[Qemu-devel] [PATCH 0/3] add bdrv_co_drain_begin/end BlockDriver callbacks

[Qemu-devel] [PATCH 0/3] add bdrv_co_drain_begin/end BlockDriver callbacks

[Manos Pitsidianakis]

This patch series renames bdrv_co_drain to bdrv_co_drain_begin and adds a new 
bdrv_co_drain_end callback to match bdrv_drained_begin/end and 
drained_begin/end of BdrvChild. This is needed because the throttle driver 
(block/throttle.c) needs a way to mark the end of the drain in order to toggle 
io_limits_disabled correctly.

Based-on: <20170918202529.28379-1-el13635@mail.ntua.gr>
    "block/throttle-groups.c: allocate RestartData on the heap"
    Which fixes a coroutine crash in block/throttle-groups.c

Manos Pitsidianakis (3):
  block: add bdrv_co_drain_end callback
  block: rename bdrv_co_drain to bdrv_co_drain_begin
  block/throttle.c: add bdrv_co_drain_begin/end callbacks

 include/block/block_int.h |  4 +++-
 block/io.c                | 42 ++++++++++++++++++++++++++++++------------
 block/qed.c               |  6 +++---
 block/throttle.c          | 18 ++++++++++++++++++
 4 files changed, 54 insertions(+), 16 deletions(-)

-- 
2.11.0

[Qemu-devel] [PATCH 1/3] block: add bdrv_co_drain_end callback

[Manos Pitsidianakis]

BlockDriverState has a bdrv_do_drain() callback but no equivalent for the end
of the drain. The throttle driver (block/throttle.c) needs a way to mark the
end of the drain in order to toggle io_limits_disabled correctly, thus
bdrv_co_drain_end is needed.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
---
 include/block/block_int.h |  2 ++
 block/io.c                | 43 +++++++++++++++++++++++++++++++------------
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index ba4c383393..ea1326e3c7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -359,6 +359,8 @@ struct BlockDriver {
      */
     void coroutine_fn (*bdrv_co_drain)(BlockDriverState *bs);
 
+    void coroutine_fn (*bdrv_co_drain_end)(BlockDriverState *bs);
+
     void (*bdrv_add_child)(BlockDriverState *parent, BlockDriverState *child,
                            Error **errp);
     void (*bdrv_del_child)(BlockDriverState *parent, BdrvChild *child,
diff --git a/block/io.c b/block/io.c
index 4378ae4c7d..465345289d 100644
--- a/block/io.c
+++ b/block/io.c
@@ -153,6 +153,7 @@ typedef struct {
     Coroutine *co;
     BlockDriverState *bs;
     bool done;
+    bool begin;
 } BdrvCoDrainData;
 
 static void coroutine_fn bdrv_drain_invoke_entry(void *opaque)
@@ -160,18 +161,23 @@ static void coroutine_fn bdrv_drain_invoke_entry(void *opaque)
     BdrvCoDrainData *data = opaque;
     BlockDriverState *bs = data->bs;
 
-    bs->drv->bdrv_co_drain(bs);
+    if (data->begin) {
+        bs->drv->bdrv_co_drain(bs);
+    } else {
+        bs->drv->bdrv_co_drain_end(bs);
+    }
 
     /* Set data->done before reading bs->wakeup.  */
     atomic_mb_set(&data->done, true);
     bdrv_wakeup(bs);
 }
 
-static void bdrv_drain_invoke(BlockDriverState *bs)
+static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)
 {
-    BdrvCoDrainData data = { .bs = bs, .done = false };
+    BdrvCoDrainData data = { .bs = bs, .done = false, .begin = begin};
 
-    if (!bs->drv || !bs->drv->bdrv_co_drain) {
+    if (!bs->drv || (begin && !bs->drv->bdrv_co_drain) ||
+            (!begin && !bs->drv->bdrv_co_drain_end)) {
         return;
     }
 
