Messages in this thread | | | Date | Mon, 1 Aug 2005 15:01:24 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [patch 2.6.13-rc4] fix get_user_pages bug |
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On Mon, 1 Aug 2005, Linus Torvalds wrote: > > Of course, if VM_MAYWRITE is not set, you could just convert it silently > to a MAP_PRIVATE at the VM level (that's literally what we used to do, > back when we didn't support writable shared mappings at all, all those > years ago), so at least now the COW behaviour would match the vma_flags.
Heh. I just checked. We still do exactly that:
if (!(file->f_mode & FMODE_WRITE)) vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
some code never dies ;)
However, we still set the VM_MAYSHARE bit, and thats' the one that mm/rmap.c checks for some reason. I don't see quite why - VM_MAYSHARE doesn't actually ever do anything else than make sure that we try to allocate a mremap() mapping in a cache-coherent space, I think (ie it's a total no-op on any sane architecture, and as far as rmap is concerned on all of them).
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