Date:   Sat, 18 Mar 2023 09:56:17 +0800
From:   ZhaoLong Wang <wangzhaolong1@...wei.com>
To:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <chengzhihao1@...wei.com>, <wangzhaolong1@...wei.com>,
        <yi.zhang@...wei.com>
Subject: [PATCH -next 1/5] ubi: Using the Fault Injection Framework to refactor the debugfs interface

To make debug parameters configurable at run time, use the
fault injection framework to reconstruct the debugfs interface.

Now, the file emulate_failures and fault_attr files control whether
to enable fault emmulation.

The file emulate_failures receives a mask that controls type and
process of fault injection. Generally, for ease of use, you can
directly enter a mask with all 1s.

echo 0xffff > /sys/kernel/debug/ubi/ubi0/emulate_failures

And you need to configure other fault-injection capabilities for
testing purpose:

echo 100 > /sys/kernel/debug/ubi/fault_inject/emulate_power_cut/probability
echo 15 > /sys/kernel/debug/ubi/fault_inject/emulate_power_cut/space
echo 2 > /sys/kernel/debug/ubi/fault_inject/emulate_power_cut/verbose
echo -1 > /sys/kernel/debug/ubi/fault_inject/emulate_power_cut/times

The CONFIG_MTD_UBI_FAULT_INJECTION to enable the Fault Injection is
added to kconfig.

Signed-off-by: ZhaoLong Wang <wangzhaolong1@...wei.com>
---
 drivers/mtd/ubi/Kconfig |   8 +++
 drivers/mtd/ubi/debug.c | 147 ++++++++++++++++------------------------
 drivers/mtd/ubi/debug.h |  91 ++++++++++++++++++++-----
 drivers/mtd/ubi/io.c    |  10 ++-
 drivers/mtd/ubi/ubi.h   |  37 ++--------
 5 files changed, 150 insertions(+), 143 deletions(-)

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 2ed77b7b3fcb..0a0180a3a54b 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -103,5 +103,13 @@ config MTD_UBI_BLOCK
 	   When selected, this feature will be built in the UBI driver.
 
 	   If in doubt, say "N".
+config MTD_UBI_FAULT_INJECTION
+	bool "Fault injection capability of UBI device"
+	default n
+	depends on FAULT_INJECTION_DEBUG_FS
+	help
+	   this option enable fault-injection support for UBI devices for
+	   testing purposes and is only interesting to developers.
 
+	   If unsure, say N.
 endif # MTD_UBI
diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index 27168f511d6d..2550522e2cd5 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -10,6 +10,23 @@
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/seq_file.h>
+#include <linux/fault-inject.h>
+
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+static DECLARE_FAULT_ATTR(fault_bitflips_attr);
+static DECLARE_FAULT_ATTR(fault_io_failures_attr);
+static DECLARE_FAULT_ATTR(fault_power_cut_attr);
+
+#define FAIL_ACTION(name, fault_attr)			\
+bool should_fail_##name(void)				\
+{							\
+	return should_fail(&fault_attr, 1);		\
+}
+
+FAIL_ACTION(bitflips,		fault_bitflips_attr)
+FAIL_ACTION(io_failures,	fault_io_failures_attr)
+FAIL_ACTION(power_cut,		fault_power_cut_attr)
+#endif
 
 
 /**
@@ -212,6 +229,31 @@ void ubi_dump_mkvol_req(const struct ubi_mkvol_req *req)
  */
 static struct dentry *dfs_rootdir;
 
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+static void dfs_create_fault_entry(struct dentry *parent)
+{
+	struct dentry *dir;
+
+	dir = debugfs_create_dir("fault_inject", parent);
+	if (IS_ERR_OR_NULL(dir)) {
+		int err = dir ? PTR_ERR(dir) : -ENODEV;
+
+		pr_warn("UBI error: cannot create \"fault_inject\" debugfs directory, error %d\n",
+			err);
+		return;
+	}
+
+	fault_create_debugfs_attr("emulate_bitflips", dir,
+				  &fault_bitflips_attr);
+
+	fault_create_debugfs_attr("emulate_io_failures", dir,
+				  &fault_io_failures_attr);
+
+	fault_create_debugfs_attr("emulate_power_cut", dir,
+				  &fault_power_cut_attr);
+}
+#endif
+
 /**
  * ubi_debugfs_init - create UBI debugfs directory.
  *
@@ -232,6 +274,10 @@ int ubi_debugfs_init(void)
 		return err;
 	}
 
