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-rw-r--r--arch/Kconfig5
-rw-r--r--mm/mremap.c64
2 files changed, 69 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index e1e540ffa979..b70c952ac838 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -535,6 +535,11 @@ config HAVE_IRQ_TIME_ACCOUNTING
Archs need to ensure they use a high enough resolution clock to
support irq time accounting and then call enable_sched_clock_irqtime().
+config HAVE_MOVE_PMD
+ bool
+ help
+ Archs that select this are able to move page tables at the PMD level.
+
config HAVE_ARCH_TRANSPARENT_HUGEPAGE
bool
diff --git a/mm/mremap.c b/mm/mremap.c
index fc3f92962a7e..3320616ed93f 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -191,6 +191,52 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
drop_rmap_locks(vma);
}
+#ifdef CONFIG_HAVE_MOVE_PMD
+static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
+ unsigned long new_addr, unsigned long old_end,
+ pmd_t *old_pmd, pmd_t *new_pmd)
+{
+ spinlock_t *old_ptl, *new_ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ pmd_t pmd;
+
+ if ((old_addr & ~PMD_MASK) || (new_addr & ~PMD_MASK)
+ || old_end - old_addr < PMD_SIZE)
+ return false;
+
+ /*
+ * The destination pmd shouldn't be established, free_pgtables()
+ * should have release it.
+ */
+ if (WARN_ON(!pmd_none(*new_pmd)))
+ return false;
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * ptlocks because exclusive mmap_sem prevents deadlock.
+ */
+ old_ptl = pmd_lock(vma->vm_mm, old_pmd);
+ new_ptl = pmd_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+
+ /* Clear the pmd */
+ pmd = *old_pmd;
+ pmd_clear(old_pmd);
+
+ VM_BUG_ON(!pmd_none(*new_pmd));
+
+ /* Set the new pmd */
+ set_pmd_at(mm, new_addr, new_pmd, pmd);
+ flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ spin_unlock(old_ptl);
+
+ return true;
+}
+#endif
+
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,
@@ -235,7 +281,25 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
split_huge_pmd(vma, old_pmd, old_addr);
if (pmd_trans_unstable(old_pmd))
continue;
+ } else if (extent == PMD_SIZE) {
+#ifdef CONFIG_HAVE_MOVE_PMD
+ /*
+ * If the extent is PMD-sized, try to speed the move by
+ * moving at the PMD level if possible.
+ */
+ bool moved;
+
+ if (need_rmap_locks)
+ take_rmap_locks(vma);
+ moved = move_normal_pmd(vma, old_addr, new_addr,
+ old_end, old_pmd, new_pmd);
+ if (need_rmap_locks)
+ drop_rmap_locks(vma);
+ if (moved)
+ continue;
+#endif
}
+
if (pte_alloc(new_vma->vm_mm, new_pmd))
break;
next = (new_addr + PMD_SIZE) & PMD_MASK;