f2fs: introduce proc/fs/f2fs/<dev>/fsck_stack node

SBI_NEED_FSCK is an indicator that fsck.f2fs needs to be triggered,
this flag is set in too many places. For some scenes that are not very
reproducible, adding stack information will help locate the problem.

Let's expose all fsck stack history in procfs.

Signed-off-by: Yangtao Li <frank.li@vivo.com>

fs/f2fs/f2fs.h

@@ -24,6 +24,7 @@
 #include <linux/quotaops.h>
 #include <linux/part_stat.h>
 #include <crypto/hash.h>
+#include <linux/stackdepot.h>
 
 #include <linux/fscrypt.h>
 #include <linux/fsverity.h>
@@ -117,6 +118,8 @@ typedef u32 nid_t;
 
 #define COMPRESS_EXT_NUM		16
 
+#define FSCK_STACK_DEPTH 64
+
 struct f2fs_mount_info {
 	unsigned int opt;
 	int write_io_size_bits;		/* Write IO size bits */
@@ -1748,6 +1751,8 @@ struct f2fs_sb_info {
 	unsigned int compress_watermark;	/* cache page watermark */
 	atomic_t compress_page_hit;		/* cache hit count */
 #endif
+	depot_stack_handle_t *fsck_stack;
+	unsigned int fsck_count;
 };
 
 struct f2fs_private_dio {
@@ -1959,9 +1964,35 @@ static inline bool is_sbi_flag_set(struct f2fs_sb_info *sbi, unsigned int type)
 	return test_bit(type, &sbi->s_flag);
 }
 
-static inline void set_sbi_flag(struct f2fs_sb_info *sbi, unsigned int type)
+static void set_sbi_flag(struct f2fs_sb_info *sbi, unsigned int type)
 {
 	set_bit(type, &sbi->s_flag);
+
+	if (unlikely(type ==  SBI_NEED_FSCK)) {
+		unsigned long entries[FSCK_STACK_DEPTH];
+		depot_stack_handle_t stack, *new;
+		unsigned int nr_entries;
+		int i;
+
+		nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
+		nr_entries = filter_irq_stacks(entries, nr_entries);
+		stack = stack_depot_save(entries, nr_entries, GFP_KERNEL);
+		if (!stack)
+			return;
+
+		/* Try to find an existing entry for this backtrace */
+		for (i = 0; i < sbi->fsck_count; i++)
+			if (sbi->fsck_stack[i] == stack)
+				return;
+
+		new = krealloc(sbi->fsck_stack, (sbi->fsck_count + 1) *
+			       sizeof(*sbi->fsck_stack), GFP_KERNEL);
+		if (!new)
+			return;
+
+		sbi->fsck_stack = new;
+		sbi->fsck_stack[sbi->fsck_count++] = stack;
+	}
 }
 
 static inline void clear_sbi_flag(struct f2fs_sb_info *sbi, unsigned int type)

fs/f2fs/sysfs.c

@@ -1131,6 +1131,29 @@ static int __maybe_unused iostat_info_seq_show(struct seq_file *seq,
 	return 0;
 }
 
+static int __maybe_unused fsck_stack_seq_show(struct seq_file *seq,
+						void *offset)
+{
+	struct super_block *sb = seq->private;
+	struct f2fs_sb_info *sbi = F2FS_SB(sb);
+	unsigned long *entries;
+	unsigned int nr_entries;
+	unsigned int i, j;
+
+	for (i = 0; i < sbi->fsck_count; i++) {
+		nr_entries = stack_depot_fetch(sbi->fsck_stack[i], &entries);
+		if (!entries)
+			return 0;
+
+		for (j = 0; j < nr_entries; j++)
+			seq_printf(seq, "%pS\n", (void *)entries[j]);
+
+		seq_putc(seq, '\n');
+	}
+
+	return 0;
+}
+
 static int __maybe_unused victim_bits_seq_show(struct seq_file *seq,
 						void *offset)
 {
@@ -1221,6 +1244,8 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 				iostat_info_seq_show, sb);
 		proc_create_single_data("victim_bits", S_IRUGO, sbi->s_proc,
 				victim_bits_seq_show, sb);
+		proc_create_single_data("fsck_stack", S_IRUGO, sbi->s_proc,
+				fsck_stack_seq_show, sb);
 	}
 	return 0;
 put_feature_list_kobj:
@@ -1242,6 +1267,7 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
 		remove_proc_entry("segment_info", sbi->s_proc);
 		remove_proc_entry("segment_bits", sbi->s_proc);
 		remove_proc_entry("victim_bits", sbi->s_proc);
+		remove_proc_entry("fsck_stack", sbi->s_proc);
 		remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
 	}