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Re: [Qemu-devel] [PATCH v2 00/20] Drain fixes and cleanups, part 3
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH v2 00/20] Drain fixes and cleanups, part 3 |
Date: |
Mon, 11 Jun 2018 14:23:14 +0200 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
ping?
Am 29.05.2018 um 19:21 hat Kevin Wolf geschrieben:
> This is the third and hopefully for now last part of my work to fix
> drain. The main goal of this series is to make drain robust against
> graph changes that happen in any callbacks of in-flight requests while
> we drain a block node.
>
> The individual patches describe the details, but the rough plan is to
> change all three drain types (single node, subtree and all) to work like
> this:
>
> 1. First call all the necessary callbacks to quiesce external sources
> for new requests. This includes the block driver callbacks, the child
> node callbacks and disabling external AioContext events. This is done
> recursively.
>
> Much of the trouble we had with drain resulted from the fact that the
> graph changed while we were traversing the graph recursively. None of
> the callbacks called in this phase may change the graph.
>
> 2. Then do a single AIO_WAIT_WHILE() to drain the requests of all
> affected nodes. The aio_poll() called by it is where graph changes
> can happen and we need to be careful.
>
> However, while evaluating the loop condition, the graph can't change,
> so we can safely call all necessary callbacks, if needed recursively,
> to determine whether there are still pending requests in any affected
> nodes. We just need to make sure that we don't rely on the set of
> nodes being the same between any two evaluation of the condition.
>
> There are a few more smaller, mostly self-contained changes needed
> before we're actually safe, but this is the main mechanism that will
> help you understand what we're working towards during the series.
>
> v2:
>
> - Rebased on top of current master (e.g. including Job infrastructure)
>
> - Avoid unnecessary parent callbacks for .drained_begin/poll/end:
> * subtree drains: Don't propagate the drain to the parent that we came
> from recursively
> * drain_all: Don't propagate the drain to BDS parents (which are
> already separately drained), but only to non-BDS
> parents like BBs or Jobs
>
> - Separate bdrv_drain_poll_top_level() function instead of having a
> top_level parameter for bdrv_drain_poll().
>
> - A few commit message and comment improvements
>
>
> Kevin Wolf (19):
> test-bdrv-drain: bdrv_drain() works with cross-AioContext events
> block: Use bdrv_do_drain_begin/end in bdrv_drain_all()
> block: Remove 'recursive' parameter from bdrv_drain_invoke()
> block: Don't manually poll in bdrv_drain_all()
> tests/test-bdrv-drain: bdrv_drain_all() works in coroutines now
> block: Avoid unnecessary aio_poll() in AIO_WAIT_WHILE()
> block: Really pause block jobs on drain
> block: Remove bdrv_drain_recurse()
> block: Drain recursively with a single BDRV_POLL_WHILE()
> test-bdrv-drain: Test node deletion in subtree recursion
> block: Don't poll in parent drain callbacks
> test-bdrv-drain: Graph change through parent callback
> block: Defer .bdrv_drain_begin callback to polling phase
> test-bdrv-drain: Test that bdrv_drain_invoke() doesn't poll
> block: Allow AIO_WAIT_WHILE with NULL ctx
> block: Move bdrv_drain_all_begin() out of coroutine context
> block: ignore_bds_parents parameter for drain functions
> block: Allow graph changes in bdrv_drain_all_begin/end sections
> test-bdrv-drain: Test graph changes in drain_all section
>
> Max Reitz (1):
> test-bdrv-drain: Add test for node deletion
>
> include/block/aio-wait.h | 25 +-
> include/block/block.h | 31 +-
> include/block/block_int.h | 14 +
> include/block/blockjob_int.h | 8 +
> block.c | 52 +++-
> block/io.c | 332 ++++++++++++--------
> block/mirror.c | 8 +
> block/vvfat.c | 1 +
> blockjob.c | 23 ++
> tests/test-bdrv-drain.c | 705
> +++++++++++++++++++++++++++++++++++++++++--
> 10 files changed, 1032 insertions(+), 167 deletions(-)
>
> --
> 2.13.6
>
- Re: [Qemu-devel] [PATCH v2 00/20] Drain fixes and cleanups, part 3,
Kevin Wolf <=