kern/vfs_bio.c 1.295 and friends)

Approved by:	Release Engineers

blocks beyond the file EOF.  Fixes bogus mmap() fault on the
last block of certain files on CDRom.

Reported by: peter / Yahoo

fragment where the dirty bits on the VM pages would never get cleared.
The bug could cause unnecessary disk writing every 30-60 seconds and
potentially force more vnodes to remain in the vnode cache, but doesn't
occur very often so most people don't need to worry.

solution.  See commitlogs/sys '2000/12/26 11:41:38 PST'

Merge the contents (less some trivial bordering the silly comments)
of <vm/vm_prot.h> and <vm/vm_inherit.h> into <vm/vm.h>.  This puts
the #defines for the vm_inherit_t and vm_prot_t types next to their
typedefs.

This paves the road for the commit to follow shortly: change
useracc() to use VM_PROT_{READ|WRITE} rather than B_{READ|WRITE}
as argument.

    underlying physical sector size when aligning I/O transfer sizes.
    It cannot assume 512 bytes.

    We assume the underlying sector size is a power of 2.  If it isn't,
    mmap() will break badly anyway (in the same way mmap broke with NFS
    when NFS tried to cache piecemeal write ranges in buffers, before
    we enforced read-buffer-before-write-piecemeal for NFS).

Reviewed by:	Alan Cox <alc@cs.rice.edu>, David Greenman <dg@root.com>

of a vm_page.

Use it.

Submitted by:	dillon