[PATCH v3 1/2] erofs-utils: lib: add API to iterate dirs in EROFS

[PATCH v3 1/2] erofs-utils: lib: add API to iterate dirs in EROFS

[Gao Xiang]

From: Gao Xiang <hsiangkao@linux.alibaba.com>

This introduces erofs_iterate_dir() to iterate all dirents in
a directory inode and convert erofsfuse to use the API.

Note that it doesn't recursively walk into sub-directories.
If it's really needed, users should handle this in the callback.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
v3: https://lore.kernel.org/linux-erofs/20211215194200.61210-1-hsiangkao@linux.alibaba.com/
changes since v2:
 - resolve nid endianless issue.

 fuse/Makefile.am         |   2 +-
 fuse/dir.c               | 100 -----------------------
 fuse/main.c              |  52 +++++++++++-
 include/erofs/dir.h      |  53 +++++++++++++
 include/erofs/internal.h |   8 ++
 lib/Makefile.am          |   2 +-
 lib/dir.c                | 167 +++++++++++++++++++++++++++++++++++++++
 7 files changed, 280 insertions(+), 104 deletions(-)
 delete mode 100644 fuse/dir.c
 create mode 100644 include/erofs/dir.h
 create mode 100644 lib/dir.c

diff --git a/fuse/Makefile.am b/fuse/Makefile.am
index 8a2d4720d1b7..5aa5ac07be70 100644
--- a/fuse/Makefile.am
+++ b/fuse/Makefile.am
@@ -3,7 +3,7 @@
 AUTOMAKE_OPTIONS = foreign
 noinst_HEADERS = $(top_srcdir)/fuse/macosx.h
 bin_PROGRAMS     = erofsfuse
-erofsfuse_SOURCES = dir.c main.c
+erofsfuse_SOURCES = main.c
 erofsfuse_CFLAGS = -Wall -Werror -I$(top_srcdir)/include
 erofsfuse_CFLAGS += -DFUSE_USE_VERSION=26 ${libfuse_CFLAGS} ${libselinux_CFLAGS}
 erofsfuse_LDADD = $(top_builddir)/lib/liberofs.la ${libfuse_LIBS} ${liblz4_LIBS} \
diff --git a/fuse/dir.c b/fuse/dir.c
deleted file mode 100644
index bc8735bedb6f..000000000000
--- a/fuse/dir.c
+++ /dev/null
@@ -1,100 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Created by Li Guifu <blucerlee@gmail.com>
- */
-#include <fuse.h>
-#include <fuse_opt.h>
-#include "macosx.h"
-#include "erofs/internal.h"
-#include "erofs/print.h"
-
-static int erofs_fill_dentries(struct erofs_inode *dir,
-			       fuse_fill_dir_t filler, void *buf,
-			       void *dblk, unsigned int nameoff,
-			       unsigned int maxsize)
-{
-	struct erofs_dirent *de = dblk;
-	const struct erofs_dirent *end = dblk + nameoff;
-	char namebuf[EROFS_NAME_LEN + 1];
-
-	while (de < end) {
-		const char *de_name;
-		unsigned int de_namelen;
-
-		nameoff = le16_to_cpu(de->nameoff);
-		de_name = (char *)dblk + nameoff;
-
-		/* the last dirent in the block? */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
-			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
-
-		/* a corrupted entry is found */
-		if (nameoff + de_namelen > maxsize ||
-		    de_namelen > EROFS_NAME_LEN) {
-			erofs_err("bogus dirent @ nid %llu", dir->nid | 0ULL);
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
-
-		memcpy(namebuf, de_name, de_namelen);
-		namebuf[de_namelen] = '\0';
-
-		filler(buf, namebuf, NULL, 0);
-		++de;
-	}
-	return 0;
-}
-
-int erofsfuse_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
-		      off_t offset, struct fuse_file_info *fi)
-{
-	int ret;
-	struct erofs_inode dir;
-	char dblk[EROFS_BLKSIZ];
-	erofs_off_t pos;
-
-	erofs_dbg("readdir:%s offset=%llu", path, (long long)offset);
-
-	ret = erofs_ilookup(path, &dir);
-	if (ret)
-		return ret;
-
-	erofs_dbg("path=%s nid = %llu", path, dir.nid | 0ULL);
-
-	if (!S_ISDIR(dir.i_mode))
-		return -ENOTDIR;
-
-	if (!dir.i_size)
-		return 0;
-
-	pos = 0;
-	while (pos < dir.i_size) {
-		unsigned int nameoff, maxsize;
-		struct erofs_dirent *de;
-
-		maxsize = min_t(unsigned int, EROFS_BLKSIZ,
-				dir.i_size - pos);
-		ret = erofs_pread(&dir, dblk, maxsize, pos);
-		if (ret)
-			return ret;
-
-		de = (struct erofs_dirent *)dblk;
-		nameoff = le16_to_cpu(de->nameoff);
-		if (nameoff < sizeof(struct erofs_dirent) ||
-		    nameoff >= PAGE_SIZE) {
-			erofs_err("invalid de[0].nameoff %u @ nid %llu",
-				  nameoff, dir.nid | 0ULL);
-			ret = -EFSCORRUPTED;
-			break;
-		}
-
-		ret = erofs_fill_dentries(&dir, filler, buf,
-					  dblk, nameoff, maxsize);
-		if (ret)
-			break;
-		pos += maxsize;
-	}
-	return 0;
-}
diff --git a/fuse/main.c b/fuse/main.c
index 255965e30969..2549d8a9b33a 100644
--- a/fuse/main.c
+++ b/fuse/main.c
@@ -12,9 +12,57 @@
 #include "erofs/config.h"
 #include "erofs/print.h"
 #include "erofs/io.h"
+#include "erofs/dir.h"
 