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+	dfs_create_fault_entry(dfs_rootdir);
+#endif
+
 	return 0;
 }
 
@@ -268,27 +314,12 @@ static ssize_t dfs_file_read(struct file *file, char __user *user_buf,
 		val = d->chk_fastmap;
 	else if (dent == d->dfs_disable_bgt)
 		val = d->disable_bgt;
-	else if (dent == d->dfs_emulate_bitflips)
-		val = d->emulate_bitflips;
-	else if (dent == d->dfs_emulate_io_failures)
-		val = d->emulate_io_failures;
-	else if (dent == d->dfs_emulate_power_cut) {
-		snprintf(buf, sizeof(buf), "%u\n", d->emulate_power_cut);
+	else if (dent == d->dfs_emulate_failures) {
+		snprintf(buf, sizeof(buf), "%u\n", d->emulate_failures);
 		count = simple_read_from_buffer(user_buf, count, ppos,
 						buf, strlen(buf));
 		goto out;
-	} else if (dent == d->dfs_power_cut_min) {
-		snprintf(buf, sizeof(buf), "%u\n", d->power_cut_min);
-		count = simple_read_from_buffer(user_buf, count, ppos,
-						buf, strlen(buf));
-		goto out;
-	} else if (dent == d->dfs_power_cut_max) {
-		snprintf(buf, sizeof(buf), "%u\n", d->power_cut_max);
-		count = simple_read_from_buffer(user_buf, count, ppos,
-						buf, strlen(buf));
-		goto out;
-	}
-	else {
+	} else {
 		count = -EINVAL;
 		goto out;
 	}
@@ -330,20 +361,10 @@ static ssize_t dfs_file_write(struct file *file, const char __user *user_buf,
 		goto out;
 	}
 
-	if (dent == d->dfs_power_cut_min) {
-		if (kstrtouint(buf, 0, &d->power_cut_min) != 0)
-			count = -EINVAL;
-		goto out;
-	} else if (dent == d->dfs_power_cut_max) {
-		if (kstrtouint(buf, 0, &d->power_cut_max) != 0)
+	if (dent == d->dfs_emulate_failures) {
+		if (kstrtouint(buf, 0, &d->emulate_failures) != 0)
 			count = -EINVAL;
 		goto out;
-	} else if (dent == d->dfs_emulate_power_cut) {
-		if (kstrtoint(buf, 0, &val) != 0)
-			count = -EINVAL;
-		else
-			d->emulate_power_cut = val;
-		goto out;
 	}
 
 	if (buf[0] == '1')
@@ -363,10 +384,6 @@ static ssize_t dfs_file_write(struct file *file, const char __user *user_buf,
 		d->chk_fastmap = val;
 	else if (dent == d->dfs_disable_bgt)
 		d->disable_bgt = val;
-	else if (dent == d->dfs_emulate_bitflips)
-		d->emulate_bitflips = val;
-	else if (dent == d->dfs_emulate_io_failures)
-		d->emulate_io_failures = val;
 	else
 		count = -EINVAL;
 
@@ -386,6 +403,7 @@ static const struct file_operations dfs_fops = {
 	.owner  = THIS_MODULE,
 };
 
+
 /* As long as the position is less then that total number of erase blocks,
  * we still have more to print.
  */
@@ -533,32 +551,14 @@ int ubi_debugfs_init_dev(struct ubi_device *ubi)
 						 d->dfs_dir, (void *)ubi_num,
 						 &dfs_fops);
 
