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.