-int erofsfuse_readdir(const char *path, void *buffer, fuse_fill_dir_t filler,
-		      off_t offset, struct fuse_file_info *fi);
+struct erofsfuse_dir_context {
+	struct erofs_dir_context ctx;
+	fuse_fill_dir_t filler;
+	struct fuse_file_info *fi;
+	void *buf;
+};
+
+static int erofsfuse_fill_dentries(struct erofs_dir_context *ctx)
+{
+	struct erofsfuse_dir_context *fusectx = (void *)ctx;
+	char dname[EROFS_NAME_LEN + 1];
+
+	strncpy(dname, ctx->dname, ctx->de_namelen);
+	dname[ctx->de_namelen] = '\0';
+	fusectx->filler(fusectx->buf, dname, NULL, 0);
+	return 0;
+}
+
+int erofsfuse_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
+		      off_t offset, struct fuse_file_info *fi)
+{
+	int ret;
+	struct erofs_inode dir;
+	struct erofsfuse_dir_context ctx = {
+		.ctx.dir = &dir,
+		.ctx.cb = erofsfuse_fill_dentries,
+		.filler = filler,
+		.fi = fi,
+		.buf = buf,
+	};
+	erofs_dbg("readdir:%s offset=%llu", path, (long long)offset);
+
+	ret = erofs_ilookup(path, &dir);
+	if (ret)
+		return ret;
+
+	erofs_dbg("path=%s nid = %llu", path, dir.nid | 0ULL);
+	if (!S_ISDIR(dir.i_mode))
+		return -ENOTDIR;
+
+	if (!dir.i_size)
+		return 0;
+#ifdef NDEBUG
+	return erofs_iterate_dir(&ctx.ctx, false);
+#else
+	return erofs_iterate_dir(&ctx.ctx, true);
+#endif
+
+}
 
 static void *erofsfuse_init(struct fuse_conn_info *info)
 {
diff --git a/include/erofs/dir.h b/include/erofs/dir.h
new file mode 100644
index 000000000000..25d6ce7ca072
--- /dev/null
+++ b/include/erofs/dir.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0 */
+#ifndef __EROFS_DIR_H
+#define __EROFS_DIR_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include "internal.h"
+
+#define EROFS_READDIR_VALID_PNID	0x0001
+#define EROFS_READDIR_DOTDOT_FOUND	0x0002
+#define EROFS_READDIR_DOT_FOUND		0x0004
+
+#define EROFS_READDIR_ALL_SPECIAL_FOUND	\
+	(EROFS_READDIR_DOTDOT_FOUND | EROFS_READDIR_DOT_FOUND)
+
+struct erofs_dir_context;
+
+/* callback function for iterating over inodes of EROFS */
+typedef int (*erofs_readdir_cb)(struct erofs_dir_context *);
+
+/*
+ * Callers could use a wrapper to contain extra information.
+ *
+ * Note that callback can reuse `struct erofs_dir_context' with care
+ * to avoid stack overflow due to deep recursion: dir, pnid, flags,
+ * (optional)cb SHOULD be saved to ensure the original state.
+ *
+ * Another way is to allocate `struct erofs_dir_context' on heap,
+ * and chain them together for multi-level traversal.
+ */
+struct erofs_dir_context {
+	struct erofs_inode *dir;
+	erofs_readdir_cb cb;
+	erofs_nid_t pnid;		/* optional */
+
+	/* [out] the dirent which is under processing */
+	const char *dname;
+	erofs_nid_t de_nid;
+	u8 de_namelen, de_ftype, flags;
+	bool dot_dotdot;
+};
+
+/* iterate over inodes that are in directory */
+int erofs_iterate_dir(struct erofs_dir_context *ctx, bool fsck);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index e6beb8cb8528..d2adf57d8ae2 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -235,6 +235,14 @@ struct erofs_dentry {
 	};
 };
 
