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block: extend BLOCK_IO_ERROR event with nospace indicator

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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
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@ -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);
}
}