[Qemu-devel] [PULL for-2.11-rc2 0/5] Block patches

[Qemu-devel] [PULL for-2.11-rc2 0/5] Block patches

[Stefan Hajnoczi]

The following changes since commit 508ba0f7e2092d3ca56e3f75e894d52d8b94818e:

  Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20171109' into staging (2017-11-13 11:41:47 +0000)

are available in the git repository at:

  git://github.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to 0761562687e0d8135310a94b1d3e08376387c027:

  qemu-iotests: Test I/O limits with removable media (2017-11-13 15:46:26 +0000)

----------------------------------------------------------------
Pull request

The following disk I/O throttling fixes solve recent bugs.

----------------------------------------------------------------

Alberto Garcia (3):
  block: Check for inserted BlockDriverState in blk_io_limits_disable()
  block: Leave valid throttle timers when removing a BDS from a backend
  qemu-iotests: Test I/O limits with removable media

Stefan Hajnoczi (1):
  throttle-groups: drain before detaching ThrottleState

Zhengui (1):
  block: all I/O should be completed before removing throttle timers.

 block/block-backend.c      | 36 ++++++++++++++++++---------
 block/throttle-groups.c    |  6 +++++
 tests/qemu-iotests/093     | 62 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/093.out |  4 +--
 4 files changed, 94 insertions(+), 14 deletions(-)

-- 
2.13.6

[Qemu-devel] [PULL for-2.11-rc2 1/5] block: all I/O should be completed before removing throttle timers.

[Stefan Hajnoczi]

From: Zhengui <lizhengui@huawei.com>

In blk_remove_bs, all I/O should be completed before removing throttle
timers. If there has inflight I/O, removing throttle timers here will
cause the inflight I/O never return.
This patch add bdrv_drained_begin before throttle_timers_detach_aio_context
to let all I/O completed before removing throttle timers.

[Moved declaration of bs as suggested by Alberto Garcia
<berto@igalia.com>.
--Stefan]

Signed-off-by: Zhengui <lizhengui@huawei.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 1508564040-120700-1-git-send-email-lizhengui@huawei.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/block-backend.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 45d9101be3..18e543780d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -655,12 +655,16 @@ BlockBackend *blk_by_public(BlockBackendPublic *public)
  */
 void blk_remove_bs(BlockBackend *blk)
 {
+    BlockDriverState *bs;
     ThrottleTimers *tt;
 
     notifier_list_notify(&blk->remove_bs_notifiers, blk);
     if (blk->public.throttle_group_member.throttle_state) {
         tt = &blk->public.throttle_group_member.throttle_timers;
+        bs = blk_bs(blk);
+        bdrv_drained_begin(bs);
         throttle_timers_detach_aio_context(tt);
+        bdrv_drained_end(bs);
     }
 
     blk_update_root_state(blk);
-- 
2.13.6

[Qemu-devel] [PULL for-2.11-rc2 2/5] throttle-groups: drain before detaching ThrottleState

[Stefan Hajnoczi]

I/O requests hang after stop/cont commands at least since QEMU 2.10.0
with -drive iops=100:

  (guest)$ dd if=/dev/zero of=/dev/vdb oflag=direct count=1000
  (qemu) stop
  (qemu) cont
  ...I/O is stuck...

This happens because blk_set_aio_context() detaches the ThrottleState
while requests may still be in flight:

  if (tgm->throttle_state) {
      throttle_group_detach_aio_context(tgm);
      throttle_group_attach_aio_context(tgm, new_context);
  }

This patch encloses the detach/attach calls in a drained region so no
I/O request is left hanging.  Also add assertions so we don't make the
same mistake again in the future.

Reported-by: Yongxue Hong <yhong@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20171110151934.16883-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/block-backend.c   | 2 ++
 block/throttle-groups.c | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 18e543780d..ab75da32c9 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1752,8 +1752,10 @@ void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
 
     if (bs) {
         if (tgm->throttle_state) {
+            bdrv_drained_begin(bs);
             throttle_group_detach_aio_context(tgm);
             throttle_group_attach_aio_context(tgm, new_context);
+            bdrv_drained_end(bs);
         }
         bdrv_set_aio_context(bs, new_context);
     }
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
index b291a88481..2587f19ca3 100644
--- a/block/throttle-groups.c
+++ b/block/throttle-groups.c
@@ -594,6 +594,12 @@ void throttle_group_attach_aio_context(ThrottleGroupMember *tgm,
 void throttle_group_detach_aio_context(ThrottleGroupMember *tgm)
 {
     ThrottleTimers *tt = &tgm->throttle_timers;
+
+    /* Requests must have been drained */
+    assert(tgm->pending_reqs[0] == 0 && tgm->pending_reqs[1] == 0);
+    assert(qemu_co_queue_empty(&tgm->throttled_reqs[0]));
+    assert(qemu_co_queue_empty(&tgm->throttled_reqs[1]));
+
     throttle_timers_detach_aio_context(tt);
     tgm->aio_context = NULL;
 }
-- 
2.13.6

[Qemu-devel] [PULL for-2.11-rc2 3/5] block: Check for inserted BlockDriverState in blk_io_limits_disable()

[Stefan Hajnoczi]

From: Alberto Garcia <berto@igalia.com>

When you set I/O limits using block_set_io_throttle or the command
line throttling.* options they are kept in the BlockBackend regardless
of whether a BlockDriverState is attached to the backend or not.

