VFS_LOCK_GIANT will conditionally acquire the Giant lock if the file system referenced by mp is marked as MPSAFE or not, returning a flag indicating whether Giant was set, which may later be passed to VFS_UNLOCK_GIANT. The value of mp will typically be derived from the mount pointer in a vnode on which a VFS operation will be performed.
VFS_UNLOCK_GIANT conditionally releases the Giant lock if the passed vfslocked argument is non-zero. It is expected that the argument will be derived from the return values of
.Vn VFS_LOCK_GIANT or NDHASGIANT(9).
VFS_LOCK_GIANT returns a boolean indicating whether or not Giant was acquired.
mutex(9), NDHASGIANT(9), vnode(9)