@@ -180,7 +186,7 @@ static void bdrv_drain_invoke(BlockDriverState *bs)
     BDRV_POLL_WHILE(bs, !data.done);
 }
 
-static bool bdrv_drain_recurse(BlockDriverState *bs)
+static bool bdrv_drain_recurse(BlockDriverState *bs, bool begin)
 {
     BdrvChild *child, *tmp;
     bool waited;
@@ -188,7 +194,7 @@ static bool bdrv_drain_recurse(BlockDriverState *bs)
     waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
 
     /* Ensure any pending metadata writes are submitted to bs->file.  */
-    bdrv_drain_invoke(bs);
+    bdrv_drain_invoke(bs, begin);
 
     QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
         BlockDriverState *bs = child->bs;
@@ -205,7 +211,7 @@ static bool bdrv_drain_recurse(BlockDriverState *bs)
              */
             bdrv_ref(bs);
         }
-        waited |= bdrv_drain_recurse(bs);
+        waited |= bdrv_drain_recurse(bs, begin);
         if (in_main_loop) {
             bdrv_unref(bs);
         }
@@ -221,12 +227,18 @@ static void bdrv_co_drain_bh_cb(void *opaque)
     BlockDriverState *bs = data->bs;
 
     bdrv_dec_in_flight(bs);
-    bdrv_drained_begin(bs);
+    if (data->begin) {
+        bdrv_drained_begin(bs);
+    } else {
+        bdrv_drained_end(bs);
+    }
+
     data->done = true;
     aio_co_wake(co);
 }
 
-static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
+static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs,
+                                                bool begin)
 {
     BdrvCoDrainData data;
 
@@ -239,6 +251,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
         .co = qemu_coroutine_self(),
         .bs = bs,
         .done = false,
+        .begin = begin,
     };
     bdrv_inc_in_flight(bs);
     aio_bh_schedule_oneshot(bdrv_get_aio_context(bs),
@@ -253,7 +266,7 @@ static void coroutine_fn bdrv_co_yield_to_drain(BlockDriverState *bs)
 void bdrv_drained_begin(BlockDriverState *bs)
 {
     if (qemu_in_coroutine()) {
-        bdrv_co_yield_to_drain(bs);
+        bdrv_co_yield_to_drain(bs, true);
         return;
     }
 
@@ -262,17 +275,22 @@ void bdrv_drained_begin(BlockDriverState *bs)
         bdrv_parent_drained_begin(bs);
     }
 
-    bdrv_drain_recurse(bs);
+    bdrv_drain_recurse(bs, true);
 }
 
 void bdrv_drained_end(BlockDriverState *bs)
 {
+    if (qemu_in_coroutine()) {
+        bdrv_co_yield_to_drain(bs, false);
+        return;
+    }
     assert(bs->quiesce_counter > 0);
     if (atomic_fetch_dec(&bs->quiesce_counter) > 1) {
         return;
     }
 
     bdrv_parent_drained_end(bs);
+    bdrv_drain_recurse(bs, false);
     aio_enable_external(bdrv_get_aio_context(bs));
 }
 
@@ -350,7 +368,7 @@ void bdrv_drain_all_begin(void)
             aio_context_acquire(aio_context);
             for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
                 if (aio_context == bdrv_get_aio_context(bs)) {
-                    waited |= bdrv_drain_recurse(bs);
+                    waited |= bdrv_drain_recurse(bs, true);
                 }
             }
             aio_context_release(aio_context);
@@ -371,6 +389,7 @@ void bdrv_drain_all_end(void)
         aio_context_acquire(aio_context);
         aio_enable_external(aio_context);
         bdrv_parent_drained_end(bs);
+        bdrv_drain_recurse(bs, false);
         aio_context_release(aio_context);
     }
 
-- 
2.11.0

[Qemu-devel] [PATCH 2/3] block: rename bdrv_co_drain to bdrv_co_drain_begin

[Manos Pitsidianakis]

