btrfs-progs: add shift_items to btrfs-corrupt-block

A user had a corrupted fs where his items where shifted oddly.  This adds the
functionality I needed to btrfs-corrupt-block in order to reproduce this
corruption in order to make fsck fix this sort of problem.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

diff --git a/btrfs-corrupt-block.c b/btrfs-corrupt-block.c
index 15f1082..171c81d 100644 (file)
--- a/btrfs-corrupt-block.c
+++ b/btrfs-corrupt-block.c
@@ -312,6 +312,7 @@ enum btrfs_dir_item_field {
 
 enum btrfs_metadata_block_field {
        BTRFS_METADATA_BLOCK_GENERATION,
+       BTRFS_METADATA_BLOCK_SHIFT_ITEMS,
        BTRFS_METADATA_BLOCK_BAD,
 };
 
@@ -346,6 +347,8 @@ convert_metadata_block_field(char *field)
 {
        if (!strncmp(field, "generation", FIELD_BUF_LEN))
                return BTRFS_METADATA_BLOCK_GENERATION;
+       if (!strncmp(field, "shift_items", FIELD_BUF_LEN))
+               return BTRFS_METADATA_BLOCK_SHIFT_ITEMS;
        return BTRFS_METADATA_BLOCK_BAD;
 }
 
@@ -651,6 +654,27 @@ out:
        return ret;
 }
 
+static void shift_items(struct btrfs_root *root, struct extent_buffer *eb)
+{
+       int nritems = btrfs_header_nritems(eb);
+       int shift_space = btrfs_leaf_free_space(root, eb) / 2;
+       int slot = nritems / 2;
+       int i = 0;
+       unsigned int data_end = btrfs_item_offset_nr(eb, nritems - 1);
+
+       /* Shift the item data up to and including slot back by shift space */
+       memmove_extent_buffer(eb, btrfs_leaf_data(eb) + data_end - shift_space,
+                             btrfs_leaf_data(eb) + data_end,
+                             btrfs_item_offset_nr(eb, slot - 1) - data_end);
+
+       /* Now update the item pointers. */
+       for (i = nritems - 1; i >= slot; i--) {
+               u32 offset = btrfs_item_offset_nr(eb, i);
+               offset -= shift_space;
+               btrfs_set_item_offset(eb, btrfs_item_nr(i), offset);
+       }
+}
+
 static int corrupt_metadata_block(struct btrfs_root *root, u64 block,
                                  char *field)
 {
@@ -721,6 +745,9 @@ static int corrupt_metadata_block(struct btrfs_root *root, u64 block,
                bogus = generate_u64(orig);
                btrfs_set_header_generation(eb, bogus);
                break;
+       case BTRFS_METADATA_BLOCK_SHIFT_ITEMS:
+               shift_items(root, path->nodes[level]);
+               break;
        default:
                ret = -EINVAL;
                break;