Btrfs: make fsync work after cloning into a file

When cloning into a file, we were correctly replacing the extent
items in the target range and removing the extent maps. However
we weren't replacing the extent maps with new ones that point to
the new extents - as a consequence, an incremental fsync (when the
inode doesn't have the full sync flag) was a NOOP, since it relies
on the existence of extent maps in the modified list of the inode's
extent map tree, which was empty. Therefore add new extent maps to
reflect the target clone range.

A test case for xfstests follows.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index dd9a02a..c2e796b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3043,6 +3043,60 @@ out:
 	return ret;
 }
 
+static void clone_update_extent_map(struct inode *inode,
+				    const struct btrfs_trans_handle *trans,
+				    const struct btrfs_path *path,
+				    struct btrfs_file_extent_item *fi,
+				    const u64 hole_offset,
+				    const u64 hole_len)
+{
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct extent_map *em;
+	int ret;
+
+	em = alloc_extent_map();
+	if (!em) {
+		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			&BTRFS_I(inode)->runtime_flags);
+		return;
+	}
+
+	if (fi) {
+		btrfs_extent_item_to_extent_map(inode, path, fi, false, em);
+		em->generation = -1;
+		if (btrfs_file_extent_type(path->nodes[0], fi) ==
+		    BTRFS_FILE_EXTENT_INLINE)
+			set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+				&BTRFS_I(inode)->runtime_flags);
+	} else {
+		em->start = hole_offset;
+		em->len = hole_len;
+		em->ram_bytes = em->len;
+		em->orig_start = hole_offset;
+		em->block_start = EXTENT_MAP_HOLE;
+		em->block_len = 0;
+		em->orig_block_len = 0;
+		em->compress_type = BTRFS_COMPRESS_NONE;
+		em->generation = trans->transid;
+	}
+
+	while (1) {
+		write_lock(&em_tree->lock);
+		ret = add_extent_mapping(em_tree, em, 1);
+		write_unlock(&em_tree->lock);
+		if (ret != -EEXIST) {
+			free_extent_map(em);
+			break;
+		}
+		btrfs_drop_extent_cache(inode, em->start,
+					em->start + em->len - 1, 0);
+	}
+
+	if (unlikely(ret))
+		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
+			&BTRFS_I(inode)->runtime_flags);
+}
+
 /**
  * btrfs_clone() - clone a range from inode file to another
  *
@@ -3361,8 +3415,19 @@ process_slot:
 					    btrfs_item_ptr_offset(leaf, slot),
 					    size);
 				inode_add_bytes(inode, datal);
+				extent = btrfs_item_ptr(leaf, slot,
+						struct btrfs_file_extent_item);
 			}
 
+			/* If we have an implicit hole (NO_HOLES feature). */
+			if (drop_start < new_key.offset)
+				clone_update_extent_map(inode, trans,
+						path, NULL, drop_start,
+						new_key.offset - drop_start);
+
+			clone_update_extent_map(inode, trans, path,
+						extent, 0, 0);
+
 			btrfs_mark_buffer_dirty(leaf);
 			btrfs_release_path(path);
 
@@ -3406,6 +3471,10 @@ process_slot:
 		}
 		ret = clone_finish_inode_update(trans, inode, destoff + len,
 						destoff, olen);
+		if (ret)
+			goto out;
+		clone_update_extent_map(inode, trans, path, NULL, last_dest_end,
+					destoff + len - last_dest_end);
 	}
 
 out: