FOLL_SPLIT is used only in two places: migration and s390.
Let's replace it with explicit split and remove FOLL_SPLIT.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
Documentation/vm/transhuge.txt | 11 -----------
arch/s390/mm/pgtable.c | 17 +++++++++++------
include/linux/mm.h | 1 -
mm/gup.c | 4 ----
mm/migrate.c | 7 ++++++-
5 files changed, 17 insertions(+), 23 deletions(-)
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index 6b31cfbe2a9a..df1794a9071f 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -263,17 +263,6 @@ same constrains that applies to hugetlbfs too, so any driver capable
of handling GUP on hugetlbfs will also work fine on transparent
hugepage backed mappings.
-In case you can't handle compound pages if they're returned by
-follow_page, the FOLL_SPLIT bit can be specified as parameter to
-follow_page, so that it will split the hugepages before returning
-them. Migration for example passes FOLL_SPLIT as parameter to
-follow_page because it's not hugepage aware and in fact it can't work
-at all on hugetlbfs (but it instead works fine on transparent
-hugepages thanks to FOLL_SPLIT). migration simply can't deal with
-hugepages being returned (as it's not only checking the pfn of the
-page and pinning it during the copy but it pretends to migrate the
-memory in regular page sizes and with regular pte/pmd mappings).
-
== Optimizing the applications ==
To be guaranteed that the kernel will map a 2M page immediately in any
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 19daa53a3da4..a43f4d33f376 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -1248,20 +1248,25 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline void thp_split_vma(struct vm_area_struct *vma)
+static int thp_split_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
{
- unsigned long addr;
-
- for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE)
- follow_page(vma, addr, FOLL_SPLIT);
+ struct vm_area_struct *vma = walk->vma;
+ split_huge_page_pmd(vma, addr, pmd);
+ return 0;
}
static inline void thp_split_mm(struct mm_struct *mm)
{
struct vm_area_struct *vma;
+ struct mm_walk thp_split_walk = {
+ .mm = mm,
+ .pmd_entry = thp_split_pmd,
+
+ };
for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
- thp_split_vma(vma);
+ walk_page_vma(vma, &thp_split_walk);
vma->vm_flags &= ~VM_HUGEPAGE;
vma->vm_flags |= VM_NOHUGEPAGE;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c9f866760df8..98c11c5be0ad 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1985,7 +1985,6 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
* and return without waiting upon it */
#define FOLL_MLOCK 0x40 /* mark page as mlocked */
-#define FOLL_SPLIT 0x80 /* don't return transhuge pages, split them */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
diff --git a/mm/gup.c b/mm/gup.c
index 91d044b1600d..03f34c417591 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -192,10 +192,6 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
return no_page_table(vma, flags);
if (pmd_trans_huge(*pmd)) {
- if (flags & FOLL_SPLIT) {
- split_huge_page_pmd(vma, address, pmd);
- return follow_page_pte(vma, address, pmd, flags);
- }
ptl = pmd_lock(mm, pmd);
if (likely(pmd_trans_huge(*pmd))) {
if (unlikely(pmd_trans_splitting(*pmd))) {
diff --git a/mm/migrate.c b/mm/migrate.c
index f78ec9bd454d..ad4694515f31 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1236,7 +1236,7 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
goto set_status;
- page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
+ page = follow_page(vma, pp->addr, FOLL_GET);
err = PTR_ERR(page);
if (IS_ERR(page))
@@ -1246,6 +1246,11 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
if (!page)
goto set_status;
+ if (PageTransHuge(page) && split_huge_page(page)) {
+ err = -EBUSY;
+ goto set_status;
+ }
+
/* Use PageReserved to check for zero page */
if (PageReserved(page))
goto put_and_set;
--
2.1.1
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