bcachefs: Lookup/create lost+found lazily

This is prep work for subvolumes - each subvolume will have its own
lost+found.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fsck.c

@@ -38,7 +38,7 @@ static s64 bch2_count_inode_sectors(struct btree_trans *trans, u64 inum)
 	return ret ?: sectors;
 }
 
-static int lookup_inode(struct btree_trans *trans, u64 inode_nr,
+static int __lookup_inode(struct btree_trans *trans, u64 inode_nr,
 			  struct bch_inode_unpacked *inode,
 			  u32 *snapshot)
 {
@@ -63,7 +63,14 @@ static int lookup_inode(struct btree_trans *trans, u64 inode_nr,
 	return ret;
 }
 
-static int write_inode(struct btree_trans *trans,
+static int lookup_inode(struct btree_trans *trans, u64 inode_nr,
+			struct bch_inode_unpacked *inode,
+			u32 *snapshot)
+{
+	return lockrestart_do(trans, __lookup_inode(trans, inode_nr, inode, snapshot));
+}
+
+static int __write_inode(struct btree_trans *trans,
 			 struct bch_inode_unpacked *inode,
 			 u32 snapshot)
 {
@@ -71,11 +78,19 @@ static int write_inode(struct btree_trans *trans,
 		bch2_trans_get_iter(trans, BTREE_ID_inodes,
 				    SPOS(0, inode->bi_inum, snapshot),
 				    BTREE_ITER_INTENT);
+	int ret = bch2_inode_write(trans, inode_iter, inode);
+	bch2_trans_iter_put(trans, inode_iter);
+	return ret;
+}
+
+static int write_inode(struct btree_trans *trans,
+		       struct bch_inode_unpacked *inode,
+		       u32 snapshot)
+{
 	int ret = __bch2_trans_do(trans, NULL, NULL,
 				  BTREE_INSERT_NOFAIL|
 				  BTREE_INSERT_LAZY_RW,
-				  bch2_inode_write(trans, inode_iter, inode));
-	bch2_trans_iter_put(trans, inode_iter);
+				  __write_inode(trans, inode, snapshot));
 	if (ret)
 		bch_err(trans->c, "error in fsck: error %i updating inode", ret);
 	return ret;
@@ -114,57 +129,101 @@ static int remove_dirent(struct btree_trans *trans, struct bpos pos)
 	return ret;
 }
 
-static int __reattach_inode(struct btree_trans *trans,
-			    struct bch_inode_unpacked *lostfound,
-			    u64 inum)
+/* Get lost+found, create if it doesn't exist: */
+static int lookup_lostfound(struct btree_trans *trans,
+			    struct bch_inode_unpacked *lostfound)
 {
-	struct bch_hash_info dir_hash =
-		bch2_hash_info_init(trans->c, lostfound);
-	struct bch_inode_unpacked inode_u;
-	char name_buf[20];
-	struct qstr name;
-	u64 dir_offset = 0;
+	struct bch_fs *c = trans->c;
+	struct bch_inode_unpacked root;
+	struct bch_hash_info root_hash_info;
+	struct qstr lostfound_str = QSTR("lost+found");
+	u64 inum;
 	u32 snapshot;
 	int ret;
 
-	snprintf(name_buf, sizeof(name_buf), "%llu", inum);
-	name = (struct qstr) QSTR(name_buf);
-
-	ret = lookup_inode(trans, inum, &inode_u, &snapshot);
-	if (ret)
+	ret = lookup_inode(trans, BCACHEFS_ROOT_INO, &root, &snapshot);
+	if (ret && ret != -ENOENT)
 		return ret;
 
-	if (S_ISDIR(inode_u.bi_mode)) {
-		lostfound->bi_nlink++;
+	root_hash_info = bch2_hash_info_init(c, &root);
+	inum = bch2_dirent_lookup(c, BCACHEFS_ROOT_INO, &root_hash_info,
+				  &lostfound_str);
+	if (!inum) {
+		bch_notice(c, "creating lost+found");
+		goto create_lostfound;
+	}
 
-		ret = write_inode(trans, lostfound, U32_MAX);
-		if (ret)
+	ret = lookup_inode(trans, inum, lostfound, &snapshot);
+	if (ret && ret != -ENOENT) {
+		/*
+		 * The check_dirents pass has already run, dangling dirents
+		 * shouldn't exist here:
+		 */
+		bch_err(c, "error looking up lost+found: %i", ret);
 		return ret;
 	}
 
-	ret = bch2_dirent_create(trans, lostfound->bi_inum, &dir_hash,
-				 mode_to_type(inode_u.bi_mode),
-				 &name, inum, &dir_offset,
-				 BCH_HASH_SET_MUST_CREATE);
-	if (ret)
-		return ret;
+	if (ret == -ENOENT) {
+create_lostfound:
+		bch2_inode_init_early(c, lostfound);
 