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
---
 include/block/block_int.h | 2 +-
 block/io.c                | 4 ++--
 block/qed.c               | 6 +++---
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index ea1326e3c7..fd10f53b43 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -357,7 +357,7 @@ struct BlockDriver {
      * Drain and stop any internal sources of requests in the driver, and
      * remain so until next I/O callback (e.g. bdrv_co_writev) is called.
      */
-    void coroutine_fn (*bdrv_co_drain)(BlockDriverState *bs);
+    void coroutine_fn (*bdrv_co_drain_begin)(BlockDriverState *bs);
 
     void coroutine_fn (*bdrv_co_drain_end)(BlockDriverState *bs);
 
diff --git a/block/io.c b/block/io.c
index 465345289d..6b4b13b777 100644
--- a/block/io.c
+++ b/block/io.c
@@ -162,7 +162,7 @@ static void coroutine_fn bdrv_drain_invoke_entry(void *opaque)
     BlockDriverState *bs = data->bs;
 
     if (data->begin) {
-        bs->drv->bdrv_co_drain(bs);
+        bs->drv->bdrv_co_drain_begin(bs);
     } else {
         bs->drv->bdrv_co_drain_end(bs);
     }
@@ -176,7 +176,7 @@ static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)
 {
     BdrvCoDrainData data = { .bs = bs, .done = false, .begin = begin};
 
-    if (!bs->drv || (begin && !bs->drv->bdrv_co_drain) ||
+    if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) ||
             (!begin && !bs->drv->bdrv_co_drain_end)) {
         return;
     }
diff --git a/block/qed.c b/block/qed.c
index 28e2ec89e8..821dcaa055 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -265,7 +265,7 @@ static bool qed_plug_allocating_write_reqs(BDRVQEDState *s)
     assert(!s->allocating_write_reqs_plugged);
     if (s->allocating_acb != NULL) {
         /* Another allocating write came concurrently.  This cannot happen
-         * from bdrv_qed_co_drain, but it can happen when the timer runs.
+         * from bdrv_qed_co_drain_begin, but it can happen when the timer runs.
          */
         qemu_co_mutex_unlock(&s->table_lock);
         return false;
@@ -358,7 +358,7 @@ static void bdrv_qed_attach_aio_context(BlockDriverState *bs,
     }
 }
 
-static void coroutine_fn bdrv_qed_co_drain(BlockDriverState *bs)
+static void coroutine_fn bdrv_qed_co_drain_begin(BlockDriverState *bs)
 {
     BDRVQEDState *s = bs->opaque;
 
@@ -1608,7 +1608,7 @@ static BlockDriver bdrv_qed = {
     .bdrv_check               = bdrv_qed_check,
     .bdrv_detach_aio_context  = bdrv_qed_detach_aio_context,
     .bdrv_attach_aio_context  = bdrv_qed_attach_aio_context,
-    .bdrv_co_drain            = bdrv_qed_co_drain,
+    .bdrv_co_drain_begin      = bdrv_qed_co_drain_begin,
 };
 
 static void bdrv_qed_init(void)
-- 
2.11.0

[Qemu-devel] [PATCH 3/3] block/throttle.c: add bdrv_co_drain_begin/end callbacks

[Manos Pitsidianakis]

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
---
 block/throttle.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/block/throttle.c b/block/throttle.c
index 5bca76300f..833175ac77 100644
--- a/block/throttle.c
+++ b/block/throttle.c
@@ -197,6 +197,21 @@ static bool throttle_recurse_is_first_non_filter(BlockDriverState *bs,
     return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
 }
 
