When moving swap file locations, old swap file is left on each device

[kallisti5]

When you move swap locations, an old swap file is left on the previous device. This file can be erased by hand post-reboot, however it should be cleaned up automatically.

Process:

• Swap file location changed by user
• Swap file is in use by os... so it can't be erased
• After reboot, kernel uses new swap file specified.
• Old swap file still exists.

This is generally a problem of knowing where the old swap file *was* on reboot. a syscall may be a good solution (not requiring a reboot for swapfile changes, maybe a _kern_swap_reprovision call that will:

• Make the kernel flush the swap file into memory (if possible or return a failure)
• Make the kernel erase the current swap file from disk, and re-read the virtual_memory config to set up the new swap file.