Am 20.04.2016 um 00:59 hat Max Reitz geschrieben: > Bug report: https://bugs.launchpad.net/qemu/+bug/1570134 > > If you are doing a mirror operation (I just tested with block-commit on > the active layer, but I guess any mirroring will do) while the guest has > rather heavy I/O load (or light I/O also, you just need to be more > unlucky) will lead to the cache of mirror's bitmap iterator becoming > stale and not reflect all dirty bits which are set in the drive's dirty > bitmap. > > Generally, this isn't bad because we just restart over once we are > through, and this will refresh the iterator's cache. > > But it is bad for the code which tries to find a contiguous range of > dirty chunks. This code needs to clear the bits in the iterator, so it > invokes hbitmap_iter_next() for every contiguous dirty chunk found. But > then it has to make sure that this actually cleared that chunk's dirty > bit: And if the iterator's cache is stale, this may not be the case. > Then, we run into a failed assertion. > > But detecting this discrepancy is easy and refreshing the iterator's > cache is too; and then, the assertion holds. > > Besides this (patch 2), the code which is supposed to wait for > overlapping in-flight requests on the first chunk of a dirty range is > dead. I didn't produce any problems regarding that, but I'm sure it's > not good. Patch 1 fixes that.
Thanks, applied to the block branch. Kevin
