4d6a407bdd
context. This fixes a long-standing but seldomly seen deadlock, where the kernel was holding pages busy (due to e.g. readahead request) while waiting for the server to respond, and the server made a callback into the kernel asking to invalidate those pages. ... or, well, theoretically fixes, since I didn't have any reliable way of repeating the deadlock and I think I saw it only twice.