Therefore when removing the limits using blk_io_limits_disable() we
need to check if there's a BDS before attempting to drain it, else it
will crash QEMU. This can be reproduced very easily using HMP:

     (qemu) drive_add 0 if=none,throttling.iops-total=5000
     (qemu) drive_del none0

Reported-by: sochin jiang <sochin.jiang@huawei.com>
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 0d3a67ce8d948bb33e08672564714dcfb76a3d8c.1510339534.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/block-backend.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index ab75da32c9..df92a6280d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1980,10 +1980,16 @@ void blk_set_io_limits(BlockBackend *blk, ThrottleConfig *cfg)
 
 void blk_io_limits_disable(BlockBackend *blk)
 {
-    assert(blk->public.throttle_group_member.throttle_state);
-    bdrv_drained_begin(blk_bs(blk));
-    throttle_group_unregister_tgm(&blk->public.throttle_group_member);
-    bdrv_drained_end(blk_bs(blk));
+    BlockDriverState *bs = blk_bs(blk);
+    ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
+    assert(tgm->throttle_state);
+    if (bs) {
+        bdrv_drained_begin(bs);
+    }
+    throttle_group_unregister_tgm(tgm);
+    if (bs) {
+        bdrv_drained_end(bs);
+    }
 }
 
 /* should be called before blk_set_io_limits if a limit is set */
-- 
2.13.6

[Qemu-devel] [PULL for-2.11-rc2 4/5] block: Leave valid throttle timers when removing a BDS from a backend

[Stefan Hajnoczi]

From: Alberto Garcia <berto@igalia.com>

If a BlockBackend has I/O limits set then its ThrottleGroupMember
structure uses the AioContext from its attached BlockDriverState.
Those two contexts must be kept in sync manually. This is not
ideal and will be fixed in the future by removing the throttling
configuration from the BlockBackend and storing it in an implicit
filter node instead, but for now we have to live with this.

When you remove the BlockDriverState from the backend then the
throttle timers are destroyed. If a new BlockDriverState is later
inserted then they are created again using the new AioContext.

There are a couple of problems with this:

   a) The code manipulates the timers directly, leaving the
      ThrottleGroupMember.aio_context field in an inconsisent state.

   b) If you remove the I/O limits (e.g by destroying the backend)
      when the timers are gone then throttle_group_unregister_tgm()
      will attempt to destroy them again, crashing QEMU.

While b) could be fixed easily by allowing the timers to be freed
twice, this would result in a situation in which we can no longer
guarantee that a valid ThrottleState has a valid AioContext and
timers.

This patch ensures that the timers and AioContext are always valid
when I/O limits are set, regardless of whether the BlockBackend has a
BlockDriverState inserted or not.

[Fixed "There'a" typo as suggested by Max Reitz <mreitz@redhat.com>
--Stefan]

Reported-by: sochin jiang <sochin.jiang@huawei.com>
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: e089c66e7c20289b046d782cea4373b765c5bc1d.1510339534.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/block-backend.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index df92a6280d..f10b1db612 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -655,15 +655,15 @@ BlockBackend *blk_by_public(BlockBackendPublic *public)
  */
 void blk_remove_bs(BlockBackend *blk)
 {
+    ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
     BlockDriverState *bs;
-    ThrottleTimers *tt;
 
     notifier_list_notify(&blk->remove_bs_notifiers, blk);
-    if (blk->public.throttle_group_member.throttle_state) {
-        tt = &blk->public.throttle_group_member.throttle_timers;
+    if (tgm->throttle_state) {
         bs = blk_bs(blk);
         bdrv_drained_begin(bs);
-        throttle_timers_detach_aio_context(tt);
+        throttle_group_detach_aio_context(tgm);
+        throttle_group_attach_aio_context(tgm, qemu_get_aio_context());
         bdrv_drained_end(bs);
     }
 
@@ -678,6 +678,7 @@ void blk_remove_bs(BlockBackend *blk)
  */
 int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp)
 {
+    ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
     blk->root = bdrv_root_attach_child(bs, "root", &child_root,
                                        blk->perm, blk->shared_perm, blk, errp);
     if (blk->root == NULL) {
@@ -686,10 +687,9 @@ int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp)
     bdrv_ref(bs);
 
     notifier_list_notify(&blk->insert_bs_notifiers, blk);
-    if (blk->public.throttle_group_member.throttle_state) {
-        throttle_timers_attach_aio_context(
-            &blk->public.throttle_group_member.throttle_timers,
-            bdrv_get_aio_context(bs));
+    if (tgm->throttle_state) {
+        throttle_group_detach_aio_context(tgm);
+        throttle_group_attach_aio_context(tgm, bdrv_get_aio_context(bs));
     }
 
     return 0;
-- 
2.13.6

[Qemu-devel] [PULL for-2.11-rc2 5/5] qemu-iotests: Test I/O limits with removable media

[Stefan Hajnoczi]

From: Alberto Garcia <berto@igalia.com>

This test hotplugs a CD drive to a VM and checks that I/O limits can
be set only when the drive has media inserted and that they are kept
when the media is replaced.