+static inline bool is_dot_dotdot_len(const char *name, unsigned int len)
+{
+	if (len >= 1 && name[0] != '.')
+		return false;
+
+	return len == 1 || (len == 2 && name[1] == '.');
+}
+
 static inline bool is_dot_dotdot(const char *name)
 {
 	if (name[0] != '.')
diff --git a/lib/Makefile.am b/lib/Makefile.am
index c745e493c391..4a2501342729 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -27,7 +27,7 @@ noinst_HEADERS = $(top_srcdir)/include/erofs_fs.h \
 noinst_HEADERS += compressor.h
 liberofs_la_SOURCES = config.c io.c cache.c super.c inode.c xattr.c exclude.c \
 		      namei.c data.c compress.c compressor.c zmap.c decompress.c \
-		      compress_hints.c hashmap.c sha256.c blobchunk.c
+		      compress_hints.c hashmap.c sha256.c blobchunk.c dir.c
 liberofs_la_CFLAGS = -Wall -Werror -I$(top_srcdir)/include
 if ENABLE_LZ4
 liberofs_la_CFLAGS += ${LZ4_CFLAGS}
diff --git a/lib/dir.c b/lib/dir.c
new file mode 100644
index 000000000000..63e35ba2318b
--- /dev/null
+++ b/lib/dir.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
+#include "erofs/print.h"
+#include "erofs/dir.h"
+#include <stdlib.h>
+
+static int traverse_dirents(struct erofs_dir_context *ctx,
+			    void *dentry_blk, unsigned int lblk,
+			    unsigned int next_nameoff, unsigned int maxsize,
+			    bool fsck)
+{
+	struct erofs_dirent *de = dentry_blk;
+	const struct erofs_dirent *end = dentry_blk + next_nameoff;
+	const char *prev_name = NULL;
+	const char *errmsg;
+	unsigned int prev_namelen = 0;
+	int ret = 0;
+	bool silent = false;
+
+	while (de < end) {
+		const char *de_name;
+		unsigned int de_namelen;
+		unsigned int nameoff;
+
+		nameoff = le16_to_cpu(de->nameoff);
+		de_name = (char *)dentry_blk + nameoff;
+
+		/* the last dirent check */
+		if (de + 1 >= end)
+			de_namelen = strnlen(de_name, maxsize - nameoff);
+		else
+			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
+
+		ctx->de_nid = le64_to_cpu(de->nid);
+		erofs_dbg("traversed nid (%llu)", ctx->de_nid | 0ULL);
+
+		ret = -EFSCORRUPTED;
+		/* corrupted entry check */
+		if (nameoff != next_nameoff) {
+			errmsg = "bogus dirent nameoff";
+			break;
+		}
+
+		if (nameoff + de_namelen > maxsize ||
+				de_namelen > EROFS_NAME_LEN) {
+			errmsg = "bogus dirent namelen";
+			break;
+		}
+
+		if (fsck && prev_name) {
+			int cmp = strncmp(prev_name, de_name,
+					  min(prev_namelen, de_namelen));
+
+			if (cmp > 0 || (cmp == 0 &&
+					prev_namelen >= de_namelen)) {
+				errmsg = "wrong dirent name order";
+				break;
+			}
+		}
+
+		if (fsck && de->file_type >= EROFS_FT_MAX) {
+			errmsg = "invalid file type %u";
+			break;
+		}
+
+		ctx->dname = de_name;
