When we have a page fault for the address which is backed by a hugepage
under migration, the kernel can't wait correctly until the migration
finishes. This is because pte_offset_map_lock() can't get a correct
migration entry for hugepage. This patch adds migration_entry_wait_huge()
to separate code path between normal pages and hugepages.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 2 ++
include/linux/swapops.h | 4 ++++
mm/hugetlb.c | 4 ++--
mm/migrate.c | 24 ++++++++++++++++++++++++
4 files changed, 32 insertions(+), 2 deletions(-)
diff --git v3.8.orig/include/linux/hugetlb.h v3.8/include/linux/hugetlb.h
index 0c80d3f..40b27f6 100644
--- v3.8.orig/include/linux/hugetlb.h
+++ v3.8/include/linux/hugetlb.h
@@ -43,6 +43,7 @@ int hugetlb_mempolicy_sysctl_handler(struct ctl_table *, int,
#endif
int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
+int is_hugetlb_entry_migration(pte_t pte);
int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
struct page **, struct vm_area_struct **,
unsigned long *, int *, int, unsigned int flags);
@@ -109,6 +110,7 @@ static inline unsigned long hugetlb_total_pages(void)
#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; })
#define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL)
#define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; })
+#define is_hugetlb_entry_migration(pte) ({ BUG(); 0; })
#define hugetlb_prefault(mapping, vma) ({ BUG(); 0; })
static inline void hugetlb_report_meminfo(struct seq_file *m)
{
diff --git v3.8.orig/include/linux/swapops.h v3.8/include/linux/swapops.h
index 47ead51..f68efdd 100644
--- v3.8.orig/include/linux/swapops.h
+++ v3.8/include/linux/swapops.h
@@ -137,6 +137,8 @@ static inline void make_migration_entry_read(swp_entry_t *entry)
extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address);
+extern void migration_entry_wait_huge(struct mm_struct *mm, pmd_t *pmd,
+ unsigned long address);
#else
#define make_migration_entry(page, write) swp_entry(0, 0)
@@ -148,6 +150,8 @@ static inline int is_migration_entry(swp_entry_t swp)
static inline void make_migration_entry_read(swp_entry_t *entryp) { }
static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address) { }
+static inline void migration_entry_wait_huge(struct mm_struct *mm, pmd_t *pmd,
+ unsigned long address) { }
static inline int is_write_migration_entry(swp_entry_t entry)
{
return 0;
diff --git v3.8.orig/mm/hugetlb.c v3.8/mm/hugetlb.c
index 546db81..351025e 100644
--- v3.8.orig/mm/hugetlb.c
+++ v3.8/mm/hugetlb.c
@@ -2313,7 +2313,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
return -ENOMEM;
}
-static int is_hugetlb_entry_migration(pte_t pte)
+int is_hugetlb_entry_migration(pte_t pte)
{
swp_entry_t swp;
@@ -2823,7 +2823,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (ptep) {
entry = huge_ptep_get(ptep);
if (unlikely(is_hugetlb_entry_migration(entry))) {
- migration_entry_wait(mm, (pmd_t *)ptep, address);
+ migration_entry_wait_huge(mm, (pmd_t *)ptep, address);
return 0;
} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
return VM_FAULT_HWPOISON_LARGE |
diff --git v3.8.orig/mm/migrate.c v3.8/mm/migrate.c
index 2fd8b4a..7d84f4c 100644
--- v3.8.orig/mm/migrate.c
+++ v3.8/mm/migrate.c
@@ -236,6 +236,30 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
pte_unmap_unlock(ptep, ptl);
}
+void migration_entry_wait_huge(struct mm_struct *mm, pmd_t *pmd,
+ unsigned long address)
+{
+ spinlock_t *ptl = pte_lockptr(mm, pmd);
+ pte_t pte;
+ swp_entry_t entry;
+ struct page *page;
+
+ spin_lock(ptl);
+ pte = huge_ptep_get((pte_t *)pmd);
+ if (!is_hugetlb_entry_migration(pte))
+ goto out;
+ entry = pte_to_swp_entry(pte);
+ page = migration_entry_to_page(entry);
+ if (!get_page_unless_zero(page))
+ goto out;
+ spin_unlock(ptl);
+ wait_on_page_locked(page);
+ put_page(page);
+ return;
+out:
+ spin_unlock(ptl);
+}
+
#ifdef CONFIG_BLOCK
/* Returns true if all buffers are successfully locked */
static bool buffer_migrate_lock_buffers(struct buffer_head *head,
--
1.7.11.7
--
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