Btrfs: Fix a number of inline extent problems that Yan Zheng reported.

The fixes do a number of things:

1) Most btrfs_drop_extent callers will try to leave the inline extents in
place.  It can truncate bytes off the beginning of the inline extent if
required.

2) writepage can now update the inline extent, allowing mmap writes to
go directly into the inline extent.

3) btrfs_truncate_in_transaction truncates inline extents

4) extent_map.c fixed to not merge inline extent mappings and hole
mappings together

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

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);