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Subject[PATCH 3/4] mm: move_page_tables{,_up}
Provide functions for moving page tables upwards.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ollie Wild <aaw@google.com>
---
include/linux/mm.h | 7 +++
mm/mremap.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 110 insertions(+), 2 deletions(-)
Index: linux-2.6-2/include/linux/mm.h
===================================================================
--- linux-2.6-2.orig/include/linux/mm.h 2007-06-01 10:50:58.000000000 +0200
+++ linux-2.6-2/include/linux/mm.h 2007-06-01 10:57:26.000000000 +0200
@@ -788,6 +787,12 @@ int FASTCALL(set_page_dirty(struct page
int set_page_dirty_lock(struct page *page);
int clear_page_dirty_for_io(struct page *page);

+extern unsigned long move_page_tables(struct vm_area_struct *vma,
+ unsigned long old_addr, struct vm_area_struct *new_vma,
+ unsigned long new_addr, unsigned long len);
+extern unsigned long move_page_tables_up(struct vm_area_struct *vma,
+ unsigned long old_addr, struct vm_area_struct *new_vma,
+ unsigned long new_addr, unsigned long len);
extern unsigned long do_mremap(unsigned long addr,
unsigned long old_len, unsigned long new_len,
unsigned long flags, unsigned long new_addr);
Index: linux-2.6-2/mm/mremap.c
===================================================================
--- linux-2.6-2.orig/mm/mremap.c 2007-06-01 10:50:58.000000000 +0200
+++ linux-2.6-2/mm/mremap.c 2007-06-01 10:57:45.000000000 +0200
@@ -118,9 +118,63 @@ static void move_ptes(struct vm_area_str
spin_unlock(&mapping->i_mmap_lock);
}

+static void move_ptes_up(struct vm_area_struct *vma, pmd_t *old_pmd,
+ unsigned long old_addr, unsigned long old_end,
+ struct vm_area_struct *new_vma, pmd_t *new_pmd,
+ unsigned long new_addr)
+{
+ struct address_space *mapping = NULL;
+ struct mm_struct *mm = vma->vm_mm;
+ pte_t *old_pte, *new_pte, pte;
+ spinlock_t *old_ptl, *new_ptl;
+ unsigned long new_end = new_addr + (old_end - old_addr);
+
+ if (vma->vm_file) {
+ /*
+ * Subtle point from Rajesh Venkatasubramanian: before
+ * moving file-based ptes, we must lock vmtruncate out,
+ * since it might clean the dst vma before the src vma,
+ * and we propagate stale pages into the dst afterward.
+ */
+ mapping = vma->vm_file->f_mapping;
+ spin_lock(&mapping->i_mmap_lock);
+ if (new_vma->vm_truncate_count &&
+ new_vma->vm_truncate_count != vma->vm_truncate_count)
+ new_vma->vm_truncate_count = 0;
+ }
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * pte locks because exclusive mmap_sem prevents deadlock.
+ */
+ old_pte = pte_offset_map_lock(mm, old_pmd, old_end-1, &old_ptl);
+ new_pte = pte_offset_map_nested(new_pmd, new_end-1);
+ new_ptl = pte_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+ arch_enter_lazy_mmu_mode();
+
+ for (; old_end > old_addr; old_pte--, old_end -= PAGE_SIZE,
+ new_pte--, new_end -= PAGE_SIZE) {
+ if (pte_none(*old_pte))
+ continue;
+ pte = ptep_clear_flush(vma, old_end-1, old_pte);
+ pte = move_pte(pte, new_vma->vm_page_prot, old_end-1, new_end-1);
+ set_pte_at(mm, new_end-1, new_pte, pte);
+ }
+
+ arch_leave_lazy_mmu_mode();
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ pte_unmap_nested(new_pte - 1);
+ pte_unmap_unlock(old_pte - 1, old_ptl);
+ if (mapping)
+ spin_unlock(&mapping->i_mmap_lock);
+}
+
#define LATENCY_LIMIT (64 * PAGE_SIZE)

-static unsigned long move_page_tables(struct vm_area_struct *vma,
+unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len)
{
@@ -132,21 +186,25 @@ static unsigned long move_page_tables(st

for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
cond_resched();
+
next = (old_addr + PMD_SIZE) & PMD_MASK;
if (next - 1 > old_end)
next = old_end;
extent = next - old_addr;
+
old_pmd = get_old_pmd(vma->vm_mm, old_addr);
if (!old_pmd)
continue;
new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
if (!new_pmd)
break;
+
next = (new_addr + PMD_SIZE) & PMD_MASK;
if (extent > next - new_addr)
extent = next - new_addr;
if (extent > LATENCY_LIMIT)
extent = LATENCY_LIMIT;
+
move_ptes(vma, old_pmd, old_addr, old_addr + extent,
new_vma, new_pmd, new_addr);
}
@@ -154,6 +212,51 @@ static unsigned long move_page_tables(st
return len + old_addr - old_end; /* how much done */
}

+unsigned long move_page_tables_up(struct vm_area_struct *vma,
+ unsigned long old_addr, struct vm_area_struct *new_vma,
+ unsigned long new_addr, unsigned long len)
+{
+ unsigned long extent, prev, old_end, new_end;
+ pmd_t *old_pmd, *new_pmd;
+
+ old_end = old_addr + len;
+ new_end = new_addr + len;
+ flush_cache_range(vma, old_addr, old_end);
+
+ for (; old_end > old_addr; old_end -= extent, new_end -= extent) {
+ cond_resched();
+
+ /*
+ * calculate how far till prev PMD boundary for old
+ */
+ prev = (old_end - 1) & PMD_MASK;
+ if (prev < old_addr)
+ prev = old_addr;
+ extent = old_end - prev;
+
+ old_pmd = get_old_pmd(vma->vm_mm, old_end-1);
+ if (!old_pmd)
+ continue;
+ new_pmd = alloc_new_pmd(vma->vm_mm, new_end-1);
+ if (!new_pmd)
+ break;
+
+ /*
+ * calculate and clip to prev PMD boundary for new
+ */
+ prev = (new_end - 1) & PMD_MASK;
+ if (extent > new_end - prev)
+ extent = new_end - prev;
+ if (extent > LATENCY_LIMIT)
+ extent = LATENCY_LIMIT;
+
+ move_ptes_up(vma, old_pmd, old_end - extent, old_end,
+ new_vma, new_pmd, new_end - extent);
+ }
+
+ return old_addr + len - old_end;
+}
+
static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long old_len,
unsigned long new_len, unsigned long new_addr)
--

-
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