Am 12.07.2011 09:45, schrieb Markus Armbruster:
> Luiz Capitulino <lcapitul...@redhat.com> writes:
>
>> This commit adds support to the BlockDriverState type to keep track
>> of the last I/O status. That is, at every I/O operation we update
>> a status field in the BlockDriverState instance. Valid statuses are:
>> OK, FAILED and ENOSPC.
>>
>> ENOSPC is distinguished from FAILED because an management application
>> can use it to implement thin-provisioning.
>>
>> This feature has to be explicit enabled by buses/devices supporting it.
>
> buses?
>
>>
>> Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
>> ---
>> block.c | 18 ++++++++++++++++++
>> block.h | 7 +++++++
>> block_int.h | 2 ++
>> 3 files changed, 27 insertions(+), 0 deletions(-)
>>
>> diff --git a/block.c b/block.c
>> index 24a25d5..cc0a34e 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -195,6 +195,7 @@ BlockDriverState *bdrv_new(const char *device_name)
>> if (device_name[0] != '\0') {
>> QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
>> }
>> + bs->iostatus_enabled = false;
>> return bs;
>> }
>>
>> @@ -2876,6 +2877,23 @@ int bdrv_in_use(BlockDriverState *bs)
>> return bs->in_use;
>> }
>>
>> +void bdrv_enable_iostatus(BlockDriverState *bs)
>> +{
>> + bs->iostatus_enabled = true;
>> +}
>> +
>> +void bdrv_iostatus_update(BlockDriverState *bs, int error)
>> +{
>> + error = abs(error);
>> +
>> + if (!error) {
>> + bs->iostatus = BDRV_IOS_OK;
>> + } else {
>> + bs->iostatus = (error == ENOSPC) ? BDRV_IOS_ENOSPC :
>> + BDRV_IOS_FAILED;
>> + }
>> +}
>> +
>> int bdrv_img_create(const char *filename, const char *fmt,
>> const char *base_filename, const char *base_fmt,
>> char *options, uint64_t img_size, int flags)
>> diff --git a/block.h b/block.h
>> index 859d1d9..0dca1bb 100644
>> --- a/block.h
>> +++ b/block.h
>> @@ -50,6 +50,13 @@ typedef enum {
>> BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
>> } BlockMonEventAction;
>>
>> +typedef enum {
>> + BDRV_IOS_OK, BDRV_IOS_FAILED, BDRV_IOS_ENOSPC
>> +} BlockIOStatus;
>> +
>> +void bdrv_iostatus_update(BlockDriverState *bs, int error);
>> +void bdrv_enable_iostatus(BlockDriverState *bs);
>> +void bdrv_enable_io_status(BlockDriverState *bs);
>> void bdrv_mon_event(const BlockDriverState *bdrv,
>> BlockMonEventAction action, int is_read);
>> void bdrv_info_print(Monitor *mon, const QObject *data);
>> diff --git a/block_int.h b/block_int.h
>> index 1e265d2..09f038d 100644
>> --- a/block_int.h
>> +++ b/block_int.h
>> @@ -195,6 +195,8 @@ struct BlockDriverState {
>> drivers. They are not used by the block driver */
>> int cyls, heads, secs, translation;
>> BlockErrorAction on_read_error, on_write_error;
>> + bool iostatus_enabled;
>> + BlockIOStatus iostatus;
>> char device_name[32];
>> unsigned long *dirty_bitmap;
>> int64_t dirty_count;
>
> Okay, let's see what we got here.
>
> The block layer merely holds I/O status, device models set it.
>
> Device I/O status is not migrated. Why?
>
> bdrv_new() creates the BDS with I/O status tracking disabled. Devices
> that do tracking enable it in their qdev init method. If a device gets
> hot unplugged, tracking remains enabled. If the BDS then gets reused
> with a device that doesn't do tracking, I/O status becomes incorrect.
> Can't happen right now, because we automatically delete the BDS on hot
> unplug, but it's a trap. Suggest to disable tracking in bdrv_detach().
>
> Actually, this is a symptom of the midlayer disease. I suspect things
> would be simpler if we hold the status in its rightful owner, the device
> model. Need a getter for it. I'm working on a patch series that moves
> misplaced state out of the block layer into device models and block
> drivers, and a I/O status getter will fit in easily there.
This is host state, so the device is not the rightful owner. Devices
should not even be involved with enabling it.
Kevin
