[PATCH] f2fs: avoid false shutdown fserror reports

[Wenjie Qi <qwjhust@gmail.com>]

F2FS records image errors and checkpoint-stop reasons through the same
s_error_work worker.  The ordinary f2fs_handle_error() path only updates
s_errors, but the worker still calls fserror_report_shutdown()
unconditionally after committing the superblock.

As a result, a metadata corruption report can be followed by a synthetic
FAN_FS_ERROR event with ESHUTDOWN and an invalid superblock file handle,
even though no stop reason was recorded.

Track whether save_stop_reason() actually changed the stop_reason array
and only report the shutdown fserror for that case.  Pure s_errors updates
still commit the superblock, but no longer generate a false shutdown event.

Fixes: 50faed607d32 ("f2fs: support to report fserror")
Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>
---
 fs/f2fs/f2fs.h  | 1 +
 fs/f2fs/super.c | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index f0a54883b88..fffb516b78f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1990,6 +1990,7 @@ struct f2fs_sb_info {
 	unsigned char stop_reason[MAX_STOP_REASON];	/* stop reason */
 	spinlock_t error_lock;			/* protect errors/stop_reason array */
 	bool error_dirty;			/* errors of sb is dirty */
+	bool stop_reason_dirty;			/* stop reason of sb is dirty */
 
 	/* For reclaimed segs statistics per each GC mode */
 	unsigned int gc_segment_mode;		/* GC state for reclaimed segments */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index ada8098f8b3..718feb854b1 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4616,6 +4616,7 @@ static void save_stop_reason(struct f2fs_sb_info *sbi, unsigned char reason)
 	spin_lock_irqsave(&sbi->error_lock, flags);
 	if (sbi->stop_reason[reason] < GENMASK(BITS_PER_BYTE - 1, 0))
 		sbi->stop_reason[reason]++;
+	sbi->stop_reason_dirty = true;
 	spin_unlock_irqrestore(&sbi->error_lock, flags);
 }
 
@@ -4623,6 +4624,7 @@ static void f2fs_record_stop_reason(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
 	unsigned long flags;
+	bool report_shutdown = false;
 	int err;
 
 	f2fs_down_write(&sbi->sb_lock);
@@ -4634,6 +4636,10 @@ static void f2fs_record_stop_reason(struct f2fs_sb_info *sbi)
 		sbi->error_dirty = false;
 	}
 	memcpy(raw_super->s_stop_reason, sbi->stop_reason, MAX_STOP_REASON);
+	if (sbi->stop_reason_dirty) {
+		report_shutdown = true;
+		sbi->stop_reason_dirty = false;
+	}
 	spin_unlock_irqrestore(&sbi->error_lock, flags);
 
 	err = f2fs_commit_super(sbi, false);
@@ -4644,7 +4650,8 @@ static void f2fs_record_stop_reason(struct f2fs_sb_info *sbi)
 			"f2fs_commit_super fails to record stop_reason, err:%d",
 			err);
 
-	fserror_report_shutdown(sbi->sb, GFP_NOFS);
+	if (report_shutdown)
+		fserror_report_shutdown(sbi->sb, GFP_NOFS);
 }
 
 void f2fs_save_errors(struct f2fs_sb_info *sbi, unsigned char flag)
-- 
2.43.0