Management software, such as RHEV's vdsm, want to be able to allocate
disk space on demand. The basic use case is to start a VM with a small
disk and then the disk is enlarged when QEMU hits a ENOSPC condition.
To this end, the management software has to be notified when QEMU
encounters ENOSPC. The solution implemented by this commit is simple:
it extends the BLOCK_IO_ERROR with a 'nospace' key, which is true
when QEMU is stopped due to ENOSPC.
Note that support for querying this event is already present in
query-block by means of the 'io-status' key. Also, the new 'nospace'
BLOCK_IO_ERROR field shares the same semantics with 'io-status',
which basically means that werror= has to be set to either
'stop' or 'enospc' to enable 'nospace'.
Finally, this commit also updates the 'io-status' key doc in the
schema with a list of supported device models.
Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
---
Three important observations:
1. We've talked with oVirt and OpenStack folks. oVirt folks say that
this implementation is enough for their use-case. OpenStack don't
need this feature
2. While testing this with a raw image on a (smaller) ext2 file mounted
via the loopback device, I get half "Invalid argument" I/O errors and
half "No space" errors". This means that half of the BLOCK_IO_ERROR
events that are emitted for this test-case will have nospace=false
and the other half nospace=true. I don't know why I'm getting those
"Invalid argument" errors, can anyone of the block layer comment
on this? I don't get that with a qcow2 image (I get nospace=true for
all events)
3. I think this should go via block tree
block.c | 22 ++++++++++++++--------
qapi/block-core.json | 8 +++++++-
2 files changed, 21 insertions(+), 9 deletions(-)
diff --git a/block.c b/block.c
index 1df13ac..b334e35 100644
--- a/block.c
+++ b/block.c
@@ -3632,6 +3632,18 @@ BlockErrorAction bdrv_get_error_action(BlockDriverState
*bs, bool is_read, int e
}
}
+static void send_qmp_error_event(BlockDriverState *bs,
+ BlockErrorAction action,
+ bool is_read, int error)
+{
+ BlockErrorAction ac;
+
+ ac = is_read ? IO_OPERATION_TYPE_READ : IO_OPERATION_TYPE_WRITE;
+ qapi_event_send_block_io_error(bdrv_get_device_name(bs), ac, action,
+ bdrv_iostatus_is_enabled(bs),
+ error == ENOSPC, &error_abort);
+}
+
/* This is done by device models because, while the block layer knows
* about the error, it does not know whether an operation comes from
* the device or the block layer (from a job, for example).
@@ -3657,16 +3669,10 @@ void bdrv_error_action(BlockDriverState *bs,
BlockErrorAction action,
* also ensures that the STOP/RESUME pair of events is emitted.
*/
qemu_system_vmstop_request_prepare();
- qapi_event_send_block_io_error(bdrv_get_device_name(bs),
- is_read ? IO_OPERATION_TYPE_READ :
- IO_OPERATION_TYPE_WRITE,
- action, &error_abort);
+ send_qmp_error_event(bs, action, is_read, error);
qemu_system_vmstop_request(RUN_STATE_IO_ERROR);
} else {
- qapi_event_send_block_io_error(bdrv_get_device_name(bs),
- is_read ? IO_OPERATION_TYPE_READ :
- IO_OPERATION_TYPE_WRITE,
- action, &error_abort);
+ send_qmp_error_event(bs, action, is_read, error);
}
}
diff --git a/qapi/block-core.json b/qapi/block-core.json
index fb74c56..567e0a6 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -336,6 +336,7 @@
#
# @io-status: #optional @BlockDeviceIoStatus. Only present if the device
# supports it and the VM is configured to stop on errors
+# (supported device models: virtio-blk, ide, scsi-disk)
#
# @inserted: #optional @BlockDeviceInfo describing the device if media is
# present
@@ -1569,6 +1570,11 @@
#
# @action: action that has been taken
#
+# @nospace: #optional true if I/O error was caused due to a no-space
+# condition. This key is only present if query-block's
+# io-status is present, please see query-block documentation
+# for more information (since: 2.2)
+#
# Note: If action is "stop", a STOP event will eventually follow the
# BLOCK_IO_ERROR event
#
@@ -1576,7 +1582,7 @@
##
{ 'event': 'BLOCK_IO_ERROR',
'data': { 'device': 'str', 'operation': 'IoOperationType',
- 'action': 'BlockErrorAction' } }
+ 'action': 'BlockErrorAction', '*nospace': 'bool' } }
##
# @BLOCK_JOB_COMPLETED
--
1.9.3
