1 files changed, 306 insertions, 144 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index 08e3c7f2bd1..05f1180e9f2 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -3,26 +3,31 @@
  *
  *	(C) Copyright 1996 Linus Torvalds
  *
- *	Address space accounting code	<alan@redhat.com>
+ *	Address space accounting code	<alan@lxorguk.ukuu.org.uk>
  *	(C) Copyright 2002 Red Hat Inc, All Rights Reserved
  */
 
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
-#include <linux/slab.h>
 #include <linux/shm.h>
+#include <linux/ksm.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
 #include <linux/capability.h>
 #include <linux/fs.h>
+#include <linux/swapops.h>
 #include <linux/highmem.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/mmu_notifier.h>
+#include <linux/sched/sysctl.h>
 
 #include <asm/uaccess.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
+#include "internal.h"
+
 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;
@@ -38,13 +43,14 @@ static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 		return NULL;
 
 	pmd = pmd_offset(pud, addr);
-	if (pmd_none_or_clear_bad(pmd))
+	if (pmd_none(*pmd))
 		return NULL;
 
 	return pmd;
 }
 
-static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
+static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
+			    unsigned long addr)
 {
 	pgd_t *pgd;
 	pud_t *pud;
@@ -59,34 +65,66 @@ static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
 	if (!pmd)
 		return NULL;
 
-	if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
-		return NULL;
+	VM_BUG_ON(pmd_trans_huge(*pmd));
 
 	return pmd;
 }
 
+static pte_t move_soft_dirty_pte(pte_t pte)
+{
+	/*
+	 * Set soft dirty bit so we can notice
+	 * in userspace the ptes were moved.
+	 */
+#ifdef CONFIG_MEM_SOFT_DIRTY
+	if (pte_present(pte))
+		pte = pte_mksoft_dirty(pte);
+	else if (is_swap_pte(pte))
+		pte = pte_swp_mksoft_dirty(pte);
+	else if (pte_file(pte))
+		pte = pte_file_mksoft_dirty(pte);
+#endif
+	return pte;
+}
+
 static void move_ptes(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)
+		unsigned long new_addr, bool need_rmap_locks)
 {
 	struct address_space *mapping = NULL;
+	struct anon_vma *anon_vma = NULL;
 	struct mm_struct *mm = vma->vm_mm;
 	pte_t *old_pte, *new_pte, pte;
 	spinlock_t *old_ptl, *new_ptl;
 
-	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;
+	/*
+	 * When need_rmap_locks is true, we take the i_mmap_mutex and anon_vma
+	 * locks to ensure that rmap will always observe either the old or the
+	 * new ptes. This is the easiest way to avoid races with
+	 * truncate_pagecache(), page migration, etc...
+	 *
+	 * When need_rmap_locks is false, we use other ways to avoid
+	 * such races:
+	 *
+	 * - During exec() shift_arg_pages(), we use a specially tagged vma
+	 *   which rmap call sites look for using is_vma_temporary_stack().
+	 *
+	 * - During mremap(), new_vma is often known to be placed after vma
+	 *   in rmap traversal order. This ensures rmap will always observe
+	 *   either the old pte, or the new pte, or both (the page table locks
+	 *   serialize access to individual ptes, but only rmap traversal
+	 *   order guarantees that we won't miss both the old and new ptes).
+	 */
+	if (need_rmap_locks) {
+		if (vma->vm_file) {
+			mapping = vma->vm_file->f_mapping;
+			mutex_lock(&mapping->i_mmap_mutex);
+		}
+		if (vma->anon_vma) {
+			anon_vma = vma->anon_vma;
+			anon_vma_lock_write(anon_vma);
+		}
 	}
 
 	/*
@@ -94,7 +132,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 	 * pte locks because exclusive mmap_sem prevents deadlock.
 	 */
 	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
- 	new_pte = pte_offset_map_nested(new_pmd, new_addr);
+	new_pte = pte_offset_map(new_pmd, new_addr);
 	new_ptl = pte_lockptr(mm, new_pmd);
 	if (new_ptl != old_ptl)
 		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
@@ -104,59 +142,100 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 				   new_pte++, new_addr += PAGE_SIZE) {
 		if (pte_none(*old_pte))
 			continue;
-		pte = ptep_clear_flush(vma, old_addr, old_pte);
+		pte = ptep_get_and_clear(mm, old_addr, old_pte);
 		pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
+		pte = move_soft_dirty_pte(pte);
 		set_pte_at(mm, new_addr, 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(new_pte - 1);
 	pte_unmap_unlock(old_pte - 1, old_ptl);
+	if (anon_vma)
+		anon_vma_unlock_write(anon_vma);
 	if (mapping)
-		spin_unlock(&mapping->i_mmap_lock);
+		mutex_unlock(&mapping->i_mmap_mutex);
 }
 
