[Qemu-devel] [PATCH for-3.1 v3 0/2] block: Fix crash on migration with explicit child nodes

[Qemu-devel] [PATCH for-3.1 v3 0/2] block: Fix crash on migration with explicit child nodes

[Kevin Wolf]

v3:
- Checking whether there are still active parents only really works with
  a single pass, so that's what we do now [Max]
- Test case polishing [Max]

v2:
- Cover children that were created after their parents [Max]

Kevin Wolf (2):
  block: Don't inactivate children before parents
  iotests: Test migration with -blockdev

 block.c                    |  84 +++++++++++++++----------
 tests/qemu-iotests/234     | 121 +++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/234.out |  30 +++++++++
 tests/qemu-iotests/group   |   1 +
 4 files changed, 205 insertions(+), 31 deletions(-)
 create mode 100755 tests/qemu-iotests/234
 create mode 100644 tests/qemu-iotests/234.out

-- 
2.19.1

[Qemu-devel] [PATCH for-3.1 v3 1/2] block: Don't inactivate children before parents

[Kevin Wolf]

bdrv_child_cb_inactivate() asserts that parents are already inactive
when children get inactivated. This precondition is necessary because
parents could still issue requests in their inactivation code.

When block nodes are created individually with -blockdev, all of them
are monitor owned and will be returned by bdrv_next() in an undefined
order (in practice, in the order of their creation, which is usually
children before parents), which obviously fails the assertion:

qemu: block.c:899: bdrv_child_cb_inactivate: Assertion `bs->open_flags & BDRV_O_INACTIVE' failed.

This patch fixes the ordering by skipping nodes with still active
parents in bdrv_inactivate_recurse() because we know that they will be
covered by recursion when the last active parent becomes inactive.

With the correct parents-before-children ordering, we also got rid of
the reason why commit aad0b7a0bfb introduced two passes, so we can go
back to a single-pass recursion. This is necessary so we can rely on the
BDRV_O_INACTIVE flag to skip nodes with active parents (the flag used
to be set only in pass 2, so we would always skip non-root nodes in
pass 1 because all parents would still be considered active; setting the
flag in pass 1 would mean, that we never skip anything in pass 2 because
all parents are already considered inactive).

Because of the change to single pass, this patch is best reviewed with
whitespace changes ignored.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 84 ++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 53 insertions(+), 31 deletions(-)

diff --git a/block.c b/block.c
index 5ba3435f8f..811239ca23 100644
--- a/block.c
+++ b/block.c
@@ -4612,45 +4612,68 @@ void bdrv_invalidate_cache_all(Error **errp)
     }
 }
 
-static int bdrv_inactivate_recurse(BlockDriverState *bs,
-                                   bool setting_flag)
+static bool bdrv_has_bds_parent(BlockDriverState *bs, bool only_active)
+{
+    BdrvChild *parent;
+
+    QLIST_FOREACH(parent, &bs->parents, next_parent) {
+        if (parent->role->parent_is_bds) {
+            BlockDriverState *parent_bs = parent->opaque;
+            if (!only_active || !(parent_bs->open_flags & BDRV_O_INACTIVE)) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+static int bdrv_inactivate_recurse(BlockDriverState *bs)
 {
     BdrvChild *child, *parent;
+    uint64_t perm, shared_perm;
     int ret;
 
     if (!bs->drv) {
         return -ENOMEDIUM;
     }
 
-    if (!setting_flag && bs->drv->bdrv_inactivate) {
+    /* Make sure that we don't inactivate a child before its parent.
+     * It will be covered by recursion from the yet active parent. */
+    if (bdrv_has_bds_parent(bs, true)) {
+        return 0;
+    }
+
+    assert(!(bs->open_flags & BDRV_O_INACTIVE));
+
+    /* Inactivate this node */
+    if (bs->drv->bdrv_inactivate) {
         ret = bs->drv->bdrv_inactivate(bs);
         if (ret < 0) {
             return ret;
         }
     }
 
-    if (setting_flag && !(bs->open_flags & BDRV_O_INACTIVE)) {
-        uint64_t perm, shared_perm;
-
-        QLIST_FOREACH(parent, &bs->parents, next_parent) {
-            if (parent->role->inactivate) {
-                ret = parent->role->inactivate(parent);
-                if (ret < 0) {
-                    return ret;
-                }
+    QLIST_FOREACH(parent, &bs->parents, next_parent) {
+        if (parent->role->inactivate) {
+            ret = parent->role->inactivate(parent);
+            if (ret < 0) {
+                return ret;
             }
         }
+    }
 
-        bs->open_flags |= BDRV_O_INACTIVE;
+    bs->open_flags |= BDRV_O_INACTIVE;
+
+    /* Update permissions, they may differ for inactive nodes */
+    bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
+    bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, &error_abort);
+    bdrv_set_perm(bs, perm, shared_perm);
 
