Re: Why still no mmap ( MAP_ANON | MAP_SHARED ) allowed 2.2.14+?

[Chris Wedgwood]

    Could somebody tell me what the status is on getting mmap to work
    with both MAP_ANON and MAP_SHARED at the same time? This doesn't seem
    to work even on my recent 2.2-14 kernel (and a reading of mmap.c
    confirmed this). Every other major UNIX supports this, why not our
    beloved Tux? 

Because 2.2.x kernels require a backing-store for such mappings, for
shared-anonymous there is none.

This shortcoming appears to have be corrected for the upcoming 2.4.x
kernels, perhaps you could use them?

    It seems to me that this is THE way to have a parent share large
    amounts of data with several children that just need to
    read/search through it.

As a workaround, create a file and unlink it immediately, then
ftruncate and mmap it.

  --cw