Btrfs: btrfs_mark_extent_written uses the wrong slot

My test do: fallocate a big file and do write. The file is 512M, but
after file write is done btrfs-debug-tree shows:
item 6 key (257 EXTENT_DATA 0) itemoff 3516 itemsize 53
                extent data disk byte 1103101952 nr 536870912
                extent data offset 0 nr 399634432 ram 536870912
                extent compression 0
Looks like a regression introducted by
6c7d54ac87f338c479d9729e8392eca3f76e11e1, where we set wrong slot.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 413a30dafcda..a7fd9f3a750a 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -720,13 +720,15 @@ again:
                                         inode->i_ino, orig_offset);
                 BUG_ON(ret);
         }
-        fi = btrfs_item_ptr(leaf, path->slots[0],
-                           struct btrfs_file_extent_item);
         if (del_nr == 0) {
+                fi = btrfs_item_ptr(leaf, path->slots[0],
+                           struct btrfs_file_extent_item);
                 btrfs_set_file_extent_type(leaf, fi,
                                            BTRFS_FILE_EXTENT_REG);
                 btrfs_mark_buffer_dirty(leaf);
         } else {
+                fi = btrfs_item_ptr(leaf, del_slot - 1,
+                           struct btrfs_file_extent_item);
                 btrfs_set_file_extent_type(leaf, fi,
                                            BTRFS_FILE_EXTENT_REG);
                 btrfs_set_file_extent_num_bytes(leaf, fi,