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block: extend BLOCK_IO_ERROR event with nospace indicator 

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 <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Luiz Capitulino 2014-08-29 16:07:27 -04:00 committed by Kevin Wolf
parent 10601bef56
commit c7c2ff0c7e
2 changed files with 21 additions and 9 deletions
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22
block.c
View File

@ -3639,6 +3639,18 @@ 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).
@ -3664,16 +3676,10 @@ 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);
}
}

8
qapi/block-core.json
View File

@ -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
@ -1587,6 +1588,11 @@
#
# @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
#
@ -1594,7 +1600,7 @@
##
{ 'event': 'BLOCK_IO_ERROR',
'data': { 'device': 'str', 'operation': 'IoOperationType',
'action': 'BlockErrorAction' } }
'action': 'BlockErrorAction', '*nospace': 'bool' } }
##
# @BLOCK_JOB_COMPLETED