tree 7d9b5d74f6f51255fe06649511bf39d1a0516356
parent 0ac52dd7666d5c0d0147d73a8e4b1d1ffd81cdf3
author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> 1371718823 +0530
committer Benjamin Herrenschmidt <benh@kernel.crashing.org> 1371794516 +1000

powerpc: Prevent gcc to re-read the pagetables

GCC is very likely to read the pagetables just once and cache them in
the local stack or in a register, but it is can also decide to re-read
the pagetables. The problem is that the pagetable in those places can
change from under gcc.

With THP/hugetlbfs the pmd (and pgd for hugetlbfs giga pages) can
change under gup_fast. The pages won't be freed untill we finish
gup fast because we have irq disabled and we free these pages via
rcu callback.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>