On Thu, 2007-04-12 at 12:20 +1000, Benjamin Herrenschmidt wrote: > This is a "first step" as there are still cleanups to be done in various > areas touched by that code but I think it's probably good to go as is and > at least enables me to implement what I need for PowerPC. > > (Andrew, this is also candidate for 2.6.22 since I haven't had any real > objection, mostly suggestion for improving further, which I'll try to > do later, and I have further powerpc patches that rely on this). > > The current get_unmapped_area code calls the f_ops->get_unmapped_area or > the arch one (via the mm) only when MAP_FIXED is not passed. That makes > it impossible for archs to impose proper constraints on regions of the > virtual address space. To work around that, get_unmapped_area() then > calls some hugetlbfs specific hacks. > > This cause several problems, among others: > > - It makes it impossible for a driver or filesystem to do the same thing > that hugetlbfs does (for example, to allow a driver to use larger page > sizes to map external hardware) if that requires applying a constraint > on the addresses (constraining that mapping in certain regions and other > mappings out of those regions). > > - Some archs like arm, mips, sparc, sparc64, sh and sh64 already want > MAP_FIXED to be passed down in order to deal with aliasing issues. > The code is there to handle it... but is never called. >
Is there any support consideration for nommu arch such as blackfin which is in the -mm tree now? It is very kind of you to point out some idea about MAP_FIXED for Blackfin arch, I will do some help for this. Thanks -Bryan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
