[RFC PATCH mtd-utils 058/110] fsck.ubifs: Add inconsistent problem handling asking function

[Zhihao Cheng]

There are four dimensions to define the type of inconsistent problems:
 1. fixable: Some inconsistent problems can't be fixed, for example
    corrupted superblock. Un-fixable problem will abort program.
 2. must fix: Some inconsistent problems can be ignored(eg. incorrect
    isize), but some are not(eg. corrupted TNC), which will affect the
    subsequent fsck steps.
 3. drop data: Some fixing methods will drop user data, which is
    unacceptable for safe mode. If it happens, fsck will be aborted.
 4. need rebuild: Some inconsistent problems depends on rebuilding
    filesystem to be fixed(eg. corrupted master node, corrupted TNC).
Define an asking function to handle above kinds of inconsistent problems.

Signed-off-by: Zhihao Cheng <chengzhihao1 at huawei.com>
---
 ubifs-utils/Makemodule.am           |   3 +-
 ubifs-utils/fsck.ubifs/fsck.ubifs.h |   3 +
 ubifs-utils/fsck.ubifs/problem.c    | 111 ++++++++++++++++++++++++++++++++++++
 3 files changed, 116 insertions(+), 1 deletion(-)
 create mode 100644 ubifs-utils/fsck.ubifs/problem.c

diff --git a/ubifs-utils/Makemodule.am b/ubifs-utils/Makemodule.am
index 0ed91dff..faff911f 100644
--- a/ubifs-utils/Makemodule.am
+++ b/ubifs-utils/Makemodule.am
@@ -79,7 +79,8 @@ fsck_ubifs_SOURCES = \
 	$(common_SOURCES) \
 	$(libubifs_SOURCES) \
 	ubifs-utils/fsck.ubifs/fsck.ubifs.h \
-	ubifs-utils/fsck.ubifs/fsck.ubifs.c
+	ubifs-utils/fsck.ubifs/fsck.ubifs.c \
+	ubifs-utils/fsck.ubifs/problem.c
 
 fsck_ubifs_LDADD = libmtd.a libubi.a $(ZLIB_LIBS) $(LZO_LIBS) $(ZSTD_LIBS) $(UUID_LIBS) $(LIBSELINUX_LIBS) $(OPENSSL_LIBS) -lm -lpthread
 fsck_ubifs_CPPFLAGS = $(AM_CPPFLAGS) $(ZLIB_CFLAGS) $(LZO_CFLAGS) $(ZSTD_CFLAGS) $(UUID_CFLAGS) $(LIBSELINUX_CFLAGS) \
diff --git a/ubifs-utils/fsck.ubifs/fsck.ubifs.h b/ubifs-utils/fsck.ubifs/fsck.ubifs.h
index d267dd24..b9783c15 100644
--- a/ubifs-utils/fsck.ubifs/fsck.ubifs.h
+++ b/ubifs-utils/fsck.ubifs/fsck.ubifs.h
@@ -88,4 +88,7 @@ static inline const char *mode_name(const struct ubifs_info *c)
 /* Exit code for fsck program. */
 extern int exit_code;
 
+/* problem.c */
+bool fix_problem(const struct ubifs_info *c, int problem_type);
+
 #endif
diff --git a/ubifs-utils/fsck.ubifs/problem.c b/ubifs-utils/fsck.ubifs/problem.c
new file mode 100644
index 00000000..9a8c2e06
--- /dev/null
+++ b/ubifs-utils/fsck.ubifs/problem.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024, Huawei Technologies Co, Ltd.
+ *
+ * Authors: Zhihao Cheng <chengzhihao1 at huawei.com>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+#include "ubifs.h"
+#include "defs.h"
+#include "debug.h"
+#include "fsck.ubifs.h"
+
+/*
+ * problem flags.
+ *
+ * PROBLEM_FIXABLE: problem is fixable, unsolvable problem such as corrupted
+ *		    super block will abort the fsck program
+ * PROBLEM_MUST_FIX: problem must be fixed because it will affect the subsequent
+ *		     fsck process, otherwise aborting the fsck program
+ * PROBLEM_DROP_DATA: user data could be dropped after fixing the problem
+ * PROBLEM_NEED_REBUILD: rebuilding filesystem is needed to fix the problem
+ */
+#define PROBLEM_FIXABLE		(1<<0)
+#define PROBLEM_MUST_FIX	(1<<1)
+#define PROBLEM_DROP_DATA	(1<<2)
+#define PROBLEM_NEED_REBUILD	(1<<3)
+
+struct fsck_problem {
+	unsigned int flags;
+	const char *desc;
+};
+
+static const struct fsck_problem problem_table[] = {};
+
+static void print_problem(const struct ubifs_info *c,
+			  const struct fsck_problem *problem)
+{
+	log_out(c, "problem: %s", problem->desc);
+}
+
+static void fatal_error(const struct ubifs_info *c,
+			const struct fsck_problem *problem)
+{
+	if (!(problem->flags & PROBLEM_FIXABLE))
+		log_out(c, "inconsistent problem cannot be fixed");
+	else
+		log_out(c, "inconsistent problem must be fixed");
+	exit(exit_code);
+}
+
+/**
+ * fix_problem - whether fixing the inconsistent problem
+ * @c: UBIFS file-system description object
+ * @problem_type: the type of inconsistent problem
+ *
+ * This function decides to fix/skip the inconsistent problem or abort the
+ * program according to @problem_type, returns %true if the problem should
+ * be fixed, returns %false if the problem will be skipped.
+ */
+bool fix_problem(const struct ubifs_info *c, int problem_type)
+{
+	bool ans, ask = true, def_y = true;
+	const struct fsck_problem *problem = &problem_table[problem_type];
+	const char *question = (problem->flags & PROBLEM_NEED_REBUILD) ?
+				"Rebuild filesystem?" : "Fix it?";
+
+	ubifs_assert(c, FSCK(c)->mode != REBUILD_MODE);
+
+	if (!(problem->flags & PROBLEM_FIXABLE)) {
+		exit_code |= FSCK_UNCORRECTED;
+		fatal_error(c, problem);
+	}
+
+	if (FSCK(c)->mode == CHECK_MODE ||
+	    ((problem->flags & PROBLEM_DROP_DATA) && FSCK(c)->mode == SAFE_MODE) ||
+	    ((problem->flags & PROBLEM_NEED_REBUILD) &&
+	     (FSCK(c)->mode == SAFE_MODE || FSCK(c)->mode == DANGER_MODE0)))
+		def_y = false;
+
+	if ((problem->flags & PROBLEM_NEED_REBUILD) &&
+	    (FSCK(c)->mode == DANGER_MODE0 || FSCK(c)->mode == DANGER_MODE1))
+		ask = false;
+
+	print_problem(c, problem);
+	ans = def_y;
+	if (FSCK(c)->mode == NORMAL_MODE) {
+		printf("%s[%d] (%s%s)", c->program_name, getpid(),
+		       c->dev_name ? : "-", mode_name(c));
+		if (prompt(question, def_y))
+			ans = true;
+		else
+			ans = false;
+	} else {
+		if (ask)
+			log_out(c, "%s %c\n", question, def_y ? 'y' : 'n');
+	}
+
+	if (!ans) {
+		exit_code |= FSCK_UNCORRECTED;
+		if (problem->flags & PROBLEM_MUST_FIX)
+			fatal_error(c, problem);
+	} else {
+		exit_code |= FSCK_NONDESTRUCT;
+	}
+
+	return ans;
+}
-- 
2.13.6