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Subject[RFC PATCH 22/31] mm: thp: 1GB THP follow_p*d_page() support.
Date
From: Zi Yan <ziy@nvidia.com>

Add follow_page support for 1GB THPs.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
include/linux/huge_mm.h | 11 +++++++
mm/gup.c | 60 ++++++++++++++++++++++++++++++++-
mm/huge_memory.c | 73 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index bd5cc5e65de8..b1acada9ce8c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -20,6 +20,10 @@ extern int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
extern void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud);
extern int do_huge_pud_anonymous_page(struct vm_fault *vmf);
extern int do_huge_pud_wp_page(struct vm_fault *vmf, pud_t orig_pud);
+extern struct page *follow_trans_huge_pud(struct vm_area_struct *vma,
+ unsigned long addr,
+ pud_t *pud,
+ unsigned int flags);
#else
static inline void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
{
@@ -32,6 +36,13 @@ extern int do_huge_pud_wp_page(struct vm_fault *vmf, pud_t orig_pud)
{
return VM_FAULT_FALLBACK;
}
+struct page *follow_trans_huge_pud(struct vm_area_struct *vma,
+ unsigned long addr,
+ pud_t *pud,
+ unsigned int flags)
+{
+ return NULL;
+}
#endif

extern vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd);
diff --git a/mm/gup.c b/mm/gup.c
index 05acd7e2eb22..0ad0509b03fc 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -348,10 +348,68 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
if (page)
return page;
}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+ if (likely(!pud_trans_huge(*pud))) {
+ if (unlikely(pud_bad(*pud)))
+ return no_page_table(vma, flags);
+ return follow_pmd_mask(vma, address, pud, flags, ctx);
+ }
+
+ ptl = pud_lock(mm, pud);
+
+ if (unlikely(!pud_trans_huge(*pud))) {
+ spin_unlock(ptl);
+ if (unlikely(pud_bad(*pud)))
+ return no_page_table(vma, flags);
+ return follow_pmd_mask(vma, address, pud, flags, ctx);
+ }
+
+ if (flags & FOLL_SPLIT) {
+ int ret;
+ pmd_t *pmd = NULL;
+
+ page = pud_page(*pud);
+ if (is_huge_zero_page(page)) {
+
+ spin_unlock(ptl);
+ ret = 0;
+ split_huge_pud(vma, pud, address);
+ pmd = pmd_offset(pud, address);
+ split_huge_pmd(vma, pmd, address);
+ if (pmd_trans_unstable(pmd))
+ ret = -EBUSY;
+ } else {
+ get_page(page);
+ spin_unlock(ptl);
+ lock_page(page);
+ ret = split_huge_pud_page(page);
+ if (!ret)
+ ret = split_huge_page(page);
+ else {
+ unlock_page(page);
+ put_page(page);
+ goto out;
+ }
+ unlock_page(page);
+ put_page(page);
+ if (pud_none(*pud))
+ return no_page_table(vma, flags);
+ pmd = pmd_offset(pud, address);
+ }
+out:
+ return ret ? ERR_PTR(ret) :
+ follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
+ }
+ page = follow_trans_huge_pud(vma, address, pud, flags);
+ spin_unlock(ptl);
+ ctx->page_mask = HPAGE_PUD_NR - 1;
+ return page;
+#else
if (unlikely(pud_bad(*pud)))
return no_page_table(vma, flags);
-
return follow_pmd_mask(vma, address, pud, flags, ctx);
+#endif
}

static struct page *follow_p4d_mask(struct vm_area_struct *vma,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 41adc103ead1..191261771452 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1309,6 +1309,77 @@ struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
return page;
}

+/*
+ * FOLL_FORCE can write to even unwritable pmd's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pud(pud_t pud, unsigned int flags)
+{
+ return pud_write(pud) ||
+ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pud_dirty(pud));
+}
+
+struct page *follow_trans_huge_pud(struct vm_area_struct *vma,
+ unsigned long addr,
+ pud_t *pud,
+ unsigned int flags)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page *page = NULL;
+
+ assert_spin_locked(pud_lockptr(mm, pud));
+
+ if (flags & FOLL_WRITE && !can_follow_write_pud(*pud, flags))
+ goto out;
+
+ /* Avoid dumping huge zero page */
+ if ((flags & FOLL_DUMP) && is_huge_zero_pud(*pud))
+ return ERR_PTR(-EFAULT);
+
+ /* Full NUMA hinting faults to serialise migration in fault paths */
+ /*&& pud_protnone(*pmd)*/
+ if ((flags & FOLL_NUMA))
+ goto out;
+
+ page = pud_page(*pud);
+ VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
+ if (flags & FOLL_TOUCH)
+ touch_pud(vma, addr, pud, flags);
+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
+ /*
+ * We don't mlock() pte-mapped THPs. This way we can avoid
+ * leaking mlocked pages into non-VM_LOCKED VMAs.
+ *
+ * For anon THP:
+ *
+ * We do the same thing as PMD-level THP.
+ *
+ * For file THP:
+ *
+ * No support yet.
+ *
+ */
+
+ if (PageAnon(page) && compound_mapcount(page) != 1)
+ goto skip_mlock;
+ if (PagePUDDoubleMap(page) || !page->mapping)
+ goto skip_mlock;
+ if (!trylock_page(page))
+ goto skip_mlock;
+ lru_add_drain();
+ if (page->mapping && !PagePUDDoubleMap(page))
+ mlock_vma_page(page);
+ unlock_page(page);
+ }
+skip_mlock:
+ page += (addr & ~HPAGE_PUD_MASK) >> PAGE_SHIFT;
+ VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
+ if (flags & FOLL_GET)
+ get_page(page);
+
+out:
+ return page;
+}
int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
struct vm_area_struct *vma)
@@ -1991,7 +2062,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
goto out;

page = pmd_page(*pmd);
- VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
+ VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page) && !PMDPageInPUD(page), page);
if (flags & FOLL_TOUCH)
touch_pmd(vma, addr, pmd, flags);
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
--
2.20.1
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