FT> I'm not sure how this works. Have you explained the details of FT> this feature in the earlier thread? For example, in our CoW case: A write is made to a previously unremapped block. We queue that block and let userspace make a mapping. Then, we allow the write to happen, but intercept the completion (endio) and notify userspace that it has completed. Then, userspace flushes its metadata to disk and notifies the kernel to allow the endio to complete. Without this, a crash could result in an inconsistent CoW device. (Note this only needs to happen on the _initial_ write to a block) FT> I see. I don't think that you need to implement it now (simple FT> code is always better for mainline inclusion), however, it would FT> be nice to have dmu_event structure for this. Well, it's crucial for our CoW work, so unless Alasdair would prefer me to leave it out in the initial upstream push, I would like to include it. It was already implemented and working in my original version. -- Dan Smith IBM Linux Technology Center Open Hypervisor Team email: danms@xxxxxxxxxx
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