-	d->dfs_emulate_bitflips = debugfs_create_file("tst_emulate_bitflips",
-						      mode, d->dfs_dir,
-						      (void *)ubi_num,
-						      &dfs_fops);
-
-	d->dfs_emulate_io_failures = debugfs_create_file("tst_emulate_io_failures",
-							 mode, d->dfs_dir,
-							 (void *)ubi_num,
-							 &dfs_fops);
-
-	d->dfs_emulate_power_cut = debugfs_create_file("tst_emulate_power_cut",
-						       mode, d->dfs_dir,
-						       (void *)ubi_num,
-						       &dfs_fops);
-
-	d->dfs_power_cut_min = debugfs_create_file("tst_emulate_power_cut_min",
-						   mode, d->dfs_dir,
-						   (void *)ubi_num, &dfs_fops);
-
-	d->dfs_power_cut_max = debugfs_create_file("tst_emulate_power_cut_max",
-						   mode, d->dfs_dir,
-						   (void *)ubi_num, &dfs_fops);
-
 	debugfs_create_file("detailed_erase_block_info", S_IRUSR, d->dfs_dir,
 			    (void *)ubi_num, &eraseblk_count_fops);
 
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+	d->dfs_emulate_failures = debugfs_create_file("emulate_failures", mode,
+						      d->dfs_dir, (void *)ubi_num,
+						      &dfs_fops);
+#endif
 	return 0;
 }
 
@@ -571,36 +571,3 @@ void ubi_debugfs_exit_dev(struct ubi_device *ubi)
 	if (IS_ENABLED(CONFIG_DEBUG_FS))
 		debugfs_remove_recursive(ubi->dbg.dfs_dir);
 }
-
-/**
- * ubi_dbg_power_cut - emulate a power cut if it is time to do so
- * @ubi: UBI device description object
- * @caller: Flags set to indicate from where the function is being called
- *
- * Returns non-zero if a power cut was emulated, zero if not.
- */
-int ubi_dbg_power_cut(struct ubi_device *ubi, int caller)
-{
-	unsigned int range;
-
-	if ((ubi->dbg.emulate_power_cut & caller) == 0)
-		return 0;
-
-	if (ubi->dbg.power_cut_counter == 0) {
-		ubi->dbg.power_cut_counter = ubi->dbg.power_cut_min;
-
-		if (ubi->dbg.power_cut_max > ubi->dbg.power_cut_min) {
-			range = ubi->dbg.power_cut_max - ubi->dbg.power_cut_min;
-			ubi->dbg.power_cut_counter += get_random_u32_below(range);
-		}
-		return 0;
-	}
-
-	ubi->dbg.power_cut_counter--;
-	if (ubi->dbg.power_cut_counter)
-		return 0;
-
-	ubi_msg(ubi, "XXXXXXXXXXXXXXX emulating a power cut XXXXXXXXXXXXXXXX");
-	ubi_ro_mode(ubi);
-	return 1;
-}
diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
index 23676f32b681..bf843433a901 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -8,6 +8,18 @@
 #ifndef __UBI_DEBUG_H__
 #define __UBI_DEBUG_H__
 
+/**
+ * MASK_XXX: Mask for emulate_failures in ubi_debug_info.The mask is used to
+ * precisely control the type and process of fault injection.
+ */
+/* Emulate bit-flips */
+#define MASK_BITFLIPS		(1 << 0)
+/* Emulates -EIO during write/erase */
+#define MASK_IO_FAILURE		(1 << 1)
+/* Emulate a power cut when writing EC/VID header */
+#define MASK_POWER_CUT_EC	(1 << 2)
+#define MASK_POWER_CUT_VID	(1 << 3)
+
 void ubi_dump_flash(struct ubi_device *ubi, int pnum, int offset, int len);
 void ubi_dump_ec_hdr(const struct ubi_ec_hdr *ec_hdr);
 void ubi_dump_vid_hdr(const struct ubi_vid_hdr *vid_hdr);
@@ -64,46 +76,90 @@ static inline int ubi_dbg_is_bgt_disabled(const struct ubi_device *ubi)
 	return ubi->dbg.disable_bgt;
 }
 
