btrfs-progs: check: report deprecated inode cache as errors

check/main.c

@@ -86,6 +86,7 @@ bool no_holes = false;
 bool is_free_space_tree = false;
 bool init_extent_tree = false;
 bool check_data_csum = false;
+static bool found_free_ino_cache = false;
 struct cache_tree *roots_info_cache = NULL;
 
 enum btrfs_check_mode {
@@ -606,6 +607,8 @@ static void print_inode_error(struct btrfs_root *root, struct inode_record *rec)
 	fprintf(stderr, "root %llu inode %llu errors %x",
 		root_objectid, rec->ino, rec->errors);
 
+	if (errors & I_ERR_DEPRECATED_FREE_INO)
+		fprintf(stderr, ", deprecated free inode cache");
 	if (errors & I_ERR_NO_INODE_ITEM)
 		fprintf(stderr, ", no inode item");
 	if (errors & I_ERR_NO_ORPHAN_ITEM)
@@ -773,9 +776,6 @@ static struct inode_record *get_inode_rec(struct cache_tree *inode_cache,
 		node->cache.size = 1;
 		node->data = rec;
 
-		if (ino == BTRFS_FREE_INO_OBJECTID)
-			rec->found_link = 1;
-
 		ret = insert_cache_extent(inode_cache, &node->cache);
 		if (ret) {
 			free(rec);
@@ -3224,6 +3224,10 @@ static int check_inode_recs(struct btrfs_root *root,
 			}
 		}
 
+		if (rec->ino == BTRFS_FREE_INO_OBJECTID) {
+			rec->errors |= I_ERR_DEPRECATED_FREE_INO;
+			found_free_ino_cache = true;
+		}
 		if (!rec->found_inode_item)
 			rec->errors |= I_ERR_NO_INODE_ITEM;
 		if (rec->found_link != rec->nlink)
@@ -10834,6 +10838,9 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 
 	ret = do_check_fs_roots(&root_cache);
 	task_stop(g_task_ctx.info);
+	if (found_free_ino_cache)
+		pr_verbose(LOG_DEFAULT,
+			   "deprecated inode cache can be removed by 'btrfs rescue clear-ino-cache'\n");
 	err |= !!ret;
 	if (ret) {
 		error("errors found in fs roots");

check/mode-lowmem.c

@@ -44,6 +44,7 @@
 
 static u64 last_allocated_chunk;
 static u64 total_used = 0;
+static bool found_free_ino_cache = false;
 
 static int calc_extent_flag(struct btrfs_root *root, struct extent_buffer *eb,
 			    u64 *flags_ret)
@@ -2629,6 +2630,12 @@ static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path)
 		return err;
 	}
 
+	if (inode_id == BTRFS_FREE_INO_OBJECTID) {
+		warning("subvolume %lld has deprecated inode cache",
+			root->root_key.objectid);
+		found_free_ino_cache = true;
+	}
+
 	is_orphan = has_orphan_item(root, inode_id);
 	ii = btrfs_item_ptr(node, slot, struct btrfs_inode_item);
 	isize = btrfs_inode_size(node, ii);
@@ -5616,6 +5623,9 @@ int check_fs_roots_lowmem(void)
 
 out:
 	btrfs_release_path(&path);
+	if (found_free_ino_cache)
+		pr_verbose(LOG_DEFAULT,
+			   "deprecated inode cache can be removed by 'btrfs rescue clear-ino-cache'\n");
 	return err;
 }
 

check/mode-original.h

@@ -189,6 +189,7 @@ struct unaligned_extent_rec_t {
 #define I_ERR_INVALID_GEN		(1U << 20)
 #define I_ERR_INVALID_NLINK		(1U << 21)
 #define I_ERR_INVALID_XATTR		(1U << 22)
+#define I_ERR_DEPRECATED_FREE_INO	(1U << 23)
 
 struct inode_record {
 	struct list_head backrefs;

tests/fsck-tests/064-deprecated-inode-cache/test.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+#
+# Verify that check can report deprecated inode cache as an error
+
+source "$TEST_TOP/common" || exit
+
+check_prereq btrfs
+
+check_image() {
+	run_mustfail "deprecated inode cache not reported as an error" \
+		"$TOP/btrfs" check "$1"
+}
+
+check_all_images