | 47 +++++++++++------------------------------------
 block/qed-table.c         | 16 ++++------------
 block/qed.c               |  4 +++-
 include/block/block.h     |  9 +++++++++
 include/block/block_int.h |  1 +
 6 files changed, 29 insertions(+), 55 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 234df1e..c5c2597 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -878,7 +878,6 @@ static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
                    int64_t bytes, CoroutineEntry co_entry,
                    BdrvRequestFlags flags)
 {
-    AioContext *aio_context;
     QEMUIOVector qiov;
     struct iovec iov;
     Coroutine *co;
@@ -900,11 +899,7 @@ static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
 
     co = qemu_coroutine_create(co_entry, &rwco);
     qemu_coroutine_enter(co);
-
-    aio_context = blk_get_aio_context(blk);
-    while (rwco.ret == NOT_DONE) {
-        aio_poll(aio_context, true);
-    }
+    bdrv_poll_while(blk_bs(blk), rwco.ret == NOT_DONE);
 
     return rwco.ret;
 }
diff --git a/block/io.c b/block/io.c
index afec968..7d3dcfc 100644
--- a/block/io.c
+++ b/block/io.c
@@ -156,23 +156,12 @@ bool bdrv_requests_pending(BlockDriverState *bs)
     return false;
 }
 
-static bool bdrv_drain_poll(BlockDriverState *bs)
-{
-    bool waited = false;
-
-    while (atomic_read(&bs->in_flight) > 0) {
-        aio_poll(bdrv_get_aio_context(bs), true);
-        waited = true;
-    }
-    return waited;
-}
-
 static bool bdrv_drain_recurse(BlockDriverState *bs)
 {
     BdrvChild *child;
     bool waited;
 
-    waited = bdrv_drain_poll(bs);
+    waited = bdrv_poll_while(bs, atomic_read(&bs->in_flight) > 0);
 
     if (bs->drv && bs->drv->bdrv_drain) {
         bs->drv->bdrv_drain(bs);
@@ -485,9 +474,14 @@ void bdrv_inc_in_flight(BlockDriverState *bs)
     atomic_inc(&bs->in_flight);
 }
 
+void bdrv_wakeup(BlockDriverState *bs)
+{
+}
+
 void bdrv_dec_in_flight(BlockDriverState *bs)
 {
     atomic_dec(&bs->in_flight);
+    bdrv_wakeup(bs);
 }
 
 static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
@@ -597,13 +591,9 @@ static int bdrv_prwv_co(BdrvChild *child, int64_t offset,
         /* Fast-path if already in coroutine context */
         bdrv_rw_co_entry(&rwco);
     } else {
-        AioContext *aio_context = bdrv_get_aio_context(child->bs);
-
         co = qemu_coroutine_create(bdrv_rw_co_entry, &rwco);
         qemu_coroutine_enter(co);
-        while (rwco.ret == NOT_DONE) {
-            aio_poll(aio_context, true);
-        }
+        bdrv_poll_while(child->bs, rwco.ret == NOT_DONE);
     }
     return rwco.ret;
 }
@@ -1845,14 +1835,10 @@ int64_t bdrv_get_block_status_above(BlockDriverState *bs,
         /* Fast-path if already in coroutine context */
         bdrv_get_block_status_above_co_entry(&data);
     } else {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
         co = qemu_coroutine_create(bdrv_get_block_status_above_co_entry,
                                    &data);
         qemu_coroutine_enter(co);
-        while (!data.done) {
-            aio_poll(aio_context, true);
-        }
+        bdrv_poll_while(bs, !data.done);
     }
     return data.ret;
 }
@@ -2411,13 +2397,9 @@ int bdrv_flush(BlockDriverState *bs)
         /* Fast-path if already in coroutine context */
         bdrv_flush_co_entry(&flush_co);
     } else {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
         co = qemu_coroutine_create(bdrv_flush_co_entry, &flush_co);
         qemu_coroutine_enter(co);
-        while (flush_co.ret == NOT_DONE) {
-            aio_poll(aio_context, true);
-        }
+        bdrv_poll_while(bs, flush_co.ret == NOT_DONE);
     }
 
