[PATCH 6.12.y] f2fs: fix false alarm of lockdep on cp_global_sem lock

[Sasha Levin <sashal@kernel.org>]

From: Chao Yu <chao@kernel.org>

[ Upstream commit 6a5e3de9c2bb0b691d16789a5d19e9276a09b308 ]

lockdep reported a potential deadlock:

a) TCMU device removal context:
 - call del_gendisk() to get q->q_usage_counter
 - call start_flush_work() to get work_completion of wb->dwork
b) f2fs writeback context:
 - in wb_workfn(), which holds work_completion of wb->dwork
 - call f2fs_balance_fs() to get sbi->gc_lock
c) f2fs vfs_write context:
 - call f2fs_gc() to get sbi->gc_lock
 - call f2fs_write_checkpoint() to get sbi->cp_global_sem
d) f2fs mount context:
 - call recover_fsync_data() to get sbi->cp_global_sem
 - call f2fs_check_and_fix_write_pointer() to call blkdev_report_zones()
   that goes down to blk_mq_alloc_request and get q->q_usage_counter

Original callstack is in Closes tag.

However, I think this is a false alarm due to before mount returns
successfully (context d), we can not access file therein via vfs_write
(context c).

Let's introduce per-sb cp_global_sem_key, and assign the key for
cp_global_sem, so that lockdep can recognize cp_global_sem from
different super block correctly.

A lot of work are done by Shin'ichiro Kawasaki, thanks a lot for
the work.

Fixes: c426d99127b1 ("f2fs: Check write pointer consistency of open zones")
Cc: stable@kernel.org
Reported-and-tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/linux-f2fs-devel/20260218125237.3340441-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[ adapted context to use `init_f2fs_rwsem()` instead of the not-yet-backported `init_f2fs_rwsem_trace()` macro ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/f2fs/f2fs.h  |  3 +++
 fs/f2fs/super.c | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ab0d9ed02092c..b094fdaf318dd 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1858,6 +1858,9 @@ struct f2fs_sb_info {
 	spinlock_t iostat_lat_lock;
 	struct iostat_lat_info *iostat_io_lat;
 #endif
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lock_class_key cp_global_sem_key;
+#endif
 };
 
 /* Definitions to access f2fs_sb_info */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index f25a259f37f12..1bce35d6f4e25 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4490,6 +4490,11 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	init_f2fs_rwsem(&sbi->gc_lock);
 	mutex_init(&sbi->writepages);
 	init_f2fs_rwsem(&sbi->cp_global_sem);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	lockdep_register_key(&sbi->cp_global_sem_key);
+	lockdep_set_class(&sbi->cp_global_sem.internal_rwsem,
+					&sbi->cp_global_sem_key);
+#endif
 	init_f2fs_rwsem(&sbi->node_write);
 	init_f2fs_rwsem(&sbi->node_change);
 	spin_lock_init(&sbi->stat_lock);
@@ -4963,6 +4968,9 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 free_sbi:
 	if (sbi->s_chksum_driver)
 		crypto_free_shash(sbi->s_chksum_driver);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	lockdep_unregister_key(&sbi->cp_global_sem_key);
+#endif
 	kfree(sbi);
 	sb->s_fs_info = NULL;
 
@@ -5015,6 +5023,9 @@ static void kill_f2fs_super(struct super_block *sb)
 	/* Release block devices last, after fscrypt_destroy_keyring(). */
 	if (sbi) {
 		destroy_device_list(sbi);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+		lockdep_unregister_key(&sbi->cp_global_sem_key);
+#endif
 		kfree(sbi);
 		sb->s_fs_info = NULL;
 	}
-- 
2.53.0