1 files changed, 9 insertions, 1 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6b3e4404dc6a..1ace6d11e097 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -686,6 +686,7 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
         if ((offset & (blocksize - 1)) == 0)
                 goto out;
 
+        down_read(&BTRFS_I(inode)->root->snap_sem);
         ret = -ENOMEM;
         page = grab_cache_page(mapping, index);
         if (!page)
@@ -704,6 +705,7 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
 
         unlock_page(page);
         page_cache_release(page);
+        up_read(&BTRFS_I(inode)->root->snap_sem);
 out:
         return ret;
 }
@@ -1668,6 +1670,7 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
         int ret = -EINVAL;
         u64 page_start;
 
+        down_read(&BTRFS_I(inode)->root->snap_sem);
         lock_page(page);
         wait_on_page_writeback(page);
         size = i_size_read(inode);
@@ -1688,6 +1691,7 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
         ret = btrfs_cow_one_page(inode, page, end);
 
 out_unlock:
+        up_read(&BTRFS_I(inode)->root->snap_sem);
         unlock_page(page);
         return ret;
 }
@@ -1851,6 +1855,10 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
         if (!root->ref_cows)
                 return -EINVAL;
 
+        down_write(&root->snap_sem);
+        freeze_bdev(root->fs_info->sb->s_bdev);
+        thaw_bdev(root->fs_info->sb->s_bdev, root->fs_info->sb);
+
         mutex_lock(&root->fs_info->fs_mutex);
         trans = btrfs_start_transaction(root, 1);
         BUG_ON(!trans);
@@ -1894,12 +1902,12 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
         ret = btrfs_inc_root_ref(trans, root);
         if (ret)
                 goto fail;
-
 fail:
         err = btrfs_commit_transaction(trans, root);
         if (err && !ret)
                 ret = err;
         mutex_unlock(&root->fs_info->fs_mutex);
+        up_write(&root->snap_sem);
         btrfs_btree_balance_dirty(root);
         return ret;
 }