+		ctx->de_namelen = de_namelen;
+		ctx->dot_dotdot = is_dot_dotdot_len(de_name, de_namelen);
+		if (ctx->dot_dotdot) {
+			switch (de_namelen) {
+			case 2:
+				if (fsck &&
+				    (ctx->flags & EROFS_READDIR_DOTDOT_FOUND)) {
+					errmsg = "duplicated `..' dirent";
+					goto out;
+				}
+				ctx->flags |= EROFS_READDIR_DOTDOT_FOUND;
+				if (sbi.root_nid == ctx->dir->nid) {
+					ctx->pnid = sbi.root_nid;
+					ctx->flags |= EROFS_READDIR_VALID_PNID;
+				}
+				if (fsck &&
+				    (ctx->flags & EROFS_READDIR_VALID_PNID) &&
+				    ctx->de_nid != ctx->pnid) {
+					errmsg = "corrupted `..' dirent";
+					goto out;
+				}
+				break;
+			case 1:
+				if (fsck &&
+				    (ctx->flags & EROFS_READDIR_DOT_FOUND)) {
+					errmsg = "duplicated `.' dirent";
+					goto out;
+				}
+
+				ctx->flags |= EROFS_READDIR_DOT_FOUND;
+				if (fsck && ctx->de_nid != ctx->dir->nid) {
+					errmsg = "corrupted `.' dirent";
+					goto out;
+				}
+				break;
+			}
+		}
+		ret = ctx->cb(ctx);
+		if (ret) {
+			silent = true;
+			break;
+		}
+		prev_name = de_name;
+		prev_namelen = de_namelen;
+		next_nameoff += de_namelen;
+		++de;
+	}
+out:
+	if (ret && !silent)
+		erofs_err("%s @ nid %llu, lblk %u, index %lu",
+			  errmsg, ctx->dir->nid | 0ULL, lblk,
+			  (de - (struct erofs_dirent *)dentry_blk) | 0UL);
+	return ret;
+}
+
+int erofs_iterate_dir(struct erofs_dir_context *ctx, bool fsck)
+{
+	struct erofs_inode *dir = ctx->dir;
+	int err;
+	erofs_off_t pos;
+	char buf[EROFS_BLKSIZ];
+
+	if ((dir->i_mode & S_IFMT) != S_IFDIR)
+		return -ENOTDIR;
+
+	ctx->flags &= ~EROFS_READDIR_ALL_SPECIAL_FOUND;
+	pos = 0;
+	while (pos < dir->i_size) {
+		erofs_blk_t lblk = erofs_blknr(pos);
+		erofs_off_t maxsize = min_t(erofs_off_t,
+					dir->i_size - pos, EROFS_BLKSIZ);
+		const struct erofs_dirent *de = (const void *)buf;
+		unsigned int nameoff;
+
+		err = erofs_pread(dir, buf, maxsize, pos);
+		if (err) {
+			erofs_err("I/O error occurred when reading dirents @ nid %llu, lblk %u: %d",
+				  dir->nid | 0ULL, lblk, err);
+			return err;
+		}
+
+		nameoff = le16_to_cpu(de->nameoff);
+		if (nameoff < sizeof(struct erofs_dirent) ||
+		    nameoff >= PAGE_SIZE) {
+			erofs_err("invalid de[0].nameoff %u @ nid %llu, lblk %u",
+				  nameoff, dir->nid | 0ULL, lblk);
+			return -EFSCORRUPTED;
+		}
+		err = traverse_dirents(ctx, buf, lblk, nameoff, maxsize, fsck);
+		if (err)
+			break;
+		pos += maxsize;
+	}
+
+	if (fsck && (ctx->flags & EROFS_READDIR_ALL_SPECIAL_FOUND) !=
+			EROFS_READDIR_ALL_SPECIAL_FOUND) {
+		erofs_err("`.' or `..' dirent is missing @ nid %llu",
+			  dir->nid | 0ULL);
+		return -EFSCORRUPTED;
+	}
+	return 0;
+}
-- 
2.20.1

