Revert "oom: remove oom_disable_count"

This reverts commit 1c294847e847c7fff33a92e2acc67dbaa87cbf43.
Revert "oom: avoid killing kthreads if they assume the oom killed thread's mm"

This reverts commit d48194fde6425ff35e6881b46449d7a924ca1969.
Revert "oom: thaw threads if oom killed thread is frozen before deferring"

This reverts commit b8b13402e88718b5df559eb26ad971fea4c00fd6.
Revert "blkpm: avoid sleep when holding queue lock"

This reverts commit 82b199a805ce50395c3ffbcd5f1a41ad699563eb.