1 files changed, 46 insertions, 6 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 516b90224a1b..eef9c92f86d5 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1930,7 +1930,7 @@ again:
 int btrfs_truncate_item(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root,
                         struct btrfs_path *path,
-                        u32 new_size)
+                        u32 new_size, int from_end)
 {
         int ret = 0;
         int slot;
@@ -1946,13 +1946,17 @@ int btrfs_truncate_item(struct btrfs_trans_handle *trans,
 
         slot_orig = path->slots[0];
         leaf = path->nodes[0];
+        slot = path->slots[0];
+
+        old_size = btrfs_item_size_nr(leaf, slot);
+        if (old_size == new_size)
+                return 0;
 
         nritems = btrfs_header_nritems(leaf);
         data_end = leaf_data_end(root, leaf);
 
-        slot = path->slots[0];
         old_data_start = btrfs_item_offset_nr(leaf, slot);
-        old_size = btrfs_item_size_nr(leaf, slot); BUG_ON(old_size <= new_size);
+
         size_diff = old_size - new_size;
 
         BUG_ON(slot < 0);
@@ -1984,9 +1988,45 @@ int btrfs_truncate_item(struct btrfs_trans_handle *trans,
         }
 
         /* shift the data */
-        memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
-                      data_end + size_diff, btrfs_leaf_data(leaf) +
-                      data_end, old_data_start + new_size - data_end);
+        if (from_end) {
+                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
+                              data_end + size_diff, btrfs_leaf_data(leaf) +
+                              data_end, old_data_start + new_size - data_end);
+        } else {
+                struct btrfs_disk_key disk_key;
+                u64 offset;
+
+                btrfs_item_key(leaf, &disk_key, slot);
+
+                if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
+                        unsigned long ptr;
+                        struct btrfs_file_extent_item *fi;
+
+                        fi = btrfs_item_ptr(leaf, slot,
+                                            struct btrfs_file_extent_item);
+                        fi = (struct btrfs_file_extent_item *)(
+                             (unsigned long)fi - size_diff);
+
+                        if (btrfs_file_extent_type(leaf, fi) ==
+                            BTRFS_FILE_EXTENT_INLINE) {
+                                ptr = btrfs_item_ptr_offset(leaf, slot);
+                                memmove_extent_buffer(leaf, ptr,
+                                        (unsigned long)fi,
+                                        offsetof(struct btrfs_file_extent_item,
+                                                 disk_bytenr));
+                        }
+                }
+
+                memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
+                              data_end + size_diff, btrfs_leaf_data(leaf) +
+                              data_end, old_data_start - data_end);
+
+                offset = btrfs_disk_key_offset(&disk_key);
+                btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
+                btrfs_set_item_key(leaf, &disk_key, slot);
+                if (slot == 0)
+                        fixup_low_keys(trans, root, path, &disk_key, 1);
+        }
 
         item = btrfs_item_nr(leaf, slot);
         btrfs_set_item_size(leaf, item, new_size);