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Subject[patch 2/6] memory hotplug for hugetlbpages
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This is a part 2 of memory hotplug patches for hugetlbpages.

$Id: va-hugepagefault.patch,v 1.8 2004/04/05 06:13:36 taka Exp $

--- linux-2.6.5.ORG/include/linux/hugetlb.h Mon Apr 5 16:13:27 2032
+++ linux-2.6.5/include/linux/hugetlb.h Mon Apr 5 16:15:15 2032
@@ -24,10 +24,12 @@ struct page *follow_huge_addr(struct mm_
unsigned long address, int write);
struct vm_area_struct *hugepage_vma(struct mm_struct *mm,
unsigned long address);
-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write);
+struct page *follow_huge_pmd(struct mm_struct *mm, struct vm_area_struct *,
+ unsigned long address, pmd_t *pmd, int write);
int is_aligned_hugepage_range(unsigned long addr, unsigned long len);
int pmd_huge(pmd_t pmd);
+extern int hugetlb_fault(struct mm_struct *, struct vm_area_struct *,
+ int, unsigned long);

extern int htlbpage_max;

@@ -72,12 +74,13 @@ static inline unsigned long hugetlb_tota
#define hugetlb_report_meminfo(buf) 0
#define hugepage_vma(mm, addr) 0
#define mark_mm_hugetlb(mm, vma) do { } while (0)
-#define follow_huge_pmd(mm, addr, pmd, write) 0
+#define follow_huge_pmd(mm, vma, addr, pmd, write) 0
#define is_aligned_hugepage_range(addr, len) 0
#define prepare_hugepage_range(addr, len) (-EINVAL)
#define pmd_huge(x) 0
#define is_hugepage_only_range(addr, len) 0
#define hugetlb_free_pgtables(tlb, prev, start, end) do { } while (0)
+#define hugetlb_fault(mm, vma, write, addr) 0

#ifndef HPAGE_MASK
#define HPAGE_MASK 0 /* Keep the compiler happy */
--- linux-2.6.5.ORG/mm/memory.c Mon Apr 5 16:13:38 2032
+++ linux-2.6.5/mm/memory.c Mon Apr 5 16:14:02 2032
@@ -643,7 +643,7 @@ follow_page(struct mm_struct *mm, unsign
if (pmd_none(*pmd))
goto out;
if (pmd_huge(*pmd))
- return follow_huge_pmd(mm, address, pmd, write);
+ return follow_huge_pmd(mm, vma, address, pmd, write);
if (pmd_bad(*pmd))
goto out;

@@ -1628,7 +1628,7 @@ int handle_mm_fault(struct mm_struct *mm
inc_page_state(pgfault);

if (is_vm_hugetlb_page(vma))
- return VM_FAULT_SIGBUS; /* mapping truncation does this. */
+ return hugetlb_fault(mm, vma, write_access, address);

/*
* We need the page table lock to synchronize with kswapd
--- linux-2.6.5.ORG/arch/i386/mm/hugetlbpage.c Mon Apr 5 16:13:30 2032
+++ linux-2.6.5/arch/i386/mm/hugetlbpage.c Mon Apr 5 16:14:02 2032
@@ -142,8 +142,10 @@ int copy_hugetlb_page_range(struct mm_st
goto nomem;
src_pte = huge_pte_offset(src, addr);
entry = *src_pte;
- ptepage = pte_page(entry);
- get_page(ptepage);
+ if (!pte_none(entry)) {
+ ptepage = pte_page(entry);
+ get_page(ptepage);
+ }
set_pte(dst_pte, entry);
dst->rss += (HPAGE_SIZE / PAGE_SIZE);
addr += HPAGE_SIZE;
@@ -173,6 +175,11 @@ follow_hugetlb_page(struct mm_struct *mm

pte = huge_pte_offset(mm, vaddr);

+ if (!pte || pte_none(*pte)) {
+ hugetlb_fault(mm, vma, 0, vaddr);
+ pte = huge_pte_offset(mm, vaddr);
+ }
+
/* hugetlb should be locked, and hence, prefaulted */
WARN_ON(!pte || pte_none(*pte));

