From 3fa1c4a69c8d7611a32dab7f519c321ced28c644 Mon Sep 17 00:00:00 2001
From: t_jeang <devnull@localhost>
Date: Tue, 6 Jan 2009 12:06:01 +0000
Subject: [PATCH] imported patch CA-20346-blktap-vma-unmap

---
 drivers/xen/blktap/blktap.c | 25 +++++++++++++++++++++++--
 include/linux/mm.h          |  4 ++++
 mm/mmap.c                   | 12 +++++++++++-
 3 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/blktap/blktap.c b/drivers/xen/blktap/blktap.c
index 3729c160..87cb9df9 100644
--- a/drivers/xen/blktap/blktap.c
+++ b/drivers/xen/blktap/blktap.c
@@ -93,6 +93,12 @@ static unsigned short mmap_alloc = 0;
 static unsigned short mmap_lock = 0;
 static unsigned short mmap_inuse = 0;
 
+#define BLKTAP_VMA_MAPPED 5
+static inline int blktap_vma_mapped(struct tap_blkif *info)
+{
+	return test_bit(BLKTAP_VMA_MAPPED, &info->dev_inuse);
+}
+
 /******************************************************************
  * GRANT HANDLES
  */
@@ -236,13 +242,20 @@ static pte_t blktap_clear_pte(struct vm_area_struct *vma,
 	return copy;
 }
 
-static void blktap_vm_close(struct vm_area_struct *vma)
+static void blktap_vm_unmap(struct vm_area_struct *vma)
 {
 	struct tap_blkif *info = vma->vm_private_data;
 
 	down_write(&info->vm_update_sem);
+	clear_bit(BLKTAP_VMA_MAPPED, &info->dev_inuse);
+	up_write(&info->vm_update_sem);
+}
 
-	zap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, NULL);
+static void blktap_vm_close(struct vm_area_struct *vma)
+{
+	struct tap_blkif *info = vma->vm_private_data;
+
+	down_write(&info->vm_update_sem);
 
 	kfree(info->foreign_map.map);
 
@@ -260,6 +273,7 @@ static void blktap_vm_close(struct vm_area_struct *vma)
 
 static 
 struct vm_operations_struct blktap_vm_ops = {
+	unmap:    blktap_vm_unmap,
 	close:    blktap_vm_close,
 	nopage:   blktap_nopage,
 	zap_pte:  blktap_clear_pte,
@@ -535,6 +549,7 @@ static int blktap_mmap(struct file *filp, struct vm_area_struct *vma)
 	info->pid = current->pid;
 	DPRINTK("blktap: mapping pid is %d\n", info->pid);
 
+	set_bit(BLKTAP_VMA_MAPPED, &info->dev_inuse);
 	info->vma = vma;
 	return 0;
 
@@ -945,6 +960,12 @@ int tap_blkif_schedule(void *arg)
 			break;
 		}
 
+		if (!blktap_vma_mapped(info)) {
+			WPRINTK("vma unmapped but not closed\n");
+			up_read(&info->vm_update_sem);
+			continue;
+		}
+
 		if (do_block_io_op(info))
 			blkif->waiting_reqs = 1;
 		else
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b5c8fc76..f0c8c3ff 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -220,6 +220,10 @@ struct vm_operations_struct {
 	 * original value of @ptep. */
 	pte_t (*zap_pte)(struct vm_area_struct *vma, 
 			 unsigned long addr, pte_t *ptep, int is_fullmm);
+
+	/* called before close() to indicate no more pages should be mapped */
+	void (*unmap)(struct vm_area_struct *area);
+
 #ifdef CONFIG_NUMA
 	int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);
 	struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
diff --git a/mm/mmap.c b/mm/mmap.c
index dabff0b8..4b7c04cd 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1787,6 +1787,12 @@ static void unmap_region(struct mm_struct *mm,
 	tlb_finish_mmu(tlb, start, end);
 }
 
+static inline void unmap_vma(struct vm_area_struct *vma)
+{
+	if (unlikely(vma->vm_ops && vma->vm_ops->unmap))
+		vma->vm_ops->unmap(vma);
+}
+
 /*
  * Create a list of vma's touched by the unmap, removing them from the mm's
  * vma list as we go..
@@ -1802,6 +1808,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
 	insertion_point = (prev ? &prev->vm_next : &mm->mmap);
 	do {
 		rb_erase(&vma->vm_rb, &mm->mm_rb);
+		unmap_vma(vma);
 		mm->map_count--;
 		tail_vma = vma;
 		vma = vma->vm_next;
@@ -2068,7 +2075,7 @@ EXPORT_SYMBOL(do_brk);
 void exit_mmap(struct mm_struct *mm)
 {
 	struct mmu_gather *tlb;
-	struct vm_area_struct *vma = mm->mmap;
+	struct vm_area_struct *vma_tmp, *vma = mm->mmap;
 	unsigned long nr_accounted = 0;
 	unsigned long end;
 
@@ -2076,6 +2083,9 @@ void exit_mmap(struct mm_struct *mm)
 	arch_exit_mmap(mm);
 #endif
 
+	for (vma_tmp = mm->mmap; vma_tmp; vma_tmp = vma_tmp->vm_next)
+		unmap_vma(vma_tmp);
+
 	lru_add_drain();
 	flush_cache_mm(mm);
 	tlb = tlb_gather_mmu(mm, 1);
-- 
2.39.5