This reverts commit 59eab109.

The change suppressed EFAULT originating from uiomove().  The deadlock
avoidance mechanism implemented by vn_io_fault1() in the VFS handles
such errors by wiring the user pages and retrying, but this change
caused read() to return early instead.  This can result in short I/O,
causing misbehaviour in some applications, and possibly other
consequences.

Until this is resolved somehow, revert the commit.

Approved by:	mm