Re: PATCH [2.4.0test10]: Kiobuf#02, fault-in fix

Jeff Garzik
2000-11-02T14:30:10Z

"Stephen C. Tweedie" wrote:
> Next part of the kiobuf diffs: fix the fact that handle_mm_fault
> doesn't guarantee to complete the operation in all cases; doesn't
> guarantee that the resulting pte is writable if write access was
> requested; and doesn't pin the page against immediately being swapped
> back out.

Dumb question time, if you don't mind. :) All code examples are from
mm/memory.c.

This seems to imply datain means 'read access':
int datain = (rw == READ);

This seems to further imply datain means 'read access':
if (((datain) && (!(vma->vm_flags & VM_WRITE))) ||

And then we pass 'datain' as the 'write_access' arg of handle_mm_fault:
if (handle_mm_fault(current->mm, vma, ptr, datain) <= 0)

Further down in make_pages_present, there seems to be the opposite:
write = (vma->vm_flags & VM_WRITE) != 0;
[...]
if (handle_mm_fault(mm, vma, addr, write) < 0)

So, why do we pass 'datain' as the 'write_access' arg of
handle_mm_fault?
(and now in your 02-faultfix.diff patch, as the 'write' arg of
follow_page)

Regards,

Jeff

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Jeff Garzik | Dinner is ready when
Building 1024 | the smoke alarm goes off.
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