Trance

Elves don't need to sleep. Instead, they meditate deeply, remaining semiconscious, for 4 hours a day. While meditating, you can dream after a fashion; such dreams are actually mental exercises that have become reflexive through years of practice. After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.

You don't need to sleep, and magic can't put you to sleep. You can finish a Long Rest in 4 hours if you spend those hours in a trancelike meditation, during which you remain semiconscious.