[Qemu-devel] [PATCH 12/12] block: Don't check throttled reqs in bdrv_requests_pending()

[Kevin Wolf <kwolf@redhat.com>]

Checking whether there are throttled requests requires going to the
associated BlockBackend, which we want to avoid. All users of
bdrv_requests_pending() already call bdrv_flush_io_queue() first, which
restarts throttled requests. We just have to use the return value of
that callback (which tells us whether any requests have been restarted)
instead of ignoring it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/io.c            | 22 ++++++++++------------
 include/block/block.h |  2 +-
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/block/io.c b/block/io.c
index f6edab8..24bdd6c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -153,17 +153,10 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs)
 bool bdrv_requests_pending(BlockDriverState *bs)
 {
     BdrvChild *child;
-    BlockBackendPublic *blkp = bs->blk ? blk_get_public(bs->blk) : NULL;
 
     if (!QLIST_EMPTY(&bs->tracked_requests)) {
         return true;
     }
-    if (blkp && !qemu_co_queue_empty(&blkp->throttled_reqs[0])) {
-        return true;
-    }
-    if (blkp && !qemu_co_queue_empty(&blkp->throttled_reqs[1])) {
-        return true;
-    }
 
     QLIST_FOREACH(child, &bs->children, next) {
         if (bdrv_requests_pending(child->bs)) {
@@ -204,8 +197,8 @@ void bdrv_drain(BlockDriverState *bs)
     bdrv_drain_recurse(bs);
     while (busy) {
         /* Keep iterating */
-         bdrv_flush_io_queue(bs);
-         busy = bdrv_requests_pending(bs);
+         busy = bdrv_flush_io_queue(bs);
+         busy |= bdrv_requests_pending(bs);
          busy |= aio_poll(bdrv_get_aio_context(bs), busy);
     }
 }
@@ -254,7 +247,9 @@ void bdrv_drain_all(void)
             aio_context_acquire(aio_context);
             while ((bs = bdrv_next(bs))) {
                 if (aio_context == bdrv_get_aio_context(bs)) {
-                    bdrv_flush_io_queue(bs);
+                    if (bdrv_flush_io_queue(bs)) {
+                        busy = true;
+                    }
                     if (bdrv_requests_pending(bs)) {
                         busy = true;
                         aio_poll(aio_context, busy);
@@ -2639,10 +2634,11 @@ void bdrv_io_unplug(BlockDriverState *bs)
     }
 }
 
-void bdrv_flush_io_queue(BlockDriverState *bs)
+bool bdrv_flush_io_queue(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
     BdrvChild *c;
+    bool new_request = false;
 
     if (drv && drv->bdrv_flush_io_queue) {
         drv->bdrv_flush_io_queue(bs);
@@ -2652,9 +2648,11 @@ void bdrv_flush_io_queue(BlockDriverState *bs)
 
     QLIST_FOREACH(c, &bs->parents, next_parent) {
         if (c->role->drain_queue) {
-            c->role->drain_queue(c);
+            new_request |= c->role->drain_queue(c);
         }
     }
+
+    return new_request;
 }
 
 void bdrv_drained_begin(BlockDriverState *bs)
diff --git a/include/block/block.h b/include/block/block.h
index 80ece12..46cee8e 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -513,7 +513,7 @@ int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
 
 void bdrv_io_plug(BlockDriverState *bs);
 void bdrv_io_unplug(BlockDriverState *bs);
-void bdrv_flush_io_queue(BlockDriverState *bs);
+bool bdrv_flush_io_queue(BlockDriverState *bs);
 
 /**
  * bdrv_drained_begin:
-- 
1.8.3.1