+#ifdef CONFIG_MTD_UBI_FAULT_INJECTION
+
+extern bool should_fail_bitflips(void);
+extern bool should_fail_io_failures(void);
+extern bool should_fail_power_cut(void);
+
 /**
  * ubi_dbg_is_bitflip - if it is time to emulate a bit-flip.
  * @ubi: UBI device description object
  *
- * Returns non-zero if a bit-flip should be emulated, otherwise returns zero.
+ * Returns true if a bit-flip should be emulated, otherwise returns false.
  */
-static inline int ubi_dbg_is_bitflip(const struct ubi_device *ubi)
+static inline bool ubi_dbg_is_bitflip(const struct ubi_device *ubi)
 {
-	if (ubi->dbg.emulate_bitflips)
-		return !get_random_u32_below(200);
-	return 0;
+	if (ubi->dbg.emulate_failures & MASK_BITFLIPS)
+		return should_fail_bitflips();
+	return false;
 }
 
 /**
  * ubi_dbg_is_write_failure - if it is time to emulate a write failure.
  * @ubi: UBI device description object
  *
- * Returns non-zero if a write failure should be emulated, otherwise returns
- * zero.
+ * Returns true if a write failure should be emulated, otherwise returns
+ * false.
  */
-static inline int ubi_dbg_is_write_failure(const struct ubi_device *ubi)
+static inline bool ubi_dbg_is_write_failure(const struct ubi_device *ubi)
 {
-	if (ubi->dbg.emulate_io_failures)
-		return !get_random_u32_below(500);
-	return 0;
+	if (ubi->dbg.emulate_failures & MASK_IO_FAILURE)
+		return should_fail_io_failures();
+	return false;
 }
 
 /**
  * ubi_dbg_is_erase_failure - if its time to emulate an erase failure.
  * @ubi: UBI device description object
  *
- * Returns non-zero if an erase failure should be emulated, otherwise returns
- * zero.
+ * Returns true if an erase failure should be emulated, otherwise returns
+ * false.
  */
-static inline int ubi_dbg_is_erase_failure(const struct ubi_device *ubi)
+static inline bool ubi_dbg_is_erase_failure(const struct ubi_device *ubi)
+{
+	if (ubi->dbg.emulate_failures & MASK_IO_FAILURE)
+		return should_fail_io_failures();
+	return false;
+}
+
+/**
+ * ubi_dbg_power_cut - if it is time to emulate power cut.
+ * @ubi: UBI device description object
+ *
+ * Returns true if power cut should be emulated, otherwise returns false.
+ */
+static inline bool ubi_dbg_power_cut(const struct ubi_device *ubi,
+				     unsigned int caller)
+{
+	if (ubi->dbg.emulate_failures & caller)
+		return should_fail_power_cut();
+	return false;
+}
+
+#else /* CONFIG_MTD_UBI_FAULT_INJECTION */
+
+static inline bool ubi_dbg_is_bitflip(const struct ubi_device *ubi)
+{
+	return false;
+}
+
+static inline bool ubi_dbg_is_write_failure(const struct ubi_device *ubi)
+{
+	return false;
+}
+
+static inline bool ubi_dbg_is_erase_failure(const struct ubi_device *ubi)
+{
+	return false;
+}
+
+static inline bool ubi_dbg_power_cut(const struct ubi_device *ubi,
+				     unsigned int caller)
 {
-	if (ubi->dbg.emulate_io_failures)
-		return !get_random_u32_below(400);
-	return 0;
+	return false;
 }
+#endif
 
 static inline int ubi_dbg_chk_io(const struct ubi_device *ubi)
 {
@@ -125,5 +181,4 @@ static inline void ubi_enable_dbg_chk_fastmap(struct ubi_device *ubi)
 	ubi->dbg.chk_fastmap = 1;
 }
 
-int ubi_dbg_power_cut(struct ubi_device *ubi, int caller);
 #endif /* !__UBI_DEBUG_H__ */
diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index 01b644861253..906ad0811d52 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -821,8 +821,11 @@ int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
 	if (err)
 		return err;
 
-	if (ubi_dbg_power_cut(ubi, POWER_CUT_EC_WRITE))
+	if (ubi_dbg_power_cut(ubi, MASK_POWER_CUT_EC)) {
+		ubi_warn(ubi, "XXXXX emulating a power cut when writing EC header XXXXX");
+		ubi_ro_mode(ubi);
 		return -EROFS;
+	}
 
 	err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
 	return err;
@@ -1071,8 +1074,11 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 	if (err)
 		return err;
 
