Deal with page == NULL in the btrfs_unplug_io_fn

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7f5aca35494d214bc80132902dc6a4e1583f2877..19c258d2c7e229e973f78b1249d3e8dd5d8000f5 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -911,12 +911,40 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits)
        return ret;
 }
 
+/*
+ * this unplugs every device on the box, and it is only used when page
+ * is null
+ */
+static void __unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
+{
+       struct list_head *cur;
+       struct btrfs_device *device;
+       struct btrfs_fs_info *info;
+
+       info = (struct btrfs_fs_info *)bdi->unplug_io_data;
+       list_for_each(cur, &info->fs_devices->devices) {
+               device = list_entry(cur, struct btrfs_device, dev_list);
+               bdi = blk_get_backing_dev_info(device->bdev);
+               if (bdi->unplug_io_fn) {
+                       bdi->unplug_io_fn(bdi, page);
+               }
+       }
+}
+
 void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
 {
-       struct inode *inode = page->mapping->host;
+       struct inode *inode;
        struct extent_map_tree *em_tree;
        struct extent_map *em;
-       u64 offset = page_offset(page);
+       u64 offset;
+
+       if (!page) {
+               __unplug_io_fn(bdi, page);
+               return;
+       }
+
+       inode = page->mapping->host;
+       offset = page_offset(page);
 
        em_tree = &BTRFS_I(inode)->extent_tree;
        spin_lock(&em_tree->lock);