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
2424013a99