Re: [Qemu-block] [PATCH 02/19] block: Use bdrv_do_drain_begin/end in bdrv_drain_all()

[Stefan Hajnoczi]

On Wed, Apr 11, 2018 at 06:39:23PM +0200, Kevin Wolf wrote:
> bdrv_do_drain_begin/end() implement already everything that
> bdrv_drain_all_begin/end() need and currently still do manually: Disable
> external events, call parent drain callbacks, call block driver
> callbacks.
> 
> It also does two more things:
> 
> The first is incrementing bs->quiesce_counter. bdrv_drain_all() already
> stood out in the test case by behaving different from the other drain
> variants. Adding this is not only safe, but in fact a bug fix.
> 
> The second is calling bdrv_drain_recurse(). We already do that later in
> the same function in a loop, so basically doing an early first iteration
> doesn't hurt.
> 
> Signed-off-by: Kevin Wolf 
> ---
>  block/io.c  | 10 ++
>  tests/test-bdrv-drain.c | 14 --
>  2 files changed, 6 insertions(+), 18 deletions(-)

Reviewed-by: Stefan Hajnoczi 


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[Qemu-block] [PATCH 02/19] block: Use bdrv_do_drain_begin/end in bdrv_drain_all()

[Kevin Wolf]

bdrv_do_drain_begin/end() implement already everything that
bdrv_drain_all_begin/end() need and currently still do manually: Disable
external events, call parent drain callbacks, call block driver
callbacks.

It also does two more things:

The first is incrementing bs->quiesce_counter. bdrv_drain_all() already
stood out in the test case by behaving different from the other drain
variants. Adding this is not only safe, but in fact a bug fix.

The second is calling bdrv_drain_recurse(). We already do that later in
the same function in a loop, so basically doing an early first iteration
doesn't hurt.

Signed-off-by: Kevin Wolf 
---
 block/io.c  | 10 ++
 tests/test-bdrv-drain.c | 14 --
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/block/io.c b/block/io.c
index 28e71221b0..cad59db2f4 100644
--- a/block/io.c
+++ b/block/io.c
@@ -412,11 +412,8 @@ void bdrv_drain_all_begin(void)
 for (bs = bdrv_first(); bs; bs = bdrv_next()) {
 AioContext *aio_context = bdrv_get_aio_context(bs);
 
-/* Stop things in parent-to-child order */
 aio_context_acquire(aio_context);
-aio_disable_external(aio_context);
-bdrv_parent_drained_begin(bs, NULL);
-bdrv_drain_invoke(bs, true, true);
+bdrv_do_drained_begin(bs, true, NULL);
 aio_context_release(aio_context);
 
 if (!g_slist_find(aio_ctxs, aio_context)) {
@@ -457,11 +454,8 @@ void bdrv_drain_all_end(void)
 for (bs = bdrv_first(); bs; bs = bdrv_next()) {
 AioContext *aio_context = bdrv_get_aio_context(bs);
 
-/* Re-enable things in child-to-parent order */
 aio_context_acquire(aio_context);
-bdrv_drain_invoke(bs, false, true);
-bdrv_parent_drained_end(bs, NULL);
-aio_enable_external(aio_context);
+bdrv_do_drained_end(bs, true, NULL);
 aio_context_release(aio_context);
 }
 }
diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c
index 29634102d8..cd870609c5 100644
--- a/tests/test-bdrv-drain.c
+++ b/tests/test-bdrv-drain.c
@@ -276,8 +276,7 @@ static void test_quiesce_common(enum drain_type drain_type, 
bool recursive)
 
 static void test_quiesce_drain_all(void)
 {
-// XXX drain_all doesn't quiesce
-//test_quiesce_common(BDRV_DRAIN_ALL, true);
+test_quiesce_common(BDRV_DRAIN_ALL, true);
 }
 
 static void test_quiesce_drain(void)
@@ -319,12 +318,7 @@ static void test_nested(void)
 
 for (outer = 0; outer < DRAIN_TYPE_MAX; outer++) {
 for (inner = 0; inner < DRAIN_TYPE_MAX; inner++) {
-/* XXX bdrv_drain_all() doesn't increase the quiesce_counter */
-int bs_quiesce  = (outer != BDRV_DRAIN_ALL) +
-  (inner != BDRV_DRAIN_ALL);
-int backing_quiesce = (outer == BDRV_SUBTREE_DRAIN) +
-  (inner == BDRV_SUBTREE_DRAIN);
-int backing_cb_cnt  = (outer != BDRV_DRAIN) +
+int backing_quiesce = (outer != BDRV_DRAIN) +
   (inner != BDRV_DRAIN);
 
 g_assert_cmpint(bs->quiesce_counter, ==, 0);
@@ -335,10 +329,10 @@ static void test_nested(void)
 do_drain_begin(outer, bs);
 do_drain_begin(inner, bs);
 
-g_assert_cmpint(bs->quiesce_counter, ==, bs_quiesce);
+g_assert_cmpint(bs->quiesce_counter, ==, 2);
 g_assert_cmpint(backing->quiesce_counter, ==, backing_quiesce);
 g_assert_cmpint(s->drain_count, ==, 2);
-g_assert_cmpint(backing_s->drain_count, ==, backing_cb_cnt);
+g_assert_cmpint(backing_s->drain_count, ==, backing_quiesce);
 
 do_drain_end(inner, bs);
 do_drain_end(outer, bs);
-- 
2.13.6