Re: [PATCH v3 0/6] block-status cache for data regions

[Hanna Reitz]

On 12.08.21 10:41, Hanna Reitz wrote:
> Hi,
>
> See the cover letter from v1 for the general idea:
> https://lists.nongnu.org/archive/html/qemu-block/2021-06/msg00843.html
>
> Cover letter from v2, introducing RCU locking:
> https://lists.nongnu.org/archive/html/qemu-block/2021-06/msg01060.html
>
>
> v3:
> - Patch 2:
>    - Add rcu_head object to BdrvBlockStatusCache, so we can use
>      g_free_rcu() to free it instead of synchronize_rcu()+g_free()
>    - Use qatomic_rcu_read() every time we read bs->block_status_cache
>      (except in bdrv_close(), where no concurrency is possible)
>    - Use RCU_READ_LOCK_GUARD() instead of WITH_RCU_READ_LOCK_GUARD() in
>      functions where we lock the whole scope anyway
>    - Same for QEMU_LOCK_GUARD() instead of WITH_QEMU_LOCK_GUARD() in
>      bdrv_bsc_fill()
>    - Drop from_cache variable in bdrv_co_block_status()
>      (was an artifact from v1, which had a different control flow and
>      needed this variable)
>    - Assert that local_map returned from a protocol driver’s
>      bdrv_co_block_status() implementation is equal to the offset we
>      passed to it (see comment there for why we should do this)
>
> - Patch 3:
>    - Add note why block drivers should return larger *pnum values in
>      addition to just saying that it’s allowed

Thanks for the reviews, I’ve added the `local_file == bs` assertion in 
patch 2 as suggested by Vladimir (and updated the comment to match) and 
applied the series to my block branch:

https://github.com/XanClic/qemu/commits/block

Hanna