[PATCH v3 2/2] erofs-utils: fsck: convert to use erofs_iterate_dir()

[Gao Xiang]

From: Gao Xiang <hsiangkao@linux.alibaba.com>

No need to open code after erofs_iterate_dir() is finalized in
liberofs.

However, there are still some TODOs for fsck:
 - Avoid too deep recursive traversal, sceptically forming a loop;
 - Check link counts at runtime to keep consistency;
 - Check if any ftype / i_mode mismatches.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fsck/main.c | 178 +++++++---------------------------------------------
 1 file changed, 23 insertions(+), 155 deletions(-)

diff --git a/fsck/main.c b/fsck/main.c
index ad48e35f587b..038f43badb8f 100644
--- a/fsck/main.c
+++ b/fsck/main.c
@@ -10,8 +10,9 @@
 #include "erofs/print.h"
 #include "erofs/io.h"
 #include "erofs/decompress.h"
+#include "erofs/dir.h"
 
-static void erofs_check_inode(erofs_nid_t pnid, erofs_nid_t nid);
+static int erofsfsck_check_inode(erofs_nid_t pnid, erofs_nid_t nid);
 
 struct erofsfsck_cfg {
 	bool corrupted;
@@ -126,121 +127,6 @@ static int erofs_check_sb_chksum(void)
 	return 0;
 }
 
-static bool check_special_dentry(struct erofs_dirent *de,
-				 unsigned int de_namelen, erofs_nid_t nid,
-				 erofs_nid_t pnid)
-{
-	if (de_namelen == 2 && de->nid != pnid) {
-		erofs_err("wrong parent dir nid(%llu): pnid(%llu) @ nid(%llu)",
-			  de->nid | 0ULL, pnid | 0ULL, nid | 0ULL);
-		return false;
-	}
-
-	if (de_namelen == 1 && de->nid != nid) {
-		erofs_err("wrong current dir nid(%llu) @ nid(%llu)",
-			  de->nid | 0ULL, nid | 0ULL);
-		return false;
-	}
-	return true;
-}
-
-static int traverse_dirents(erofs_nid_t pnid, erofs_nid_t nid,
-			    void *dentry_blk, erofs_blk_t block,
-			    unsigned int next_nameoff, unsigned int maxsize)
-{
-	struct erofs_dirent *de = dentry_blk;
-	const struct erofs_dirent *end = dentry_blk + next_nameoff;
-	unsigned int idx = 0;
-	char *prev_name = NULL, *cur_name = NULL;
-	int ret = 0;
-
-	erofs_dbg("traversing pnid(%llu), nid(%llu)", pnid | 0ULL, nid | 0ULL);
-
-	if (!block && (next_nameoff < 2 * sizeof(struct erofs_dirent))) {
-		erofs_err("too small dirents of size(%d) in nid(%llu)",
-			  next_nameoff, nid | 0ULL);
-		return -EFSCORRUPTED;
-	}
-
-	while (de < end) {
-		const char *de_name;
-		unsigned int de_namelen;
-		unsigned int nameoff;
-
-		nameoff = le16_to_cpu(de->nameoff);
-		de_name = (char *)dentry_blk + nameoff;
-
-		/* the last dirent check */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
-			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
-
-		if (prev_name)
-			free(prev_name);
-		prev_name = cur_name;
-		cur_name = strndup(de_name, de_namelen);
-		if (!cur_name) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
-		erofs_dbg("traversed filename(%s)", cur_name);
-
-		/* corrupted entry check */
-		if (nameoff != next_nameoff) {
-			erofs_err("bogus dirent with nameoff(%u): expected(%d) @ nid %llu, block %u, idx %u",
-				  nameoff, next_nameoff, nid | 0ULL,
-				  block, idx);
-			ret = -EFSCORRUPTED;
-			goto out;
-		}
-
-		if (nameoff + de_namelen > maxsize ||
-				de_namelen > EROFS_NAME_LEN) {
-			erofs_err("bogus dirent with namelen(%u) @ nid %llu, block %u, idx %u",
-				  de_namelen, nid | 0ULL, block, idx);
-			ret = -EFSCORRUPTED;
-			goto out;
-		}
-
-		if (prev_name && (strcmp(prev_name, cur_name) >= 0)) {
-			erofs_err("wrong dirent name order @ nid %llu block %u idx %u: prev(%s), cur(%s)",
-				  nid | 0ULL, block, idx,
-				  prev_name, cur_name);
-			ret = -EFSCORRUPTED;
-			goto out;
-		}
-
-		if (is_dot_dotdot(cur_name)) {
-			if (!check_special_dentry(de, de_namelen, nid, pnid)) {
-				ret = -EFSCORRUPTED;
-				goto out;
-			}
-		} else {
-			erofs_check_inode(nid, de->nid);
-		}
-
-		if (fsckcfg.corrupted) {
-			ret = -EFSCORRUPTED;
-			goto out;
-		}
-
-		next_nameoff += de_namelen;
-		++de;
-		++idx;
-	}
-
-out:
-	if (prev_name)
-		free(prev_name);
-	if (cur_name)
-		free(cur_name);
-
-	erofs_dbg("traversing ... done nid(%llu)", nid | 0ULL);
-	return ret;
-}
-
 static int verify_uncompressed_inode(struct erofs_inode *inode)
 {
 	struct erofs_map_blocks map = {
@@ -479,12 +365,18 @@ static int erofs_verify_inode_data(struct erofs_inode *inode)
 	return ret;
 }
 
