f2fs: fix false alarm of lockdep on cp_global_sem lock

[ 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>
[ re-anchored lockdep_register_key after init_f2fs_rwsem and placed lockdep_unregister_key before kfree(sbi) in f2fs_put_super instead of kill_f2fs_super ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index fb35f78e60bb33c3f90fa1912516e8422be8f17d..50847fd7e5504567f86aed8f89c000fe8291cfdd 100644 (file)
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1824,6 +1824,9 @@ 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 7614d93bd67fbd4ecc4a3babb5d387a045857b6d..c018d548e163481c4769a030f79fc82972daed96 100644 (file)
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1694,6 +1694,9 @@ static void f2fs_put_super(struct super_block *sb)
                kvfree(sbi->write_io[i]);
 #if IS_ENABLED(CONFIG_UNICODE)
        utf8_unload(sb->s_encoding);
+#endif
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+       lockdep_unregister_key(&sbi->cp_global_sem_key);
 #endif
        kfree(sbi);
 }
@@ -4380,6 +4383,11 @@ try_onemore:
        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);
@@ -4838,6 +4846,9 @@ free_sb_buf:
 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);
 
        /* give only one another chance */