Am 11.06.2018 um 14:23 hat Kevin Wolf geschrieben: > 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.
Without objection, applied to the block branch. Kevin