+static void coroutine_fn throttle_co_drain_begin(BlockDriverState *bs)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    if (atomic_fetch_inc(&tgm->io_limits_disabled) == 0) {
+        throttle_group_restart_tgm(tgm);
+    }
+}
+
+static void coroutine_fn throttle_co_drain_end(BlockDriverState *bs)
+{
+    ThrottleGroupMember *tgm = bs->opaque;
+    assert(tgm->io_limits_disabled);
+    atomic_dec(&tgm->io_limits_disabled);
+}
+
 static BlockDriver bdrv_throttle = {
     .format_name                        =   "throttle",
     .protocol_name                      =   "throttle",
@@ -226,6 +241,9 @@ static BlockDriver bdrv_throttle = {
     .bdrv_reopen_abort                  =   throttle_reopen_abort,
     .bdrv_co_get_block_status           =   bdrv_co_get_block_status_from_file,
 
+    .bdrv_co_drain_begin                =   throttle_co_drain_begin,
+    .bdrv_co_drain_end                  =   throttle_co_drain_end,
+
     .is_filter                          =   true,
 };
 
-- 
2.11.0

Re: [Qemu-devel] [PATCH 1/3] block: add bdrv_co_drain_end callback

[Stefan Hajnoczi]

On Wed, Sep 20, 2017 at 01:23:09PM +0300, Manos Pitsidianakis wrote:
> @@ -188,7 +194,7 @@ static bool bdrv_drain_recurse(BlockDriverState *bs)
>      waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
>  
>      /* Ensure any pending metadata writes are submitted to bs->file.  */
> -    bdrv_drain_invoke(bs);
> +    bdrv_drain_invoke(bs, begin);

Do you need to move bdrv_drain_invoke(bs, begin) before
BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0)?

This will ensure that throttling is disabled and the TGM restarted
before we wait for requests to complete.

Stefan

Re: [Qemu-devel] [PATCH 3/3] block/throttle.c: add bdrv_co_drain_begin/end callbacks

[Stefan Hajnoczi]

On Wed, Sep 20, 2017 at 01:23:11PM +0300, Manos Pitsidianakis wrote:
> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
> ---
>  block/throttle.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Re: [Qemu-devel] [PATCH 1/3] block: add bdrv_co_drain_end callback

[Stefan Hajnoczi]

On Wed, Sep 20, 2017 at 01:23:09PM +0300, Manos Pitsidianakis wrote:
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index ba4c383393..ea1326e3c7 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -359,6 +359,8 @@ struct BlockDriver {
>       */
>      void coroutine_fn (*bdrv_co_drain)(BlockDriverState *bs);
>  
> +    void coroutine_fn (*bdrv_co_drain_end)(BlockDriverState *bs);

Please update the doc comment to describe the environment under which
begin() and end() are invoked.  It should be clear when to implement
begin() and/or end().

Re: [Qemu-devel] [PATCH 2/3] block: rename bdrv_co_drain to bdrv_co_drain_begin

[Stefan Hajnoczi]

On Wed, Sep 20, 2017 at 01:23:10PM +0300, Manos Pitsidianakis wrote:
> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
> ---
>  include/block/block_int.h | 2 +-
>  block/io.c                | 4 ++--
>  block/qed.c               | 6 +++---
>  3 files changed, 6 insertions(+), 6 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Re: [Qemu-devel] [PATCH 1/3] block: add bdrv_co_drain_end callback

[Manos Pitsidianakis]

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On Wed, Sep 20, 2017 at 03:26:32PM +0100, Stefan Hajnoczi wrote:
>On Wed, Sep 20, 2017 at 01:23:09PM +0300, Manos Pitsidianakis wrote:
>> @@ -188,7 +194,7 @@ static bool bdrv_drain_recurse(BlockDriverState *bs)
>>      waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
>>
>>      /* Ensure any pending metadata writes are submitted to bs->file.  */
>> -    bdrv_drain_invoke(bs);
>> +    bdrv_drain_invoke(bs, begin);
>
>Do you need to move bdrv_drain_invoke(bs, begin) before
>BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0)?
>
>This will ensure that throttling is disabled and the TGM restarted
>before we wait for requests to complete.
>

Hm yes. Before, the order was irrelevant because BlockBackend issued the 
drain first by restarting the tgm in blk_root_drained_begin.

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