[PATCH 0/4] fix AIL pushing under heavy concurrent metadata loads

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

This series fixes hangs under heavy concurrent metadata workloads.  The
underlying issues seem fairly old but only really started to show when
enabling delaylog and the workqueue based AIL pushed.

A big thanks to Stefan Priebe for reporting the problem, providing a
reproducer and test filesystem image as well as testing the patches
on his system.