On Wed, Oct 21, 2015 at 10:06:46AM +0800, Fam Zheng wrote:
> This ensures the atomicity of the transaction by avoiding processing of
> external requests such as those from ioeventfd.
>
> state->bs is assigned right after bdrv_drained_begin. Because it was
> used as the flag for deletion or not in abort, now we need a separate
> flag - InternalSnapshotState.created.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> blockdev.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/blockdev.c b/blockdev.c
> index 52f44b2..92c2d0d 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1370,6 +1370,7 @@ typedef struct InternalSnapshotState {
> BlockDriverState *bs;
> AioContext *aio_context;
> QEMUSnapshotInfo sn;
> + bool created;
> } InternalSnapshotState;
>
> static void internal_snapshot_prepare(BlkTransactionState *common,
> @@ -1407,6 +1408,8 @@ static void
> internal_snapshot_prepare(BlkTransactionState *common,
> /* AioContext is released in .clean() */
> state->aio_context = blk_get_aio_context(blk);
> aio_context_acquire(state->aio_context);
> + state->bs = blk_bs(blk);
> + bdrv_drained_begin(state->bs);
>
Do you think it'd make sense to move the context acquisition & call to
bdrv_drained_begin() below the check for blk_is_available()? That way
the assignment of state->bs doesn't happen until after the call to
blk_is_available(). It looks like state->created protects us either
way, though - but if blk_is_inserted() fails, then there is no need
for _abort or _clean to do anything, if we hold off on grabbing the
context.
I think I am fine with it as is though, too.
> if (!blk_is_available(blk)) {
> error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
> @@ -1465,7 +1468,7 @@ static void
> internal_snapshot_prepare(BlkTransactionState *common,
> }
>
> /* 4. succeed, mark a snapshot is created */
> - state->bs = bs;
> + state->created = true;
> }
>
> static void internal_snapshot_abort(BlkTransactionState *common)
> @@ -1476,7 +1479,7 @@ static void internal_snapshot_abort(BlkTransactionState
> *common)
> QEMUSnapshotInfo *sn = &state->sn;
> Error *local_error = NULL;
>
> - if (!bs) {
> + if (!state->created) {
> return;
> }
>
> @@ -1497,6 +1500,7 @@ static void internal_snapshot_clean(BlkTransactionState
> *common)
> common, common);
>
> if (state->aio_context) {
> + bdrv_drained_end(state->bs);
> aio_context_release(state->aio_context);
> }
> }
> --
> 2.4.3
>
>