-        /* Update permissions, they may differ for inactive nodes */
-        bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
-        bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, &error_abort);
-        bdrv_set_perm(bs, perm, shared_perm);
-    }
 
+    /* Recursively inactivate children */
     QLIST_FOREACH(child, &bs->children, next) {
-        ret = bdrv_inactivate_recurse(child->bs, setting_flag);
+        ret = bdrv_inactivate_recurse(child->bs);
         if (ret < 0) {
             return ret;
         }
@@ -4664,7 +4687,6 @@ int bdrv_inactivate_all(void)
     BlockDriverState *bs = NULL;
     BdrvNextIterator it;
     int ret = 0;
-    int pass;
     GSList *aio_ctxs = NULL, *ctx;
 
     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
@@ -4676,17 +4698,17 @@ int bdrv_inactivate_all(void)
         }
     }
 
-    /* We do two passes of inactivation. The first pass calls to drivers'
-     * .bdrv_inactivate callbacks recursively so all cache is flushed to disk;
-     * the second pass sets the BDRV_O_INACTIVE flag so that no further write
-     * is allowed. */
-    for (pass = 0; pass < 2; pass++) {
-        for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
-            ret = bdrv_inactivate_recurse(bs, pass);
-            if (ret < 0) {
-                bdrv_next_cleanup(&it);
-                goto out;
-            }
+    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
+        /* Nodes with BDS parents are covered by recursion from the last
+         * parent that gets inactivated. Don't inactivate them a second
+         * time if that has already happened. */
+        if (bdrv_has_bds_parent(bs, false)) {
+            continue;
+        }
+        ret = bdrv_inactivate_recurse(bs);
+        if (ret < 0) {
+            bdrv_next_cleanup(&it);
+            goto out;
         }
     }
 
-- 
2.19.1

[Qemu-devel] [PATCH for-3.1 v3 2/2] iotests: Test migration with -blockdev

[Kevin Wolf]

Check that block node activation and inactivation works with a block
graph that is built with individually created nodes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/qemu-iotests/234     | 121 +++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/234.out |  30 +++++++++
 tests/qemu-iotests/group   |   1 +
 3 files changed, 152 insertions(+)
 create mode 100755 tests/qemu-iotests/234
 create mode 100644 tests/qemu-iotests/234.out