This also tests the removal of a device with valid I/O limits set but
no media inserted. This involves deleting and disabling the limits
of a BlockBackend without BlockDriverState, a scenario that has been
crashing until the fixes from the last couple of patches.

[Python PEP8 fixup: "Don't use spaces are the = sign when used to
indicate a keyword argument or a default parameter value"
--Stefan]

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 071eb397118ed207c5a7f01d58766e415ee18d6a.1510339534.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/093     | 62 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/093.out |  4 +--
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/tests/qemu-iotests/093 b/tests/qemu-iotests/093
index ef3997206b..5c36a5fb4d 100755
--- a/tests/qemu-iotests/093
+++ b/tests/qemu-iotests/093
@@ -308,6 +308,68 @@ class ThrottleTestGroupNames(iotests.QMPTestCase):
             groupname = "group%d" % i
             self.verify_name(devname, groupname)
 
+class ThrottleTestRemovableMedia(iotests.QMPTestCase):
+    def setUp(self):
+        self.vm = iotests.VM()
+        if iotests.qemu_default_machine == 's390-ccw-virtio':
+            self.vm.add_device("virtio-scsi-ccw,id=virtio-scsi")
+        else:
+            self.vm.add_device("virtio-scsi-pci,id=virtio-scsi")
+        self.vm.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+
+    def test_removable_media(self):
+        # Add a couple of dummy nodes named cd0 and cd1
+        result = self.vm.qmp("blockdev-add", driver="null-aio",
+                             node_name="cd0")
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp("blockdev-add", driver="null-aio",
+                             node_name="cd1")
+        self.assert_qmp(result, 'return', {})
+
+        # Attach a CD drive with cd0 inserted
+        result = self.vm.qmp("device_add", driver="scsi-cd",
+                             id="dev0", drive="cd0")
+        self.assert_qmp(result, 'return', {})
+
+        # Set I/O limits
+        args = { "id": "dev0", "iops": 100, "iops_rd": 0, "iops_wr": 0,
+                                "bps":  50,  "bps_rd": 0,  "bps_wr": 0 }
+        result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **args)
+        self.assert_qmp(result, 'return', {})
+
+        # Check that the I/O limits have been set
+        result = self.vm.qmp("query-block")
+        self.assert_qmp(result, 'return[0]/inserted/iops', 100)
+        self.assert_qmp(result, 'return[0]/inserted/bps',   50)
+
+        # Now eject cd0 and insert cd1
+        result = self.vm.qmp("blockdev-open-tray", id='dev0')
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp("x-blockdev-remove-medium", id='dev0')
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp("x-blockdev-insert-medium", id='dev0', node_name='cd1')
+        self.assert_qmp(result, 'return', {})
+
+        # Check that the I/O limits are still the same
+        result = self.vm.qmp("query-block")
+        self.assert_qmp(result, 'return[0]/inserted/iops', 100)
+        self.assert_qmp(result, 'return[0]/inserted/bps',   50)
+
+        # Eject cd1
+        result = self.vm.qmp("x-blockdev-remove-medium", id='dev0')
+        self.assert_qmp(result, 'return', {})
+
+        # Check that we can't set limits if the device has no medium
+        result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **args)
+        self.assert_qmp(result, 'error/class', 'GenericError')
+
+        # Remove the CD drive
+        result = self.vm.qmp("device_del", id='dev0')
+        self.assert_qmp(result, 'return', {})
+
 
 if __name__ == '__main__':
     iotests.main(supported_fmts=["raw"])
diff --git a/tests/qemu-iotests/093.out b/tests/qemu-iotests/093.out
index 2f7d3902f2..594c16f49f 100644
--- a/tests/qemu-iotests/093.out
+++ b/tests/qemu-iotests/093.out
@@ -1,5 +1,5 @@
-.......
+........
 ----------------------------------------------------------------------
-Ran 7 tests
+Ran 8 tests
 
 OK
-- 
2.13.6

Re: [Qemu-devel] [PULL for-2.11-rc2 0/5] Block patches

[Peter Maydell]

On 14 November 2017 at 10:37, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> The following changes since commit 508ba0f7e2092d3ca56e3f75e894d52d8b94818e:
>
>   Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20171109' into staging (2017-11-13 11:41:47 +0000)
>
> are available in the git repository at:
>
>   git://github.com/stefanha/qemu.git tags/block-pull-request
>
> for you to fetch changes up to 0761562687e0d8135310a94b1d3e08376387c027:
>
>   qemu-iotests: Test I/O limits with removable media (2017-11-13 15:46:26 +0000)
>
> ----------------------------------------------------------------
> Pull request
>
> The following disk I/O throttling fixes solve recent bugs.

Applied, thanks.

-- PMM