Re: [v3,2/3] powerpc: get hugetlbpage handling more generic

On Wed, Sep 21, 2016 at 10:11:54AM +0200, Christophe Leroy wrote:

Today there are two implementations of hugetlbpages which are managed
by exclusive #ifdefs:
* FSL_BOOKE: several directory entries points to the same single hugepage
* BOOK3S: one upper level directory entry points to a table of hugepages

In preparation of implementation of hugepage support on the 8xx, we
need a mix of the two above solutions, because the 8xx needs both cases
depending on the size of pages:
* In 4k page size mode, each PGD entry covers a 4M bytes area. It means
that 2 PGD entries will be necessary to cover an 8M hugepage while a
single PGD entry will cover 8x 512k hugepages.
* In 16 page size mode, each PGD entry covers a 64M bytes area. It means
that 8x 8M hugepages will be covered by one PGD entry and 64x 512k
hugepages will be covers by one PGD entry.

This patch:
* removes #ifdefs in favor of if/else based on the range sizes
* merges the two huge_pte_alloc() functions as they are pretty similar
* merges the two hugetlbpage_init() functions as they are pretty similar

Signed-off-by: Christophe Leroy <redacted>
Reviewed-by: Aneesh Kumar K.V <redacted>

With this patch on e6500, running the hugetlb testsuite results in the
system hanging in a storm of OOM killer invocations (I'll try to debug
more deeply later).  This patch also changes the default hugepage size on
FSL book3e from 4M to 16M.

-Scott