f2fs: sysfs: introduce inject_lock_timeout

This patch adds a new sysfs node in /sys/fs/f2fs/<disk>/inject_lock_timeout,
it relies on CONFIG_F2FS_FAULT_INJECTION kernel config.

It can be used to simulate different type of timeout in lock duration.

==========     ===============================
Flag_Value     Flag_Description
==========     ===============================
0x00000000     No timeout (default)
0x00000001     Simulate running time
0x00000002     Simulate IO type sleep time
0x00000003     Simulate Non-IO type sleep time
0x00000004     Simulate runnable time
==========     ===============================

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -948,3 +948,17 @@ Description:	This is a threshold, once a thread enters critical region that lock
 		elapsed time exceeds this threshold, f2fs will print tracepoint to dump information
 		of related context. This sysfs entry can be used to control the value of threshold,
 		by default, the value is 500 ms.
+
+What:		/sys/fs/f2fs/<disk>/inject_timeout_type
+Date:		December 2025
+Contact:	"Chao Yu" <chao@kernel.org>
+Description:	This sysfs entry can be used to change type of injected timeout:
+		==========     ===============================
+		Flag_Value     Flag_Description
+		==========     ===============================
+		0x00000000     No timeout (default)
+		0x00000001     Simulate running time
+		0x00000002     Simulate IO type sleep time
+		0x00000003     Simulate Non-IO type sleep time
+		0x00000004     Simulate runnable time
+		==========     ===============================

fs/f2fs/checkpoint.c

@@ -64,7 +64,7 @@ static inline void trace_lock_elapsed_time_end(struct f2fs_rwsem *sem,
 		return;
 
 	if (time_to_inject(sem->sbi, FAULT_LOCK_TIMEOUT))
-		f2fs_io_schedule_timeout_killable(DEFAULT_FAULT_TIMEOUT);
+		f2fs_schedule_timeout_killable(DEFAULT_FAULT_TIMEOUT, true);
 
 	get_lock_elapsed_time(&tts);
 

fs/f2fs/f2fs.h

@@ -73,7 +73,8 @@ enum {
 enum fault_option {
 	FAULT_RATE	= 1,	/* only update fault rate */
 	FAULT_TYPE	= 2,	/* only update fault type */
-	FAULT_ALL	= 4,	/* reset all fault injection options/stats */
+	FAULT_TIMEOUT	= 4,	/* only update fault timeout type */
+	FAULT_ALL	= 8,	/* reset all fault injection options/stats */
 };
 
 #ifdef CONFIG_F2FS_FAULT_INJECTION
@@ -83,6 +84,7 @@ struct f2fs_fault_info {
 	unsigned int inject_type;
 	/* Used to account total count of injection for each type */
 	unsigned int inject_count[FAULT_MAX];
+	unsigned int inject_lock_timeout;	/* inject lock timeout */
 };
 
 extern const char *f2fs_fault_name[FAULT_MAX];
@@ -184,6 +186,15 @@ enum f2fs_lock_name {
 	LOCK_NAME_IO_RWSEM,
 };
 
+enum f2fs_timeout_type {
+	TIMEOUT_TYPE_NONE,
+	TIMEOUT_TYPE_RUNNING,
+	TIMEOUT_TYPE_IO_SLEEP,
+	TIMEOUT_TYPE_NONIO_SLEEP,
+	TIMEOUT_TYPE_RUNNABLE,
+	TIMEOUT_TYPE_MAX,
+};
+
 /*
  * An implementation of an rwsem that is explicitly unfair to readers. This
  * prevents priority inversion when a low-priority reader acquires the read lock
@@ -4927,6 +4938,7 @@ static inline bool f2fs_need_verity(const struct inode *inode, pgoff_t idx)
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 extern int f2fs_build_fault_attr(struct f2fs_sb_info *sbi, unsigned long rate,
 					unsigned long type, enum fault_option fo);
+extern void f2fs_simulate_lock_timeout(struct f2fs_sb_info *sbi);
 #else
 static inline int f2fs_build_fault_attr(struct f2fs_sb_info *sbi,
 					unsigned long rate, unsigned long type,
@@ -4934,6 +4946,10 @@ static inline int f2fs_build_fault_attr(struct f2fs_sb_info *sbi,
 {
 	return 0;
 }
+static inline void f2fs_simulate_lock_timeout(struct f2fs_sb_info *sbi)
+{
+	return;
+}
 #endif
 
 static inline bool is_journalled_quota(struct f2fs_sb_info *sbi)
@@ -4984,14 +5000,14 @@ static inline void __f2fs_schedule_timeout(long timeout, bool io)
 #define f2fs_schedule_timeout(timeout)			\
 			__f2fs_schedule_timeout(timeout, false)
 
