On 10/09/2018 06:48 PM, Will Deacon wrote:
On Tue, Oct 09, 2018 at 04:04:21PM +0300, Kirill A. Shutemov wrote:yeah this works but some how does not seem like the right thing to do
On Tue, Oct 09, 2018 at 09:28:58AM +0530, Anshuman Khandual wrote:
A normal mapped THP page at PMD level should be correctly differentiated
from a PMD migration entry while walking the page table. A mapped THP would
additionally check positive for pmd_present() along with pmd_trans_huge()
as compared to a PMD migration entry. This just adds a new conditional test
differentiating the two while walking the page table.
Fixes: 616b8371539a6 ("mm: thp: enable thp migration in generic path")
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
On X86, pmd_trans_huge() and is_pmd_migration_entry() are always mutually
exclusive which makes the current conditional block work for both mapped
and migration entries. This is not same with arm64 where pmd_trans_huge()
returns positive for both mapped and migration entries. Could some one
please explain why pmd_trans_huge() has to return false for migration
entries which just install swap bits and its still a PMD ?
I guess it's just a design choice. Any reason why arm64 cannot do the
Anshuman, would it work to:
#define pmd_trans_huge(pmd) (pmd_present(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
but can be the very last option.