On 04.09.23 11:31, Andrey Zhadchenko wrote:
Unlike other transaction commands, bitmap operations do not drain target
bds. If we have an IOThread, this may result in some inconsistencies, as
bitmap content may change during transaction command.
Add bdrv_drained_begin()/end() to bitmap operations.
Signed-off-by: Andrey Zhadchenko<andrey.zhadche...@virtuozzo.com>
Hi!
First, please always include cover letter when more than 1 patch.
Next. Hmm. Good idea, but I'm afraid that's still not enough.
Assume you have two BSs A and B in two different iothreads. So, the sequence
may be like this:
1. drain_begin A
2. do operation with bitmap in A
3. guest writes to B, B is modified and bitmap in B is modified as well
4. drain_begin B
5. do operation with bitmap in B
6. drain_end B
7. drain_end A
User may expect, that all the operations are done atomically in relation to any
guest IO operations. And if operations are dependent, the intermediate write
[3] make break the result.
So, we should drain all participant drives during the whole transactions. The
simplest solution is bdrv_drain_all_begin() / bdrv_drain_all_end() pair in
qmp_transaction(), could we start with it?
--
Best regards,
Vladimir