-static inline void f2fs_io_schedule_timeout_killable(long timeout)
+static inline void f2fs_schedule_timeout_killable(long timeout, bool io)
 {
 	unsigned long last_time = jiffies + timeout;
 
 	while (jiffies < last_time) {
 		if (fatal_signal_pending(current))
 			return;
-		__f2fs_schedule_timeout(DEFAULT_SCHEDULE_TIMEOUT, true);
+		__f2fs_schedule_timeout(DEFAULT_SCHEDULE_TIMEOUT, io);
 	}
 }
 

fs/f2fs/segment.c

@@ -372,7 +372,7 @@ static int __f2fs_commit_atomic_write(struct inode *inode)
 
 out:
 	if (time_to_inject(sbi, FAULT_ATOMIC_TIMEOUT))
-		f2fs_io_schedule_timeout_killable(DEFAULT_FAULT_TIMEOUT);
+		f2fs_schedule_timeout_killable(DEFAULT_FAULT_TIMEOUT, true);
 
 	if (ret) {
 		sbi->revoked_atomic_block += fi->atomic_write_cnt;

fs/f2fs/super.c

@@ -97,8 +97,57 @@ int f2fs_build_fault_attr(struct f2fs_sb_info *sbi, unsigned long rate,
 		f2fs_info(sbi, "build fault injection type: 0x%lx", type);
 	}
 
+	if (fo & FAULT_TIMEOUT) {
+		if (type >= TIMEOUT_TYPE_MAX)
+			return -EINVAL;
+		ffi->inject_lock_timeout = (unsigned int)type;
+		f2fs_info(sbi, "build fault timeout injection type: 0x%lx", type);
+	}
+
 	return 0;
 }
+
+static void inject_timeout(struct f2fs_sb_info *sbi)
+{
+	struct f2fs_fault_info *ffi = &F2FS_OPTION(sbi).fault_info;
+	enum f2fs_timeout_type type = ffi->inject_lock_timeout;
+	unsigned long start_time = jiffies;
+	unsigned long timeout = HZ;
+
+	switch (type) {
+	case TIMEOUT_TYPE_RUNNING:
+		while (!time_after(jiffies, start_time + timeout)) {
+			if (fatal_signal_pending(current))
+				return;
+			;
+		}
+		break;
+	case TIMEOUT_TYPE_IO_SLEEP:
+		f2fs_schedule_timeout_killable(timeout, true);
+		break;
+	case TIMEOUT_TYPE_NONIO_SLEEP:
+		f2fs_schedule_timeout_killable(timeout, false);
+		break;
+	case TIMEOUT_TYPE_RUNNABLE:
+		while (!time_after(jiffies, start_time + timeout)) {
+			if (fatal_signal_pending(current))
+				return;
+			schedule();
+		}
+		break;
+	default:
+		return;
+	}
+}
+
+void f2fs_simulate_lock_timeout(struct f2fs_sb_info *sbi)
+{
+	struct f2fs_lock_context lc;
+
+	f2fs_lock_op(sbi, &lc);
+	inject_timeout(sbi);
+	f2fs_unlock_op(sbi, &lc);
+}
 #endif
 
 /* f2fs-wide shrinker description */

fs/f2fs/sysfs.c

@@ -35,6 +35,7 @@ enum {
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 	FAULT_INFO_RATE,	/* struct f2fs_fault_info */
 	FAULT_INFO_TYPE,	/* struct f2fs_fault_info */
+	FAULT_INFO_TIMEOUT,	/* struct f2fs_fault_info */
 #endif
 	RESERVED_BLOCKS,	/* struct f2fs_sb_info */
 	CPRC_INFO,	/* struct ckpt_req_control */
@@ -529,6 +530,12 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 			return -EINVAL;
 		return count;
 	}
+	if (a->struct_type == FAULT_INFO_TIMEOUT) {
+		if (f2fs_build_fault_attr(sbi, 0, t, FAULT_TIMEOUT))
+			return -EINVAL;
+		f2fs_simulate_lock_timeout(sbi);
+		return count;
+	}
 #endif
 	if (a->struct_type == RESERVED_BLOCKS) {
 		spin_lock(&sbi->stat_lock);
@@ -1233,6 +1240,7 @@ STAT_INFO_RO_ATTR(gc_background_calls, gc_call_count[BACKGROUND]);
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 FAULT_INFO_GENERAL_RW_ATTR(FAULT_INFO_RATE, inject_rate);
 FAULT_INFO_GENERAL_RW_ATTR(FAULT_INFO_TYPE, inject_type);
+FAULT_INFO_GENERAL_RW_ATTR(FAULT_INFO_TIMEOUT, inject_lock_timeout);
 #endif
 
 /* RESERVED_BLOCKS ATTR */
@@ -1362,6 +1370,7 @@ static struct attribute *f2fs_attrs[] = {
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 	ATTR_LIST(inject_rate),
 	ATTR_LIST(inject_type),
+	ATTR_LIST(inject_lock_timeout),
 #endif
 	ATTR_LIST(data_io_flag),
 	ATTR_LIST(node_io_flag),