 #define LATENCY_LIMIT	(64 * PAGE_SIZE)
 
 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)
+		unsigned long new_addr, unsigned long len,
+		bool need_rmap_locks)
 {
 	unsigned long extent, next, old_end;
 	pmd_t *old_pmd, *new_pmd;
+	bool need_flush = false;
+	unsigned long mmun_start;	/* For mmu_notifiers */
+	unsigned long mmun_end;		/* For mmu_notifiers */
 
 	old_end = old_addr + len;
 	flush_cache_range(vma, old_addr, old_end);
 
+	mmun_start = old_addr;
+	mmun_end   = old_end;
+	mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
+
 	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;
+		/* even if next overflowed, extent below will be ok */
 		extent = next - old_addr;
+		if (extent > old_end - old_addr)
+			extent = old_end - 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);
+		new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
 		if (!new_pmd)
 			break;
+		if (pmd_trans_huge(*old_pmd)) {
+			int err = 0;
+			if (extent == HPAGE_PMD_SIZE) {
+				VM_BUG_ON(vma->vm_file || !vma->anon_vma);
+				/* See comment in move_ptes() */
+				if (need_rmap_locks)
+					anon_vma_lock_write(vma->anon_vma);
+				err = move_huge_pmd(vma, new_vma, old_addr,
+						    new_addr, old_end,
+						    old_pmd, new_pmd);
+				if (need_rmap_locks)
+					anon_vma_unlock_write(vma->anon_vma);
+			}
+			if (err > 0) {
+				need_flush = true;
+				continue;
+			} else if (!err) {
+				split_huge_page_pmd(vma, old_addr, old_pmd);
+			}
+			VM_BUG_ON(pmd_trans_huge(*old_pmd));
+		}
+		if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
+						      new_pmd, new_addr))
+			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);
+			  new_vma, new_pmd, new_addr, need_rmap_locks);
+		need_flush = true;
 	}
+	if (likely(need_flush))
+		flush_tlb_range(vma, old_end-len, old_addr);
+
+	mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
 
 	return len + old_addr - old_end;	/* how much done */
 }
 
 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)
+		unsigned long new_len, unsigned long new_addr, bool *locked)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_area_struct *new_vma;
@@ -166,6 +245,8 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 	unsigned long excess = 0;
 	unsigned long hiwater_vm;
 	int split = 0;
+	int err;
+	bool need_rmap_locks;
 
 	/*
 	 * We'd prefer to avoid failure later on in do_munmap:
@@ -174,19 +255,34 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 	if (mm->map_count >= sysctl_max_map_count - 3)
 		return -ENOMEM;
 
+	/*
+	 * Advise KSM to break any KSM pages in the area to be moved:
+	 * it would be confusing if they were to turn up at the new
+	 * location, where they happen to coincide with different KSM
+	 * pages recently unmapped.  But leave vma->vm_flags as it was,
+	 * so KSM can come around to merge on vma and new_vma afterwards.
+	 */
+	err = ksm_madvise(vma, old_addr, old_addr + old_len,
+						MADV_UNMERGEABLE, &vm_flags);
+	if (err)
+		return err;
+
 	new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
-	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
+	new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
+			   &need_rmap_locks);
 	if (!new_vma)
 		return -ENOMEM;
 
-	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
+	moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
+				     need_rmap_locks);
 	if (moved_len < old_len) {
 		/*
 		 * On error, move entries back from new area to old,
 		 * which will succeed since page tables still there,
 		 * and then proceed to unmap new area instead of old.
 		 */
-		move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
+		move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
+				 true);
 		vma = new_vma;
 		old_len = new_len;
 		old_addr = new_addr;
@@ -212,7 +308,6 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 	 * If this were a serious issue, we'd add a flag to do_munmap().
 	 */
 	hiwater_vm = mm->hiwater_vm;
-	mm->total_vm += new_len >> PAGE_SHIFT;
 	vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
 
 	if (do_munmap(mm, old_addr, old_len) < 0) {
@@ -231,14 +326,145 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 
 	if (vm_flags & VM_LOCKED) {
 		mm->locked_vm += new_len >> PAGE_SHIFT;
-		if (new_len > old_len)
-			make_pages_present(new_addr + old_len,
-					   new_addr + new_len);
+		*locked = true;
 	}
 