-	if (ubi_dbg_power_cut(ubi, POWER_CUT_VID_WRITE))
+	if (ubi_dbg_power_cut(ubi, MASK_POWER_CUT_VID)) {
+		ubi_warn(ubi, "XXXXX emulating a power cut when writing VID header XXXXX");
+		ubi_ro_mode(ubi);
 		return -EROFS;
+	}
 
 	err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			   ubi->vid_hdr_alsize);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index c8f1bd4fa100..e20e9a6f9c05 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -142,17 +142,6 @@ enum {
 	UBI_BAD_FASTMAP,
 };
 
-/*
- * Flags for emulate_power_cut in ubi_debug_info
- *
- * POWER_CUT_EC_WRITE: Emulate a power cut when writing an EC header
- * POWER_CUT_VID_WRITE: Emulate a power cut when writing a VID header
- */
-enum {
-	POWER_CUT_EC_WRITE = 0x01,
-	POWER_CUT_VID_WRITE = 0x02,
-};
-
 /**
  * struct ubi_vid_io_buf - VID buffer used to read/write VID info to/from the
  *			   flash.
@@ -395,46 +384,28 @@ struct ubi_volume_desc {
  * @chk_io: if UBI I/O extra checks are enabled
  * @chk_fastmap: if UBI fastmap extra checks are enabled
  * @disable_bgt: disable the background task for testing purposes
- * @emulate_bitflips: emulate bit-flips for testing purposes
- * @emulate_io_failures: emulate write/erase failures for testing purposes
- * @emulate_power_cut: emulate power cut for testing purposes
- * @power_cut_counter: count down for writes left until emulated power cut
- * @power_cut_min: minimum number of writes before emulating a power cut
- * @power_cut_max: maximum number of writes until emulating a power cut
+ * @emulate_failures: emulate failures for testing purposes
  * @dfs_dir_name: name of debugfs directory containing files of this UBI device
  * @dfs_dir: direntry object of the UBI device debugfs directory
  * @dfs_chk_gen: debugfs knob to enable UBI general extra checks
  * @dfs_chk_io: debugfs knob to enable UBI I/O extra checks
  * @dfs_chk_fastmap: debugfs knob to enable UBI fastmap extra checks
  * @dfs_disable_bgt: debugfs knob to disable the background task
- * @dfs_emulate_bitflips: debugfs knob to emulate bit-flips
- * @dfs_emulate_io_failures: debugfs knob to emulate write/erase failures
- * @dfs_emulate_power_cut: debugfs knob to emulate power cuts
- * @dfs_power_cut_min: debugfs knob for minimum writes before power cut
- * @dfs_power_cut_max: debugfs knob for maximum writes until power cut
+ * @dfs_emulate_failures: debugfs entry to control the fault injection type
  */
 struct ubi_debug_info {
 	unsigned int chk_gen:1;
 	unsigned int chk_io:1;
 	unsigned int chk_fastmap:1;
 	unsigned int disable_bgt:1;
-	unsigned int emulate_bitflips:1;
-	unsigned int emulate_io_failures:1;
-	unsigned int emulate_power_cut:2;
-	unsigned int power_cut_counter;
-	unsigned int power_cut_min;
-	unsigned int power_cut_max;
+	unsigned int emulate_failures;
 	char dfs_dir_name[UBI_DFS_DIR_LEN + 1];
 	struct dentry *dfs_dir;
 	struct dentry *dfs_chk_gen;
 	struct dentry *dfs_chk_io;
 	struct dentry *dfs_chk_fastmap;
 	struct dentry *dfs_disable_bgt;
-	struct dentry *dfs_emulate_bitflips;
-	struct dentry *dfs_emulate_io_failures;
-	struct dentry *dfs_emulate_power_cut;
-	struct dentry *dfs_power_cut_min;
-	struct dentry *dfs_power_cut_max;
+	struct dentry *dfs_emulate_failures;
 };
 
 /**
-- 
2.31.1

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