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block: bdrv_reopen() with backing file in different AioContext 

This patch allows bdrv_reopen() (and therefore the x-blockdev-reopen QMP
command) to attach a node as the new backing file even if the node is in
a different AioContext than the parent if one of both nodes can be moved
to the AioContext of the other node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <20200306141413.30705-3-kwolf@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2020-03-06 15:14:13 +01:00
parent 97518e11c3
commit 1de6b45fb5
2 changed files with 29 additions and 11 deletions
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32
block.c
View File

@ -3787,6 +3787,29 @@ static void bdrv_reopen_perm(BlockReopenQueue *q, BlockDriverState *bs,
*shared = cumulative_shared_perms;
}
static bool bdrv_reopen_can_attach(BlockDriverState *parent,
BdrvChild *child,
BlockDriverState *new_child,
Error **errp)
{
AioContext *parent_ctx = bdrv_get_aio_context(parent);
AioContext *child_ctx = bdrv_get_aio_context(new_child);
GSList *ignore;
bool ret;
ignore = g_slist_prepend(NULL, child);
ret = bdrv_can_set_aio_context(new_child, parent_ctx, &ignore, NULL);
g_slist_free(ignore);
if (ret) {
return ret;
}
ignore = g_slist_prepend(NULL, child);
ret = bdrv_can_set_aio_context(parent, child_ctx, &ignore, errp);
g_slist_free(ignore);
return ret;
}
/*
* Take a BDRVReopenState and check if the value of 'backing' in the
* reopen_state->options QDict is valid or not.
@ -3838,14 +3861,11 @@ static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
}
/*
* TODO: before removing the x- prefix from x-blockdev-reopen we
* should move the new backing file into the right AioContext
* instead of returning an error.
* Check AioContext compatibility so that the bdrv_set_backing_hd() call in
* bdrv_reopen_commit() won't fail.
*/
if (new_backing_bs) {
if (bdrv_get_aio_context(new_backing_bs) != bdrv_get_aio_context(bs)) {
error_setg(errp, "Cannot use a new backing file "
"with a different AioContext");
if (!bdrv_reopen_can_attach(bs, bs->backing, new_backing_bs, errp)) {
return -EINVAL;
}
}

8
tests/qemu-iotests/245
View File

@ -1015,18 +1015,16 @@ class TestBlockdevReopen(iotests.QMPTestCase):
# neither of them can switch to the other AioContext
def test_iothreads_error(self):
self.run_test_iothreads('iothread0', 'iothread1',
"Cannot use a new backing file with a different AioContext")
"Cannot change iothread of active block backend")
def test_iothreads_compatible_users(self):
self.run_test_iothreads('iothread0', 'iothread0')
def test_iothreads_switch_backing(self):
self.run_test_iothreads('iothread0', None,
"Cannot use a new backing file with a different AioContext")
self.run_test_iothreads('iothread0', None)
def test_iothreads_switch_overlay(self):
self.run_test_iothreads(None, 'iothread0',
"Cannot use a new backing file with a different AioContext")
self.run_test_iothreads(None, 'iothread0')
if __name__ == '__main__':
iotests.main(supported_fmts=["qcow2"],