btrfs: remove old tree_root dirent processing in btrfs_real_readdir()

Commit 3de4586c (Btrfs: Allow subvolumes and snapshots anywhere
in the directory tree) introduced the current system of placing
snapshots in the directory tree.  It also introduced the behavior of
creating the snapshot and then creating the directory entries for it.

We've kept this code around for compatibility reasons, but it turns
out that no file systems with the old tree_root based snapshots can
be mounted on newer (>= 2009) kernels anyway.  About a month after the
above commit, commit 2a7108ad (Btrfs: rev the disk format for the
inode compat and csum selection changes) landed, changing the superblock
magic number.

As a result, we know that we'll never encounter tree_root-based dirents
or have to deal with skipping our own snapshot dirents.  Since that
also means that we're now only iterating over DIR_INDEX items, which only
contain one directory entry per leaf item, we don't need to loop over
the leaf item contents anymore either.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -5804,20 +5804,13 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 	int slot;
 	unsigned char d_type;
 	int over = 0;
-	u32 di_cur;
-	u32 di_total;
-	u32 di_len;
-	int key_type = BTRFS_DIR_INDEX_KEY;
 	char tmp_name[32];
 	char *name_ptr;
 	int name_len;
 	int is_curr = 0;	/* ctx->pos points to the current index? */
 	bool emitted;
 	bool put = false;
-
-	/* FIXME, use a real flag for deciding about the key type */
-	if (root->fs_info->tree_root == root)
-		key_type = BTRFS_DIR_ITEM_KEY;
+	struct btrfs_key location;
 
 	if (!dir_emit_dots(file, ctx))
 		return 0;
@@ -5828,14 +5821,11 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 
 	path->reada = READA_FORWARD;
 
-	if (key_type == BTRFS_DIR_INDEX_KEY) {
-		INIT_LIST_HEAD(&ins_list);
-		INIT_LIST_HEAD(&del_list);
-		put = btrfs_readdir_get_delayed_items(inode, &ins_list,
-						      &del_list);
-	}
+	INIT_LIST_HEAD(&ins_list);
+	INIT_LIST_HEAD(&del_list);
+	put = btrfs_readdir_get_delayed_items(inode, &ins_list, &del_list);
 
-	key.type = key_type;
+	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = ctx->pos;
 	key.objectid = btrfs_ino(inode);
 
@@ -5861,85 +5851,54 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 
 		if (found_key.objectid != key.objectid)
 			break;
-		if (found_key.type != key_type)
+		if (found_key.type != BTRFS_DIR_INDEX_KEY)
 			break;
 		if (found_key.offset < ctx->pos)
 			goto next;
-		if (key_type == BTRFS_DIR_INDEX_KEY &&
-		    btrfs_should_delete_dir_index(&del_list,
-						  found_key.offset))
+		if (btrfs_should_delete_dir_index(&del_list, found_key.offset))
 			goto next;
 
 		ctx->pos = found_key.offset;
 		is_curr = 1;
 
 		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
-		di_cur = 0;
-		di_total = btrfs_item_size(leaf, item);
-
-		while (di_cur < di_total) {
-			struct btrfs_key location;
-
-			if (verify_dir_item(root, leaf, di))
-				break;
+		if (verify_dir_item(root, leaf, di))
+			goto next;
 
-			name_len = btrfs_dir_name_len(leaf, di);
-			if (name_len <= sizeof(tmp_name)) {
-				name_ptr = tmp_name;
-			} else {
-				name_ptr = kmalloc(name_len, GFP_KERNEL);
-				if (!name_ptr) {
-					ret = -ENOMEM;
-					goto err;
-				}
+		name_len = btrfs_dir_name_len(leaf, di);
+		if (name_len <= sizeof(tmp_name)) {
+			name_ptr = tmp_name;
+		} else {
+			name_ptr = kmalloc(name_len, GFP_KERNEL);
+			if (!name_ptr) {
+				ret = -ENOMEM;
+				goto err;
 			}
-			read_extent_buffer(leaf, name_ptr,
-					   (unsigned long)(di + 1), name_len);
-
-			d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
-			btrfs_dir_item_key_to_cpu(leaf, di, &location);
+		}
+		read_extent_buffer(leaf, name_ptr, (unsigned long)(di + 1),
+				   name_len);
 
+		d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
+		btrfs_dir_item_key_to_cpu(leaf, di, &location);
 
-			/* is this a reference to our own snapshot? If so
-			 * skip it.
-			 *
-			 * In contrast to old kernels, we insert the snapshot's
-			 * dir item and dir index after it has been created, so
-			 * we won't find a reference to our own snapshot. We
-			 * still keep the following code for backward
-			 * compatibility.
-			 */
-			if (location.type == BTRFS_ROOT_ITEM_KEY &&
-			    location.objectid == root->root_key.objectid) {
-				over = 0;
-				goto skip;
-			}
-			over = !dir_emit(ctx, name_ptr, name_len,
-				       location.objectid, d_type);
+		over = !dir_emit(ctx, name_ptr, name_len, location.objectid,
+				 d_type);
 
-skip:
-			if (name_ptr != tmp_name)
-				kfree(name_ptr);
+		if (name_ptr != tmp_name)
+			kfree(name_ptr);
 
-			if (over)
-				goto nopos;
 			emitted = true;
-			di_len = btrfs_dir_name_len(leaf, di) +
-				 btrfs_dir_data_len(leaf, di) + sizeof(*di);
-			di_cur += di_len;
-			di = (struct btrfs_dir_item *)((char *)di + di_len);
-		}
+		if (over)
+			goto nopos;
 next:
 		path->slots[0]++;
 	}
 
-	if (key_type == BTRFS_DIR_INDEX_KEY) {
-		if (is_curr)
-			ctx->pos++;
-		ret = btrfs_readdir_delayed_dir_index(ctx, &ins_list, &emitted);
-		if (ret)
-			goto nopos;
-	}
+	if (is_curr)
+		ctx->pos++;
+	ret = btrfs_readdir_delayed_dir_index(ctx, &ins_list, &emitted);
+	if (ret)
+		goto nopos;
 
 	/*
 	 * If we haven't emitted any dir entry, we must not touch ctx->pos as
@@ -5970,12 +5929,10 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 	 * last entry requires it because doing so has broken 32bit apps
 	 * in the past.
 	 */
-	if (key_type == BTRFS_DIR_INDEX_KEY) {
-		if (ctx->pos >= INT_MAX)
-			ctx->pos = LLONG_MAX;
-		else
-			ctx->pos = INT_MAX;
-	}
+	if (ctx->pos >= INT_MAX)
+		ctx->pos = LLONG_MAX;
+	else
+		ctx->pos = INT_MAX;
 nopos:
 	ret = 0;
 err: