Date:   Sat,  9 Oct 2021 21:22:39 -0700
From:   Stefan Schaeckeler <schaecsn@....net>
To:     richard@....at, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Stefan Schaeckeler <schaecsn@....net>,
        Stefan Schaeckeler <sschaeck@...co.com>
Subject: [PATCH v2] ubifs: ubifs to export filesystem error counters

Not all ubifs filesystem errors are propagated to userspace.

Export bad magic, bad node and crc errors via sysfs. This allows userspace
to notice filesystem errors:

 /sys/fs/ubifs/ubiX_Y/errors_magic
 /sys/fs/ubifs/ubiX_Y/errors_node
 /sys/fs/ubifs/ubiX_Y/errors_crc

The counters are reset to 0 with a remount.

Signed-off-by: Stefan Schaeckeler <sschaeck@...co.com>
---
Changes in v2:
  - merged sysfs.h header into ubifs.h.
  - io.c: wrapped incrementing error counters into new functions
    record_*_error().
  - sysfs.c: removed sysfs write callback for clearing stats.
  - sysfs.c: ubifs_sysfs_register(): free c->stats on error.
  - sysfs.c: ubifs_attr_show(): use sysfs_emit().

 fs/ubifs/Makefile |   2 +-
 fs/ubifs/io.c     |  21 +++++++
 fs/ubifs/super.c  |  16 ++++-
 fs/ubifs/sysfs.c  | 153 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/ubifs/ubifs.h  |  35 +++++++++++
 5 files changed, 225 insertions(+), 2 deletions(-)
 create mode 100644 fs/ubifs/sysfs.c

diff --git a/fs/ubifs/Makefile b/fs/ubifs/Makefile
index 5c4b845754a7..314c80b24a76 100644
--- a/fs/ubifs/Makefile
+++ b/fs/ubifs/Makefile
@@ -5,7 +5,7 @@ ubifs-y += shrinker.o journal.o file.o dir.o super.o sb.o io.o
 ubifs-y += tnc.o master.o scan.o replay.o log.o commit.o gc.o orphan.o
 ubifs-y += budget.o find.o tnc_commit.o compress.o lpt.o lprops.o
 ubifs-y += recovery.o ioctl.o lpt_commit.o tnc_misc.o debug.o
-ubifs-y += misc.o
+ubifs-y += misc.o sysfs.o
 ubifs-$(CONFIG_FS_ENCRYPTION) += crypto.o
 ubifs-$(CONFIG_UBIFS_FS_XATTR) += xattr.o
 ubifs-$(CONFIG_UBIFS_FS_AUTHENTICATION) += auth.o
diff --git a/fs/ubifs/io.c b/fs/ubifs/io.c
index 00b61dba62b7..789a7813f3fa 100644
--- a/fs/ubifs/io.c
+++ b/fs/ubifs/io.c
@@ -194,6 +194,24 @@ int ubifs_is_mapped(const struct ubifs_info *c, int lnum)
 	return err;
 }

+static void record_magic_error(struct ubifs_stats_info *stats)
+{
+	if (stats)
+		stats->magic_errors++;
+}
+
+static void record_node_error(struct ubifs_stats_info *stats)
+{
+	if (stats)
+		stats->node_errors++;
+}
+
+static void record_crc_error(struct ubifs_stats_info *stats)
+{
+	if (stats)
+		stats->crc_errors++;
+}
+
 /**
  * ubifs_check_node - check node.
  * @c: UBIFS file-system description object
@@ -238,6 +256,7 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int len,
 		if (!quiet)
 			ubifs_err(c, "bad magic %#08x, expected %#08x",
 				  magic, UBIFS_NODE_MAGIC);
+		record_magic_error(c->stats);
 		err = -EUCLEAN;
 		goto out;
 	}
@@ -246,6 +265,7 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int len,
 	if (type < 0 || type >= UBIFS_NODE_TYPES_CNT) {
 		if (!quiet)
 			ubifs_err(c, "bad node type %d", type);
+		record_node_error(c->stats);
 		goto out;
 	}

@@ -270,6 +290,7 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int len,
 		if (!quiet)
 			ubifs_err(c, "bad CRC: calculated %#08x, read %#08x",
 				  crc, node_crc);
+		record_crc_error(c->stats);
 		err = -EUCLEAN;
 		goto out;
 	}
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index f0fb25727d96..a4e3a143fb1b 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1264,6 +1264,10 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		return err;

+	err = ubifs_sysfs_register(c);
+	if (err)
+		goto out_debugging;
+
 	err = check_volume_empty(c);
 	if (err)
 		goto out_free;
@@ -1641,6 +1645,8 @@ static int mount_ubifs(struct ubifs_info *c)
 	vfree(c->sbuf);
 	kfree(c->bottom_up_buf);
 	kfree(c->sup_node);
+	ubifs_sysfs_unregister(c);
+out_debugging:
 	ubifs_debugging_exit(c);
 	return err;
 }
@@ -1684,6 +1690,7 @@ static void ubifs_umount(struct ubifs_info *c)
 	kfree(c->bottom_up_buf);
 	kfree(c->sup_node);
 	ubifs_debugging_exit(c);
+	ubifs_sysfs_unregister(c);
 }

 /**
@@ -2436,14 +2443,20 @@ static int __init ubifs_init(void)

 	dbg_debugfs_init();

+	err = ubifs_sysfs_init();
+	if (err)
+		goto out_dbg;
+
 	err = register_filesystem(&ubifs_fs_type);
 	if (err) {
 		pr_err("UBIFS error (pid %d): cannot register file system, error %d",
 		       current->pid, err);
-		goto out_dbg;
+		goto out_sysfs;
 	}
 	return 0;

+out_sysfs:
+	ubifs_sysfs_exit();
 out_dbg:
 	dbg_debugfs_exit();
 	ubifs_compressors_exit();
@@ -2462,6 +2475,7 @@ static void __exit ubifs_exit(void)
 	WARN_ON(atomic_long_read(&ubifs_clean_zn_cnt) != 0);

 	dbg_debugfs_exit();
+	ubifs_sysfs_exit();
 	ubifs_compressors_exit();
 	unregister_shrinker(&ubifs_shrinker_info);

diff --git a/fs/ubifs/sysfs.c b/fs/ubifs/sysfs.c
new file mode 100644
index 000000000000..0b6f79b6e2e8
--- /dev/null
+++ b/fs/ubifs/sysfs.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This file is part of UBIFS.
+ *
+ * Copyright (C) 2021 Cisco Systems
+ *
+ * Author: Stefan Schaeckeler
+ */
+
+
+#include <linux/fs.h>
+#include "ubifs.h"
+
+enum attr_id_t {
+	attr_errors_magic,
+	attr_errors_node,
+	attr_errors_crc,
+};
+
+struct ubifs_attr {
+	struct attribute attr;
+	enum attr_id_t attr_id;
+};
+
+#define UBIFS_ATTR(_name, _mode, _id)					\
+static struct ubifs_attr ubifs_attr_##_name = {				\
+	.attr = {.name = __stringify(_name), .mode = _mode },		\
+	.attr_id = attr_##_id,						\
+}
+
+#define UBIFS_ATTR_FUNC(_name, _mode) UBIFS_ATTR(_name, _mode, _name)
+
+UBIFS_ATTR_FUNC(errors_magic, 0444);
+UBIFS_ATTR_FUNC(errors_crc, 0444);
+UBIFS_ATTR_FUNC(errors_node, 0444);
+
+#define ATTR_LIST(name) (&ubifs_attr_##name.attr)
+
+static struct attribute *ubifs_attrs[] = {
+	ATTR_LIST(errors_magic),
+	ATTR_LIST(errors_node),
+	ATTR_LIST(errors_crc),
+	NULL,
+};
+
+static ssize_t ubifs_attr_show(struct kobject *kobj,
+			       struct attribute *attr, char *buf)
+{
+	struct ubifs_info *sbi = container_of(kobj, struct ubifs_info,
+					      kobj);
+
+	struct ubifs_attr *a = container_of(attr, struct ubifs_attr, attr);
+
+	switch (a->attr_id) {
+	case attr_errors_magic:
+		return sysfs_emit(buf, "%u\n", sbi->stats->magic_errors);
+	case attr_errors_node:
+		return sysfs_emit(buf, "%u\n", sbi->stats->node_errors);
+	case attr_errors_crc:
+		return sysfs_emit(buf, "%u\n", sbi->stats->crc_errors);
+	}
+	return 0;
+};
+
+static void ubifs_sb_release(struct kobject *kobj)
+{
+	struct ubifs_info *c = container_of(kobj, struct ubifs_info, kobj);
+
+	complete(&c->kobj_unregister);
+}
+
+static const struct sysfs_ops ubifs_attr_ops = {
+	.show	= ubifs_attr_show,
+};
+
+static struct kobj_type ubifs_sb_ktype = {
+	.default_attrs	= ubifs_attrs,
+	.sysfs_ops	= &ubifs_attr_ops,
+	.release	= ubifs_sb_release,
+};
+
+static struct kobj_type ubifs_ktype = {
+	.sysfs_ops	= &ubifs_attr_ops,
+};
+
+static struct kset ubifs_kset = {
+	.kobj	= {.ktype = &ubifs_ktype},
+};
+
+int ubifs_sysfs_register(struct ubifs_info *c)
+{
+	int ret, n;
+	char dfs_dir_name[UBIFS_DFS_DIR_LEN+1];
+
+	c->stats = kzalloc(sizeof(struct ubifs_stats_info), GFP_KERNEL);
+	if (!c->stats) {
+		ret = -ENOMEM;
+		goto out_last;
+	}
+	n = snprintf(dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+		     c->vi.ubi_num, c->vi.vol_id);
+
+	if (n == UBIFS_DFS_DIR_LEN) {
+		/* The array size is too small */
+		ret = -EINVAL;
+		goto out_free;
+	}
+
+	c->kobj.kset = &ubifs_kset;
+	init_completion(&c->kobj_unregister);
+
+	ret = kobject_init_and_add(&c->kobj, &ubifs_sb_ktype, NULL,
+				   "%s", dfs_dir_name);
+	if (ret)
+		goto out_put;
+
+	return 0;
+
+out_put:
+	kobject_put(&c->kobj);
+	wait_for_completion(&c->kobj_unregister);
+out_free:
+	kfree(c->stats);
+out_last:
+	ubifs_err(c, "cannot create sysfs entry for ubifs%d_%d, error %d\n",
+		  c->vi.ubi_num, c->vi.vol_id, ret);
+	return ret;
+}
+
+void ubifs_sysfs_unregister(struct ubifs_info *c)
+{
+	kobject_del(&c->kobj);
+	kobject_put(&c->kobj);
+	wait_for_completion(&c->kobj_unregister);
+
+	kfree(c->stats);
+}
+
+int __init ubifs_sysfs_init(void)
+{
+	int ret;
+
+	kobject_set_name(&ubifs_kset.kobj, "ubifs");
+	ubifs_kset.kobj.parent = fs_kobj;
+	ret = kset_register(&ubifs_kset);
+
+	return ret;
+}
+
+void ubifs_sysfs_exit(void)
+{
+	kset_unregister(&ubifs_kset);
+}
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index c38066ce9ab0..f55828c0a300 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -27,6 +27,8 @@
 #include <linux/security.h>
 #include <linux/xattr.h>
 #include <linux/random.h>
+#include <linux/sysfs.h>
+#include <linux/completion.h>
 #include <crypto/hash_info.h>
 #include <crypto/hash.h>
 #include <crypto/algapi.h>
@@ -155,6 +157,13 @@
 #define UBIFS_HMAC_ARR_SZ 0
 #endif

+/*
+ * The UBIFS sysfs directory name pattern and maximum name length (3 for "ubi"
+ * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
+ */
+#define UBIFS_DFS_DIR_NAME "ubi%d_%d"
+#define UBIFS_DFS_DIR_LEN  (3 + 1 + 2*2 + 1)
+
 /*
  * Lockdep classes for UBIFS inode @ui_mutex.
  */
@@ -990,6 +999,18 @@ struct ubifs_budg_info {
 	int dent_budget;
 };

+/**
+ * ubifs_stats_info - per-FS statistics information.
+ * @magic_errors: number of bad magic numbers (will be reset with a new mount).
+ * @node_errors: number of bad nodes (will be reset with a new mount).
+ * @crc_errors: number of bad crcs (will be reset with a new mount).
+ */
+struct ubifs_stats_info {
+	unsigned int magic_errors;
+	unsigned int node_errors;
+	unsigned int crc_errors;
+};
+
 struct ubifs_debug_info;

 /**
@@ -1251,6 +1272,10 @@ struct ubifs_debug_info;
  * @mount_opts: UBIFS-specific mount options
  *
  * @dbg: debugging-related information
+ * @stats: statistics exported over sysfs
+ *
+ * @kobj: kobject for /sys/fs/ubifs/
+ * @kobj_unregister: completion to unregister sysfs kobject
  */
 struct ubifs_info {
 	struct super_block *vfs_sb;
@@ -1286,6 +1311,9 @@ struct ubifs_info {
 	spinlock_t cs_lock;
 	wait_queue_head_t cmt_wq;

+	struct kobject kobj;
+	struct completion kobj_unregister;
+
 	unsigned int big_lpt:1;
 	unsigned int space_fixup:1;
 	unsigned int double_hash:1;
@@ -1493,6 +1521,7 @@ struct ubifs_info {
 	struct ubifs_mount_opts mount_opts;

 	struct ubifs_debug_info *dbg;
+	struct ubifs_stats_info *stats;
 };

 extern struct list_head ubifs_infos;
@@ -2072,6 +2101,12 @@ void ubifs_compress(const struct ubifs_info *c, const void *in_buf, int in_len,
 int ubifs_decompress(const struct ubifs_info *c, const void *buf, int len,
 		     void *out, int *out_len, int compr_type);

+/* sysfs.c */
+int ubifs_sysfs_init(void);
+void ubifs_sysfs_exit(void);
+int ubifs_sysfs_register(struct ubifs_info *c);
+void ubifs_sysfs_unregister(struct ubifs_info *c);
+
 #include "debug.h"
 #include "misc.h"
 #include "key.h"
--
2.33.0

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