-	inode_u.bi_dir		= lostfound->bi_inum;
-	inode_u.bi_dir_offset	= dir_offset;
+		ret = __bch2_trans_do(trans, NULL, NULL,
+				      BTREE_INSERT_NOFAIL|
+				      BTREE_INSERT_LAZY_RW,
+			bch2_create_trans(trans,
+					  BCACHEFS_ROOT_INO, &root,
+					  lostfound,
+					  &lostfound_str,
+					  0, 0, S_IFDIR|0700, 0, NULL, NULL));
+		if (ret)
+			bch_err(c, "error creating lost+found: %i", ret);
+	}
 
-	return write_inode(trans, &inode_u, U32_MAX);
+	return 0;
 }
 
 static int reattach_inode(struct btree_trans *trans,
-			  struct bch_inode_unpacked *lostfound,
-			  u64 inum)
+			  struct bch_inode_unpacked *inode)
 {
-	int ret = __bch2_trans_do(trans, NULL, NULL, BTREE_INSERT_LAZY_RW,
-			      __reattach_inode(trans, lostfound, inum));
+	struct bch_hash_info dir_hash;
+	struct bch_inode_unpacked lostfound;
+	char name_buf[20];
+	struct qstr name;
+	u64 dir_offset = 0;
+	int ret;
+
+	ret = lookup_lostfound(trans, &lostfound);
 	if (ret)
-		bch_err(trans->c, "error %i reattaching inode %llu", ret, inum);
+		return ret;
 
+	if (S_ISDIR(inode->bi_mode)) {
+		lostfound.bi_nlink++;
+
+		ret = write_inode(trans, &lostfound, U32_MAX);
+		if (ret)
 			return ret;
+	}
+
+	dir_hash = bch2_hash_info_init(trans->c, &lostfound);
+
+	snprintf(name_buf, sizeof(name_buf), "%llu", inode->bi_inum);
+	name = (struct qstr) QSTR(name_buf);
+
+	ret = __bch2_trans_do(trans, NULL, NULL, BTREE_INSERT_LAZY_RW,
+		bch2_dirent_create(trans, lostfound.bi_inum, &dir_hash,
+				   mode_to_type(inode->bi_mode),
+				   &name, inode->bi_inum, &dir_offset,
+				   BCH_HASH_SET_MUST_CREATE));
+	if (ret) {
+		bch_err(trans->c, "error %i reattaching inode %llu",
+			ret, inode->bi_inum);
+		return ret;
+	}
+
+	inode->bi_dir		= lostfound.bi_inum;
+	inode->bi_dir_offset	= dir_offset;
+
+	return write_inode(trans, inode, U32_MAX);
 }
 
 static int remove_backpointer(struct btree_trans *trans,
@@ -931,58 +990,6 @@ static int check_root(struct bch_fs *c, struct bch_inode_unpacked *root_inode)
 				 BTREE_INSERT_LAZY_RW);
 }
 
-/* Get lost+found, create if it doesn't exist: */
-static int check_lostfound(struct bch_fs *c,
-			   struct bch_inode_unpacked *root_inode,
-			   struct bch_inode_unpacked *lostfound_inode)
-{
-	struct qstr lostfound = QSTR("lost+found");
-	struct bch_hash_info root_hash_info =
-		bch2_hash_info_init(c, root_inode);
-	u64 inum;
-	u32 snapshot;
-	int ret;
-
-	bch_verbose(c, "checking lost+found");
-
-	inum = bch2_dirent_lookup(c, BCACHEFS_ROOT_INO, &root_hash_info,
-				 &lostfound);
-	if (!inum) {
-		bch_notice(c, "creating lost+found");
-		goto create_lostfound;
-	}
-
-	ret = bch2_trans_do(c, NULL, NULL, 0,
-		lookup_inode(&trans, inum, lostfound_inode, &snapshot));
-	if (ret && ret != -ENOENT)
-		return ret;
-
-	if (fsck_err_on(ret, c, "lost+found missing"))
-		goto create_lostfound;
-
-	if (fsck_err_on(!S_ISDIR(lostfound_inode->bi_mode), c,
-			"lost+found inode not a directory"))
-		goto create_lostfound;
-
-	return 0;
-fsck_err:
-	return ret;
-create_lostfound:
-	bch2_inode_init_early(c, lostfound_inode);
-
-	ret = bch2_trans_do(c, NULL, NULL,
-			    BTREE_INSERT_NOFAIL|
-			    BTREE_INSERT_LAZY_RW,
-		bch2_create_trans(&trans,
-				  BCACHEFS_ROOT_INO, root_inode,
-				  lostfound_inode, &lostfound,
-				  0, 0, S_IFDIR|0700, 0, NULL, NULL));
-	if (ret)
-		bch_err(c, "error creating lost+found: %i", ret);
-
-	return ret;
-}
-
 struct pathbuf {
 	size_t		nr;
 	size_t		size;
@@ -1014,7 +1021,6 @@ static int path_down(struct pathbuf *p, u64 inum)
 }
 