@@ -261,12 +268,17 @@ int pmd_huge(pmd_t pmd)
}

struct page *
-follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
+follow_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, int write)
{
struct page *page;

page = pte_page(*(pte_t *)pmd);
+
+ if (!page) {
+ hugetlb_fault(mm, vma, write, address);
+ page = pte_page(*(pte_t *)pmd);
+ }
if (page) {
page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
get_page(page);
@@ -329,54 +341,94 @@ zap_hugepage_range(struct vm_area_struct
spin_unlock(&mm->page_table_lock);
}

-int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
+int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, int write_access, unsigned long address)
{
- struct mm_struct *mm = current->mm;
- unsigned long addr;
- int ret = 0;
+ struct file *file = vma->vm_file;
+ struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
+ struct page *page;
+ unsigned long idx;
+ pte_t *pte = huge_pte_alloc(mm, address);
+ int ret;

BUG_ON(vma->vm_start & ~HPAGE_MASK);
BUG_ON(vma->vm_end & ~HPAGE_MASK);

- spin_lock(&mm->page_table_lock);
- for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
- unsigned long idx;
- pte_t *pte = huge_pte_alloc(mm, addr);
- struct page *page;
+ if (!pte) {
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }

- if (!pte) {
- ret = -ENOMEM;
+ if (!pte_none(*pte)) {
+ ret = VM_FAULT_MINOR;
+ goto out;
+ }
+
+ idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
+ + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+again:
+ page = find_lock_page(mapping, idx);
+
+ if (!page) {
+ if (hugetlb_get_quota(mapping)) {
+ ret = VM_FAULT_SIGBUS;
goto out;
}
- if (!pte_none(*pte))
- continue;
-
- idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
- + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
- page = find_get_page(mapping, idx);
+ page = alloc_hugetlb_page();
if (!page) {
- /* charge the fs quota first */
- if (hugetlb_get_quota(mapping)) {
- ret = -ENOMEM;
- goto out;
- }
- page = alloc_hugetlb_page();
- if (!page) {
- hugetlb_put_quota(mapping);
- ret = -ENOMEM;
- goto out;
- }
- ret = add_to_page_cache(page, mapping, idx, GFP_ATOMIC);
+ hugetlb_put_quota(mapping);
+ ret = VM_FAULT_SIGBUS;
+ goto out;
+ }
+ ret = add_to_page_cache(page, mapping, idx, GFP_ATOMIC);
+ if (ret) {
+ hugetlb_put_quota(mapping);
+ free_huge_page(page);
unlock_page(page);
- if (ret) {
- hugetlb_put_quota(mapping);
- free_huge_page(page);
- goto out;
- }
+ goto again;
}
+ }
+ spin_lock(&mm->page_table_lock);
+ if (pte_none(*pte)) {
set_huge_pte(mm, vma, page, pte, vma->vm_flags & VM_WRITE);
+ flush_tlb_page(vma, address);
+ update_mmu_cache(vma, address, *pte);
+ } else {
+ huge_page_release(page);
}
+ spin_unlock(&mm->page_table_lock);
+ unlock_page(page);
+ ret = VM_FAULT_MINOR;
out:
+ return ret;
+}
+
+int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
+{
+ struct mm_struct *mm = current->mm;
+ unsigned long addr;
+ int ret = 0;
+
+ BUG_ON(vma->vm_start & ~HPAGE_MASK);
+ BUG_ON(vma->vm_end & ~HPAGE_MASK);
+
+ spin_lock(&mm->page_table_lock);
+ for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
+ if (addr < vma->vm_start)
+ addr = vma->vm_start;
+ if (addr >= vma->vm_end) {
+ ret = 0;
+ break;
+ }
+ spin_unlock(&mm->page_table_lock);
+ ret = hugetlb_fault(mm, vma, 1, addr);
+ schedule();
+ spin_lock(&mm->page_table_lock);
+ if (ret == VM_FAULT_SIGBUS) {
+ ret = -ENOMEM;
+ break;
+ }
+ ret = 0;
+ }
spin_unlock(&mm->page_table_lock);
return ret;
}
-
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