-static void erofs_check_inode(erofs_nid_t pnid, erofs_nid_t nid)
+static int erofsfsck_chk_dirents(struct erofs_dir_context *ctx)
+{
+	if (ctx->dot_dotdot)
+		return 0;
+
+	return erofsfsck_check_inode(ctx->dir->nid, ctx->de_nid);
+}
+
+static int erofsfsck_check_inode(erofs_nid_t pnid, erofs_nid_t nid)
 {
 	int ret;
 	struct erofs_inode inode;
-	char buf[EROFS_BLKSIZ];
-	erofs_off_t offset;
 
 	erofs_dbg("check inode: nid(%llu)", nid | 0ULL);
 
@@ -507,44 +399,21 @@ static void erofs_check_inode(erofs_nid_t pnid, erofs_nid_t nid)
 	if (ret)
 		goto out;
 
-	if ((inode.i_mode & S_IFMT) != S_IFDIR)
-		goto out;
-
-	offset = 0;
-	while (offset < inode.i_size) {
-		erofs_blk_t block = erofs_blknr(offset);
-		erofs_off_t maxsize = min_t(erofs_off_t,
-					inode.i_size - offset, EROFS_BLKSIZ);
-		struct erofs_dirent *de = (void *)buf;
-
-		unsigned int nameoff;
-
-		ret = erofs_pread(&inode, buf, maxsize, offset);
-		if (ret) {
-			erofs_err("I/O error occurred when reading dirents @ nid %llu, block %u: %d",
-				  nid | 0ULL, block, ret);
-			goto out;
-		}
-
-		nameoff = le16_to_cpu(de->nameoff);
-		if (nameoff < sizeof(struct erofs_dirent) ||
-				nameoff >= PAGE_SIZE) {
-			erofs_err("invalid de[0].nameoff %u @ nid %llu block %u: %d",
-				  nameoff, nid | 0ULL, block, ret);
-			ret = -EFSCORRUPTED;
-			goto out;
-		}
-
-		ret = traverse_dirents(pnid, nid, buf, block,
-				       nameoff, maxsize);
-		if (ret)
-			goto out;
+	/* XXXX: the dir depth should be restricted in order to avoid loops */
+	if ((inode.i_mode & S_IFMT) == S_IFDIR) {
+		struct erofs_dir_context ctx = {
+			.flags = EROFS_READDIR_VALID_PNID,
+			.pnid = pnid,
+			.dir = &inode,
+			.cb = erofsfsck_chk_dirents,
+		};
 
-		offset += maxsize;
+		ret = erofs_iterate_dir(&ctx, true);
 	}
 out:
 	if (ret && ret != -EIO)
 		fsckcfg.corrupted = true;
+	return ret;
 }
 
 int main(int argc, char **argv)
@@ -583,12 +452,11 @@ int main(int argc, char **argv)
 		goto exit_dev_close;
 	}
 
-	erofs_check_inode(sbi.root_nid, sbi.root_nid);
-
+	err = erofsfsck_check_inode(sbi.root_nid, sbi.root_nid);
 	if (fsckcfg.corrupted) {
 		erofs_err("Found some filesystem corruption");
 		err = -EFSCORRUPTED;
-	} else {
+	} else if (!err) {
 		erofs_info("No error found");
 		if (fsckcfg.print_comp_ratio) {
 			double comp_ratio =
-- 
2.20.1