Commit 6a5e3de9 authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: fix false alarm of lockdep on cp_global_sem lock 



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: c426d991 ("f2fs: Check write pointer consistency of open zones")
Cc: stable@kernel.org
Reported-and-tested-by: default avatarShin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/linux-f2fs-devel/20260218125237.3340441-1-shinichiro.kawasaki@wdc.com


Signed-off-by: default avatarShin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent 238e14eb

fs/f2fs/f2fs.h

+3 −0
Original line number Diff line number Diff line
@@ -2042,6 +2042,9 @@ 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 */

fs/f2fs/super.c

+11 −0
Original line number Diff line number Diff line
@@ -4964,6 +4964,11 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc) 
	init_f2fs_rwsem_trace(&sbi->gc_lock, sbi, LOCK_NAME_GC_LOCK);

	mutex_init(&sbi->writepages);

	init_f2fs_rwsem_trace(&sbi->cp_global_sem, sbi, LOCK_NAME_CP_GLOBAL);

#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_trace(&sbi->node_write, sbi, LOCK_NAME_NODE_WRITE);

	init_f2fs_rwsem_trace(&sbi->node_change, sbi, LOCK_NAME_NODE_CHANGE);

	spin_lock_init(&sbi->stat_lock);
@@ -5435,6 +5440,9 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc) 
free_sb_buf:

	kfree(raw_super);

free_sbi:

#ifdef CONFIG_DEBUG_LOCK_ALLOC

	lockdep_unregister_key(&sbi->cp_global_sem_key);

#endif

	kfree(sbi);

	sb->s_fs_info = NULL;
@@ -5516,6 +5524,9 @@ 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;

	}