Re: [Qemu-block] [PATCH v7 00/10] block: Protect nested event loop with bdrv_drained_begin and bdrv_drained_end

[Stefan Hajnoczi]

On Fri, Oct 23, 2015 at 11:08:04AM +0800, Fam Zheng wrote:
> v7: Exclude bdrv_drain and bdrv_qed_drain patches, they'll follow the
>     bdrv_drain fix for bdrv_aio_flush.
>     Fix internal snapshot clean.
> 
> v6: Add Kevin's rev-by in patches 1-3, 6-8, 10, 12.
>     Add Jeff's rev-by in patches 1, 2, 6-8, 10.
>     04: Fix spelling and wording in comments. [Jeff]
>         Add assert at decrement. [Jeff]
>     05: Fix bad rebase. [Jeff]
>     09: Let blk_is_available come first. [Jeff, Kevin]
>     11: Rewrite bdrv_qed_drain. [Jeff]
> 
> v5: Rebase onto Kevin's block tree.
> 
> v4: Rebase on to master so fix the "bdrv_move_feature_fields" issue.
> 
> v3: Call bdrv_drain unconditionally in bdrv_drained_begin.
>     Document the internal I/O implications between bdrv_drain_begin and end.
> 
> The nested aio_poll()'s in block layer has a bug that new r/w requests from
> ioeventfds and nbd exports are processed, which might break the caller's
> semantics (qmp_transaction) or even pointers (bdrv_reopen).

Probably not worth the hassle of renaming things, but this reminds me of
maskable interrupts.  When interrupts are masked, they are not
delivered.  Same thing here for file descriptors and I think a bool
maskable flag would be a bit more self-explanatory than bool
is_external.