 	return new_addr;
 }
 
+static struct vm_area_struct *vma_to_resize(unsigned long addr,
+	unsigned long old_len, unsigned long new_len, unsigned long *p)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma = find_vma(mm, addr);
+
+	if (!vma || vma->vm_start > addr)
+		goto Efault;
+
+	if (is_vm_hugetlb_page(vma))
+		goto Einval;
+
+	/* We can't remap across vm area boundaries */
+	if (old_len > vma->vm_end - addr)
+		goto Efault;
+
+	/* Need to be careful about a growing mapping */
+	if (new_len > old_len) {
+		unsigned long pgoff;
+
+		if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
+			goto Efault;
+		pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
+		pgoff += vma->vm_pgoff;
+		if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
+			goto Einval;
+	}
+
+	if (vma->vm_flags & VM_LOCKED) {
+		unsigned long locked, lock_limit;
+		locked = mm->locked_vm << PAGE_SHIFT;
+		lock_limit = rlimit(RLIMIT_MEMLOCK);
+		locked += new_len - old_len;
+		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+			goto Eagain;
+	}
+
+	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
+		goto Enomem;
+
+	if (vma->vm_flags & VM_ACCOUNT) {
+		unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
+		if (security_vm_enough_memory_mm(mm, charged))
+			goto Efault;
+		*p = charged;
+	}
+
+	return vma;
+
+Efault:	/* very odd choice for most of the cases, but... */
+	return ERR_PTR(-EFAULT);
+Einval:
+	return ERR_PTR(-EINVAL);
+Enomem:
+	return ERR_PTR(-ENOMEM);
+Eagain:
+	return ERR_PTR(-EAGAIN);
+}
+
+static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
+		unsigned long new_addr, unsigned long new_len, bool *locked)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	unsigned long ret = -EINVAL;
+	unsigned long charged = 0;
+	unsigned long map_flags;
+
+	if (new_addr & ~PAGE_MASK)
+		goto out;
+
+	if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
+		goto out;
+
+	/* Check if the location we're moving into overlaps the
+	 * old location at all, and fail if it does.
+	 */
+	if ((new_addr <= addr) && (new_addr+new_len) > addr)
+		goto out;
+
+	if ((addr <= new_addr) && (addr+old_len) > new_addr)
+		goto out;
+
+	ret = do_munmap(mm, new_addr, new_len);
+	if (ret)
+		goto out;
+
+	if (old_len >= new_len) {
+		ret = do_munmap(mm, addr+new_len, old_len - new_len);
+		if (ret && old_len != new_len)
+			goto out;
+		old_len = new_len;
+	}
+
+	vma = vma_to_resize(addr, old_len, new_len, &charged);
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
+		goto out;
+	}
+
+	map_flags = MAP_FIXED;
+	if (vma->vm_flags & VM_MAYSHARE)
+		map_flags |= MAP_SHARED;
+
+	ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
+				((addr - vma->vm_start) >> PAGE_SHIFT),
+				map_flags);
+	if (ret & ~PAGE_MASK)
+		goto out1;
+
+	ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
+	if (!(ret & ~PAGE_MASK))
+		goto out;
+out1:
+	vm_unacct_memory(charged);
+
+out:
+	return ret;
+}
+
+static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
+{
+	unsigned long end = vma->vm_end + delta;
+	if (end < vma->vm_end) /* overflow */
+		return 0;
+	if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
+		return 0;
+	if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
+			      0, MAP_FIXED) & ~PAGE_MASK)
+		return 0;
+	return 1;
+}
+
 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
@@ -246,20 +472,24 @@ static unsigned long move_vma(struct vm_area_struct *vma,
  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
  * This option implies MREMAP_MAYMOVE.
  */
-unsigned long do_mremap(unsigned long addr,
-	unsigned long old_len, unsigned long new_len,
-	unsigned long flags, unsigned long new_addr)
+SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
+		unsigned long, new_len, unsigned long, flags,
+		unsigned long, new_addr)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long ret = -EINVAL;
 	unsigned long charged = 0;
+	bool locked = false;
 
 	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
-		goto out;
+		return ret;
+
+	if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
+		return ret;
 
 	if (addr & ~PAGE_MASK)
-		goto out;
+		return ret;
 
 	old_len = PAGE_ALIGN(old_len);
 	new_len = PAGE_ALIGN(new_len);
@@ -270,34 +500,14 @@ unsigned long do_mremap(unsigned long addr,
 	 * a zero new-len is nonsensical.
 	 */
 	if (!new_len)
-		goto out;
-
-	/* new_addr is only valid if MREMAP_FIXED is specified */
-	if (flags & MREMAP_FIXED) {
-		if (new_addr & ~PAGE_MASK)
-			goto out;
-		if (!(flags & MREMAP_MAYMOVE))
-			goto out;
-
-		if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
-			goto out;
-
-		/* Check if the location we're moving into overlaps the
-		 * old location at all, and fail if it does.
-		 */
-		if ((new_addr <= addr) && (new_addr+new_len) > addr)
-			goto out;
+		return ret;
 
-		if ((addr <= new_addr) && (addr+old_len) > new_addr)
-			goto out;
-
-		ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-		if (ret)
-			goto out;
+	down_write(&current->mm->mmap_sem);
 