     return flush_co.ret;
@@ -2543,13 +2525,9 @@ int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count)
         /* Fast-path if already in coroutine context */
         bdrv_pdiscard_co_entry(&rwco);
     } else {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
         co = qemu_coroutine_create(bdrv_pdiscard_co_entry, &rwco);
         qemu_coroutine_enter(co);
-        while (rwco.ret == NOT_DONE) {
-            aio_poll(aio_context, true);
-        }
+        bdrv_poll_while(bs, rwco.ret == NOT_DONE);
     }
 
     return rwco.ret;
@@ -2608,11 +2586,8 @@ int bdrv_ioctl(BlockDriverState *bs, unsigned long int req, void *buf)
         bdrv_co_ioctl_entry(&data);
     } else {
         Coroutine *co = qemu_coroutine_create(bdrv_co_ioctl_entry, &data);
-
         qemu_coroutine_enter(co);
-        while (data.ret == -EINPROGRESS) {
-            aio_poll(bdrv_get_aio_context(bs), true);
-        }
+        bdrv_poll_while(bs, data.ret == -EINPROGRESS);
     }
     return data.ret;
 }
diff --git a/block/qed-table.c b/block/qed-table.c
index 1a731df..b7d53ce 100644
--- a/block/qed-table.c
+++ b/block/qed-table.c
@@ -174,9 +174,7 @@ int qed_read_l1_table_sync(BDRVQEDState *s)
 
     qed_read_table(s, s->header.l1_table_offset,
                    s->l1_table, qed_sync_cb, &ret);
-    while (ret == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(s->bs), true);
-    }
+    bdrv_poll_while(s->bs, ret == -EINPROGRESS);
 
     return ret;
 }
@@ -195,9 +193,7 @@ int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
     int ret = -EINPROGRESS;
 
     qed_write_l1_table(s, index, n, qed_sync_cb, &ret);
-    while (ret == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(s->bs), true);
-    }
+    bdrv_poll_while(s->bs, ret == -EINPROGRESS);
 
     return ret;
 }
@@ -268,9 +264,7 @@ int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request, uint64_t offset
     int ret = -EINPROGRESS;
 
     qed_read_l2_table(s, request, offset, qed_sync_cb, &ret);
-    while (ret == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(s->bs), true);
-    }
+    bdrv_poll_while(s->bs, ret == -EINPROGRESS);
 
     return ret;
 }
@@ -290,9 +284,7 @@ int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
     int ret = -EINPROGRESS;
 
     qed_write_l2_table(s, request, index, n, flush, qed_sync_cb, &ret);
-    while (ret == -EINPROGRESS) {
-        aio_poll(bdrv_get_aio_context(s->bs), true);
-    }
+    bdrv_poll_while(s->bs, ret == -EINPROGRESS);
 
     return ret;
 }
diff --git a/block/qed.c b/block/qed.c
index 1a7ef0a..dcb5fb9 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -354,7 +354,9 @@ static void qed_start_need_check_timer(BDRVQEDState *s)
 static void qed_cancel_need_check_timer(BDRVQEDState *s)
 {
     trace_qed_cancel_need_check_timer(s);
-    timer_del(s->need_check_timer);
+    if (s->need_check_timer) {
+        timer_del(s->need_check_timer);
+    }
 }
 
 static void bdrv_qed_detach_aio_context(BlockDriverState *bs)
diff --git a/include/block/block.h b/include/block/block.h
index 107c603..876a1e7 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -340,6 +340,15 @@ void bdrv_drain(BlockDriverState *bs);
 void coroutine_fn bdrv_co_drain(BlockDriverState *bs);
 void bdrv_drain_all(void);
 
+#define bdrv_poll_while(bs, cond) ({                       \
+    bool waited_ = false;                                  \
+    BlockDriverState *bs_ = (bs);                          \
+    while ((cond)) {                                       \
+        aio_poll(bdrv_get_aio_context(bs_), true);         \
+        waited_ = true;                                    \
+    }                                                      \
+    waited_; })
+
 int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count);
 int bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset, int count);
 int bdrv_has_zero_init_1(BlockDriverState *bs);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 5a7308b..11f877b 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -786,6 +786,7 @@ void bdrv_undo_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *in);
 
 void bdrv_inc_in_flight(BlockDriverState *bs);
 void bdrv_dec_in_flight(BlockDriverState *bs);
+void bdrv_wakeup(BlockDriverState *bs);
 
 void blockdev_close_all_bdrv_states(void);
 
-- 
2.7.4