K 10
svn:author
V 8
bmilekic
K 8
svn:date
V 27
2000-11-11T23:12:27.000000Z
K 7
svn:log
V 600
Add new M_RDONLY flag, which can be set during setup (MEXTADD, for example),
and which indicates that the ext_buf is to be marked READ-ONLY.

Also introduce M_WRITABLE() macro, which will return true if:
* M_RDONLY is _not_ set AND:
* either mbuf has no ext_buf attached OR it has an ext_buf attached but the ref
  count is NOT above 1.

sf_bufs (sendfile) are marked M_RDONLY.

Now code determining whether an mbuf's data area is "shared" or not can be
made to use this instead of doing its own (often incorrect) thing.

Submitted by: bmilekic, dwmalone, and Ian Dowse
Reviewed by: dwmalone, jlemon

END