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larger than the operational region. If the op region size is zero, clipping would create a zero-sized map entry. The result is that vm map splay starts behaving inconsistently, sometimes returning zero-sized entry, sometimes the next (or previous) entry. One step further, it could result in e.g. vm_map_wire() setting MAP_ENTRY_IN_TRANSITION on the zero-sized entry, but failing to clear it in the done part. The vm_map_delete() than hangs forever waiting for the flag removal. Verify for zero-length requests and act as if it is always successfull without performing any action on the address space. Diagnosed by: pho Tested by: pho (previous version) Reviewed by: alc (previous version) Sponsored by: The FreeBSD Foundation MFC after: 1 week