Hi Anshuman,
Thank you very much for looking at this. My reply below::
On 10/06/2017 02:48 AM, Anshuman Khandual wrote:
On 10/04/2017 08:59 PM, Pavel Tatashin wrote:
This patch fixes another existing issue on systems that have holes in
zones i.e CONFIG_HOLES_IN_ZONE is defined.
In for_each_mem_pfn_range() we have code like this:
if (!pfn_valid_within(pfn)
goto free_range;
Note: 'page' is not set to NULL and is not incremented but 'pfn' advances.
page is initialized to NULL at the beginning of the function.
Yes, it is initialized to NULL but at the beginning of
for_each_mem_pfn_range() loop
PFN advances but we dont proceed unless pfn_valid_within(pfn)
holds true which basically should have checked with arch call
back if the PFN is valid in presence of memory holes as well.
Is not this correct ?
Correct, if pfn_valid_within() is false we jump to the "goto
free_range;", which is at the end of for (; pfn < end_pfn; pfn++) loop,
so we are not jumping outside of this loop.
Thus means if deferred struct pages are enabled on systems with these kind
of holes, linux would get memory corruptions. I have fixed this issue by
defining a new macro that performs all the necessary operations when we
free the current set of pages.
If we bail out in case PFN is not valid, then how corruption
can happen ?
We are not bailing out. We continue next iteration with next pfn, but
page is not incremented.
Please let me know if I am missing something.
Thank you,
Pasha
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