[cc to parisc list] On Thu, 2012-11-01 at 16:45 -0700, Michel Lespinasse wrote: > Hi, > > I am currently working on a patchset to avoid the brute-force search > in arch_get_unmapped_area functions (and also pushes some of it back > into generic code). So far I've only sent it as an RFC on linux-mm. Actually, I read linux-mm pretty closely (at least for the cgroups stuff), but I must have missed it. In general, if you need the attention of arch maintainers, linux-arch is the right list to cc. > Looking at the arch/parisc/kernel/sys_parisc.c implementation of > get_shared_area(), I do have a concern though. The function basically > ignores the pgoff argument, so that if one creates a shared mapping of > pages 0-N of a file, and then a separate shared mapping of pages 1-N > of that same file, both will have the same cache offset for their > starting address. > > This looks like this would create obvious aliasing issues. Am I > misreading this ? I can't understand how this could work good enough > to be undetected, so there must be something I'm missing here ??? No, I think it does. I also think the pgoff != 0 case is rare, so it doesn't show very often. To test this, I booted up with a printk for every pgoff != 0 and it didn't trigger, so it's probably not seen in the ordinary course of events. Finally, we have a test for inequvalent aliases in flush_dcache_page, so even if we do get the inequivalency, we'll resolve it correctly. James -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