-		ret = do_munmap(mm, new_addr, new_len);
-		if (ret)
-			goto out;
+	if (flags & MREMAP_FIXED) {
+		ret = mremap_to(addr, old_len, new_addr, new_len,
+				&locked);
+		goto out;
 	}
 
 	/*
@@ -310,71 +520,36 @@ unsigned long do_mremap(unsigned long addr,
 		if (ret && old_len != new_len)
 			goto out;
 		ret = addr;
-		if (!(flags & MREMAP_FIXED) || (new_addr == addr))
-			goto out;
-		old_len = new_len;
+		goto out;
 	}
 
 	/*
-	 * Ok, we need to grow..  or relocate.
+	 * Ok, we need to grow..
 	 */
-	ret = -EFAULT;
-	vma = find_vma(mm, addr);
-	if (!vma || vma->vm_start > addr)
-		goto out;
-	if (is_vm_hugetlb_page(vma)) {
-		ret = -EINVAL;
-		goto out;
-	}
-	/* We can't remap across vm area boundaries */
-	if (old_len > vma->vm_end - addr)
-		goto out;
-	if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
-		if (new_len > old_len)
-			goto out;
-	}
-	if (vma->vm_flags & VM_LOCKED) {
-		unsigned long locked, lock_limit;
-		locked = mm->locked_vm << PAGE_SHIFT;
-		lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
-		locked += new_len - old_len;
-		ret = -EAGAIN;
-		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
-			goto out;
-	}
-	if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
-		ret = -ENOMEM;
+	vma = vma_to_resize(addr, old_len, new_len, &charged);
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
 		goto out;
 	}
 
-	if (vma->vm_flags & VM_ACCOUNT) {
-		charged = (new_len - old_len) >> PAGE_SHIFT;
-		if (security_vm_enough_memory(charged))
-			goto out_nc;
-	}
-
 	/* old_len exactly to the end of the area..
-	 * And we're not relocating the area.
 	 */
-	if (old_len == vma->vm_end - addr &&
-	    !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
-	    (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
-		unsigned long max_addr = TASK_SIZE;
-		if (vma->vm_next)
-			max_addr = vma->vm_next->vm_start;
+	if (old_len == vma->vm_end - addr) {
 		/* can we just expand the current mapping? */
-		if (max_addr - addr >= new_len) {
+		if (vma_expandable(vma, new_len - old_len)) {
 			int pages = (new_len - old_len) >> PAGE_SHIFT;
 
-			vma_adjust(vma, vma->vm_start,
-				addr + new_len, vma->vm_pgoff, NULL);
+			if (vma_adjust(vma, vma->vm_start, addr + new_len,
+				       vma->vm_pgoff, NULL)) {
+				ret = -ENOMEM;
+				goto out;
+			}
 
-			mm->total_vm += pages;
 			vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
 			if (vma->vm_flags & VM_LOCKED) {
 				mm->locked_vm += pages;
-				make_pages_present(addr + old_len,
-						   addr + new_len);
+				locked = true;
+				new_addr = addr;
 			}
 			ret = addr;
 			goto out;
@@ -387,39 +562,26 @@ unsigned long do_mremap(unsigned long addr,
 	 */
 	ret = -ENOMEM;
 	if (flags & MREMAP_MAYMOVE) {
-		if (!(flags & MREMAP_FIXED)) {
-			unsigned long map_flags = 0;
-			if (vma->vm_flags & VM_MAYSHARE)
-				map_flags |= MAP_SHARED;
-
-			new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
-						vma->vm_pgoff, map_flags);
-			if (new_addr & ~PAGE_MASK) {
-				ret = new_addr;
-				goto out;
-			}
-
-			ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
-			if (ret)
-				goto out;
+		unsigned long map_flags = 0;
+		if (vma->vm_flags & VM_MAYSHARE)
+			map_flags |= MAP_SHARED;
+
+		new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
+					vma->vm_pgoff +
+					((addr - vma->vm_start) >> PAGE_SHIFT),
+					map_flags);
+		if (new_addr & ~PAGE_MASK) {
+			ret = new_addr;
+			goto out;
 		}
-		ret = move_vma(vma, addr, old_len, new_len, new_addr);
+
+		ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
 	}
 out:
 	if (ret & ~PAGE_MASK)
 		vm_unacct_memory(charged);
-out_nc:
-	return ret;
-}
-
-asmlinkage unsigned long sys_mremap(unsigned long addr,
-	unsigned long old_len, unsigned long new_len,
-	unsigned long flags, unsigned long new_addr)
-{
-	unsigned long ret;
-
-	down_write(&current->mm->mmap_sem);
-	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
 	up_write(&current->mm->mmap_sem);
+	if (locked && new_len > old_len)
+		mm_populate(new_addr + old_len, new_len - old_len);
 	return ret;
 }