diff --git a/tests/qemu-iotests/234 b/tests/qemu-iotests/234
new file mode 100755
index 0000000000..a8185b4360
--- /dev/null
+++ b/tests/qemu-iotests/234
@@ -0,0 +1,121 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2018 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Creator/Owner: Kevin Wolf <kwolf@redhat.com>
+#
+# Check that block node activation and inactivation works with a block graph
+# that is built with individually created nodes
+
+import iotests
+import os
+
+iotests.verify_image_format(supported_fmts=['qcow2'])
+iotests.verify_platform(['linux'])
+
+with iotests.FilePath('img') as img_path, \
+     iotests.FilePath('backing') as backing_path, \
+     iotests.FilePath('mig_fifo_a') as fifo_a, \
+     iotests.FilePath('mig_fifo_b') as fifo_b, \
+     iotests.VM(path_suffix='a') as vm_a, \
+     iotests.VM(path_suffix='b') as vm_b:
+
+    iotests.qemu_img_pipe('create', '-f', iotests.imgfmt, backing_path, '64M')
+    iotests.qemu_img_pipe('create', '-f', iotests.imgfmt, img_path, '64M')
+
+    os.mkfifo(fifo_a)
+    os.mkfifo(fifo_b)
+
+    iotests.log('Launching source VM...')
+    (vm_a.add_blockdev('file,filename=%s,node-name=drive0-file' % (img_path))
+         .add_blockdev('%s,file=drive0-file,node-name=drive0' % (iotests.imgfmt))
+         .add_blockdev('file,filename=%s,node-name=drive0-backing-file' % (backing_path))
+         .add_blockdev('%s,file=drive0-backing-file,node-name=drive0-backing' % (iotests.imgfmt))
+         .launch())
+
+    iotests.log('Launching destination VM...')
+    (vm_b.add_blockdev('file,filename=%s,node-name=drive0-file' % (img_path))
+         .add_blockdev('%s,file=drive0-file,node-name=drive0' % (iotests.imgfmt))
+         .add_blockdev('file,filename=%s,node-name=drive0-backing-file' % (backing_path))
+         .add_blockdev('%s,file=drive0-backing-file,node-name=drive0-backing' % (iotests.imgfmt))
+         .add_incoming("exec: cat '%s'" % (fifo_a))
+         .launch())
+
+    # Add a child node that was created after the parent node. The reverse case
+    # is covered by the -blockdev options above.
+    iotests.log(vm_a.qmp('blockdev-snapshot', node='drive0-backing',
+                         overlay='drive0'))
+    iotests.log(vm_b.qmp('blockdev-snapshot', node='drive0-backing',
+                         overlay='drive0'))
+
+    iotests.log('Enabling migration QMP events on A...')
+    iotests.log(vm_a.qmp('migrate-set-capabilities', capabilities=[
+        {
+            'capability': 'events',
+            'state': True
+        }
+    ]))
+
+    iotests.log('Starting migration to B...')
+    iotests.log(vm_a.qmp('migrate', uri='exec:cat >%s' % (fifo_a)))
+    with iotests.Timeout(3, 'Migration does not complete'):
+        while True:
+            event = vm_a.event_wait('MIGRATION')
+            iotests.log(event, filters=[iotests.filter_qmp_event])
+            if event['data']['status'] == 'completed':
+                break
+
+    iotests.log(vm_a.qmp('query-migrate')['return']['status'])
+    iotests.log(vm_b.qmp('query-migrate')['return']['status'])
+
+    iotests.log(vm_a.qmp('query-status'))
+    iotests.log(vm_b.qmp('query-status'))
+
+    iotests.log('Add a second parent to drive0-file...')
+    iotests.log(vm_b.qmp('blockdev-add', driver='raw', file='drive0-file',
+                         node_name='drive0-raw'))
+
+    iotests.log('Restart A with -incoming and second parent...')
+    vm_a.shutdown()
+    (vm_a.add_blockdev('raw,file=drive0-file,node-name=drive0-raw')
+         .add_incoming("exec: cat '%s'" % (fifo_b))
+         .launch())
+
+    iotests.log(vm_a.qmp('blockdev-snapshot', node='drive0-backing',
+                         overlay='drive0'))
+
+    iotests.log('Enabling migration QMP events on B...')
+    iotests.log(vm_b.qmp('migrate-set-capabilities', capabilities=[
+        {
+            'capability': 'events',
+            'state': True
+        }
+    ]))
+
+    iotests.log('Starting migration back to A...')
+    iotests.log(vm_b.qmp('migrate', uri='exec:cat >%s' % (fifo_b)))
+    with iotests.Timeout(3, 'Migration does not complete'):
+        while True:
+            event = vm_b.event_wait('MIGRATION')
+            iotests.log(event, filters=[iotests.filter_qmp_event])
+            if event['data']['status'] == 'completed':
+                break
+
+    iotests.log(vm_a.qmp('query-migrate')['return']['status'])
+    iotests.log(vm_b.qmp('query-migrate')['return']['status'])
+
+    iotests.log(vm_a.qmp('query-status'))
+    iotests.log(vm_b.qmp('query-status'))
diff --git a/tests/qemu-iotests/234.out b/tests/qemu-iotests/234.out
new file mode 100644
index 0000000000..b9ed910b1a
--- /dev/null
+++ b/tests/qemu-iotests/234.out
@@ -0,0 +1,30 @@
+Launching source VM...
+Launching destination VM...
+{"return": {}}
+{"return": {}}
+Enabling migration QMP events on A...
+{"return": {}}
+Starting migration to B...
+{"return": {}}
+{"data": {"status": "setup"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"data": {"status": "active"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"data": {"status": "completed"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+completed
+completed
+{"return": {"running": false, "singlestep": false, "status": "postmigrate"}}
+{"return": {"running": true, "singlestep": false, "status": "running"}}
+Add a second parent to drive0-file...
+{"return": {}}
+Restart A with -incoming and second parent...
+{"return": {}}
+Enabling migration QMP events on B...
+{"return": {}}
+Starting migration back to A...
+{"return": {}}
+{"data": {"status": "setup"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"data": {"status": "active"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"data": {"status": "completed"}, "event": "MIGRATION", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+completed
+completed
+{"return": {"running": true, "singlestep": false, "status": "running"}}
+{"return": {"running": false, "singlestep": false, "status": "postmigrate"}}
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index ddf1a5b549..8c56a0ad11 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -231,3 +231,4 @@
 231 auto quick
 232 auto quick
 233 auto quick
+234 auto quick migration
-- 
2.19.1

Re: [Qemu-devel] [PATCH for-3.1 v3 0/2] block: Fix crash on migration with explicit child nodes

[Max Reitz]

[-- Attachment #1: Type: text/plain, Size: 826 bytes --]

On 26.11.18 17:05, Kevin Wolf wrote:
> v3:
> - Checking whether there are still active parents only really works with
>   a single pass, so that's what we do now [Max]
> - Test case polishing [Max]
> 
> v2:
> - Cover children that were created after their parents [Max]
> 
> Kevin Wolf (2):
>   block: Don't inactivate children before parents
>   iotests: Test migration with -blockdev
> 
>  block.c                    |  84 +++++++++++++++----------
>  tests/qemu-iotests/234     | 121 +++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/234.out |  30 +++++++++
>  tests/qemu-iotests/group   |   1 +
>  4 files changed, 205 insertions(+), 31 deletions(-)
>  create mode 100755 tests/qemu-iotests/234
>  create mode 100644 tests/qemu-iotests/234.out

Reviewed-by: Max Reitz <mreitz@redhat.com>


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