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Subject[PATCHv10 33/36] migrate_pages: try to split pages on qeueuing
Date
We are not able to migrate THPs. It means it's not enough to split only
PMD on migration -- we need to split compound page under it too.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
---
mm/mempolicy.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 8102f30a3895..8f128379172e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -489,14 +489,31 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
struct page *page;
struct queue_pages *qp = walk->private;
unsigned long flags = qp->flags;
- int nid;
+ int nid, ret;
pte_t *pte;
spinlock_t *ptl;

- split_huge_pmd(vma, pmd, addr);
- if (pmd_trans_unstable(pmd))
- return 0;
+ if (pmd_trans_huge(*pmd)) {
+ ptl = pmd_lock(walk->mm, pmd);
+ if (pmd_trans_huge(*pmd)) {
+ page = pmd_page(*pmd);
+ if (is_huge_zero_page(page)) {
+ spin_unlock(ptl);
+ split_huge_pmd(vma, pmd, addr);
+ } else {
+ get_page(page);
+ spin_unlock(ptl);
+ lock_page(page);
+ ret = split_huge_page(page);
+ unlock_page(page);
+ put_page(page);
+ if (ret)
+ return 0;
+ }
+ }
+ }

+retry:
pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE) {
if (!pte_present(*pte))
@@ -513,6 +530,18 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
nid = page_to_nid(page);
if (node_isset(nid, *qp->nmask) == !!(flags & MPOL_MF_INVERT))
continue;
+ if (PageTail(page) && PageAnon(page)) {
+ get_page(page);
+ pte_unmap_unlock(pte - 1, ptl);
+ lock_page(page);
+ ret = split_huge_page(page);
+ unlock_page(page);
+ put_page(page);
+ /* Failed to split -- skip. */
+ if (ret)
+ continue;
+ goto retry;
+ }

if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
migrate_page_add(page, qp->pagelist, flags);
--
2.5.0


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