 static int check_path(struct btree_trans *trans,
-		      struct bch_inode_unpacked *lostfound,
 		      struct pathbuf *p,
 		      struct bch_inode_unpacked *inode)
 {
@@ -1038,7 +1044,7 @@ static int check_path(struct btree_trans *trans,
 				     inode->bi_nlink,
 				     inode->bi_dir,
 				     inode->bi_dir_offset))
-				ret = reattach_inode(trans, lostfound, inode->bi_inum);
+				ret = reattach_inode(trans, inode);
 			break;
 		}
 		ret = 0;
@@ -1067,12 +1073,11 @@ static int check_path(struct btree_trans *trans,
 				break;
 			}
 
-			ret = reattach_inode(trans, lostfound, inode->bi_inum);
+			ret = reattach_inode(trans, inode);
 			break;
 		}
 
-		ret = lockrestart_do(trans,
-				lookup_inode(trans, inode->bi_dir, inode, &snapshot));
+		ret = lookup_inode(trans, inode->bi_dir, inode, &snapshot);
 		if (ret) {
 			/* Should have been caught in dirents pass */
 			bch_err(c, "error looking up parent directory: %i", ret);
@@ -1090,8 +1095,7 @@ static int check_path(struct btree_trans *trans,
  * After check_dirents(), if an inode backpointer doesn't exist that means it's
  * unreachable:
  */
-static int check_directory_structure(struct bch_fs *c,
-				     struct bch_inode_unpacked *lostfound)
+static int check_directory_structure(struct bch_fs *c)
 {
 	struct btree_trans trans;
 	struct btree_iter *iter;
@@ -1113,7 +1117,7 @@ static int check_directory_structure(struct bch_fs *c,
 			break;
 		}
 
-		ret = check_path(&trans, lostfound, &path, &u);
+		ret = check_path(&trans, &path, &u);
 		if (ret)
 			break;
 	}
@@ -1190,7 +1194,6 @@ static int bch2_gc_walk_dirents(struct bch_fs *c, nlink_table *links,
 }
 
 static int check_inode_nlink(struct btree_trans *trans,
-			     struct bch_inode_unpacked *lostfound_inode,
 			     struct btree_iter *iter,
 			     struct bkey_s_c_inode inode,
 			     unsigned nlink)
@@ -1238,7 +1241,6 @@ static int check_inode_nlink(struct btree_trans *trans,
 
 noinline_for_stack
 static int bch2_gc_walk_inodes(struct bch_fs *c,
-			       struct bch_inode_unpacked *lostfound_inode,
 			       nlink_table *links,
 			       u64 range_start, u64 range_end)
 {
@@ -1259,7 +1261,7 @@ static int bch2_gc_walk_inodes(struct bch_fs *c,
 			continue;
 
 		link = genradix_ptr(links, k.k->p.offset - range_start);
-		ret = check_inode_nlink(&trans, lostfound_inode, iter,
+		ret = check_inode_nlink(&trans, iter,
 					bkey_s_c_to_inode(k), link ? link->count : 0);
 		if (ret)
 			break;
@@ -1275,8 +1277,7 @@ static int bch2_gc_walk_inodes(struct bch_fs *c,
 }
 
 noinline_for_stack
-static int check_nlinks(struct bch_fs *c,
-			      struct bch_inode_unpacked *lostfound_inode)
+static int check_nlinks(struct bch_fs *c)
 {
 	nlink_table links;
 	u64 this_iter_range_start, next_iter_range_start = 0;
@@ -1296,7 +1297,7 @@ static int check_nlinks(struct bch_fs *c,
 		if (ret)
 			break;
 
-		ret = bch2_gc_walk_inodes(c, lostfound_inode, &links,
+		ret = bch2_gc_walk_inodes(c, &links,
 					 this_iter_range_start,
 					 next_iter_range_start);
 		if (ret)
@@ -1316,16 +1317,15 @@ static int check_nlinks(struct bch_fs *c,
  */
 int bch2_fsck_full(struct bch_fs *c)
 {
-	struct bch_inode_unpacked root_inode, lostfound_inode;
+	struct bch_inode_unpacked root_inode;
 
 	return  check_inodes(c, true) ?:
 		check_extents(c) ?:
 		check_dirents(c) ?:
 		check_xattrs(c) ?:
 		check_root(c, &root_inode) ?:
-		check_lostfound(c, &root_inode, &lostfound_inode) ?:
-		check_directory_structure(c, &lostfound_inode) ?:
-		check_nlinks(c, &lostfound_inode);
+		check_directory_structure(c) ?:
+		check_nlinks(c);
 }
 
 int bch2_fsck_walk_inodes_only(struct bch_fs *c)