Hello.

It seems right now there is no way to
expand the anonymous shared mappings
(or am I missing something?)
This makes this mechanism practically
useless for many tasks, it otherwise could
suit very well, I beleive.
The attached patch implements a simple
nopage vm op for anonymous shared mappings,
which allows to expand them with mremap().
Attached is also a test-case which crashes
with bus error without the patch and works
properly with the patch (it tries to expand
the mapping, but without the patch it is
not possible).
The patch is against 2.6.7-rc3-mm2, but
should work with any 2.6.6 I beleive.

I would be glad to hear any comments on that.
I really would like to use the anonymous shared
mappings rather than those heavy-weight
alternatives like shm_open() and such, when
appropriate, but without the mremap() support,
this looks quite impossible to me.