Messages in this thread | | | Date | Sat, 20 Jun 2009 12:01:22 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [GIT PULL] core kernel fixes |
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On Sat, 20 Jun 2009, Linus Torvalds wrote: > > On x86, the natural way to do what you want done is ONE SINGLE > INSTRUCTION! As far as I can tell, the above crazy function is 100% > equivalent to this: > > asm __inline__("lock ; addl $0,%0":"+m" (*uaddr): :"memory", "cc"); > > which really makes me think that using "get_user_pages_fast()" for it is > some truly crazy crap.
We could also take the opposite approach - knowing that this is called only when the page doesn't exist, and just doing
down_read(mmap_sem) vma = find_vma(..) ret = VM_FAULT_ERROR; if (vma && vma->vm_start <= address) ret = handle_mm_fault(mm, vma, address, 1); up_read(mmap_sem); return (ret & VM_FAULT_ERROR) ? -EFAULT : 0;
or something like that. Again, that looks saner than using get_user_pages() for this and then dropping the page.
Linus
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