Re: [Bug 207861] New: mremap MAP_ANONYMOUS|MAP_SHARED grow provide bad mapping.

[Phi Debian <phi.debian@gmail.com>]

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Hi All,

Following up, I think I got the big picture with what you said, and then I
think, that 'may be' there is no real use case for
MAP__ANONYMOUS|MAP_SHARED, well I guess we can even say there is none
otherwise they would have voiced long ago :) I got trapped into it in a
multithreaded app trying to be smart and grow the regions that way :). I
guess this could be closed with a simple little notice in the man page,
eventually in the BUGS section, specifying that using mremap() on
MAP_SHARED is not supported beside the virtual addr aliasing already
mentioned. I got trapped after rereading again and again the fine manual,
and thinking for a minute I must miss something.

Note that MAP__ANONYMOUS|MAP_SHARED works nicely, and this one is very
useful to implement performant 'realloc' without copy for page (multipages)
realloc, with all the precaution that no addr of the memory region got to
be taken due to the vaddr migration potential, that's already mentioned in
the man page.

So the fix is simply docco I guess :)

Cheers,
Phi

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