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FAILED: patch "[PATCH] f2fs: fix false alarm of lockdep on cp_global_sem lock" failed to apply to 5.15-stable tree

PATCH New [email protected] 2 participants 2 messages May 12 – May 20

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author maintainer
#0 lore raw

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 6a5e3de9c2bb0b691d16789a5d19e9276a09b308
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051240-overthrow-lumpiness-9c49@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6a5e3de9c2bb0b691d16789a5d19e9276a09b308 Mon Sep 17 00:00:00 2001
From: Chao Yu <[email protected]>
Date: Fri, 6 Mar 2026 12:24:20 +0000
Subject: [PATCH] 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 c426d99127b1 ("f2fs: Check write pointer consistency of open zones")
Cc [email protected]
Reported-and-tested-by Shin'ichiro Kawasaki <[email protected]>
Closes https://lore.kernel.org/linux-f2fs-devel/[email protected] open here
Signed-off-by Shin'ichiro Kawasaki <[email protected]>
Signed-off-by Chao Yu <[email protected]>
Signed-off-by Jaegeuk Kim <[email protected]>
fs/f2fs/f2fs.h +3 -0
index 39b97621456a..56c4af4b1737 100644
@@ -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
index f626e5ca089d..ae81af5a8d29 100644
@@ -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;
 	}
maintainer
#1 lore raw

PATCH 1/1 f2fs: fix false alarm of lockdep on cp_global_sem lock

From: Chao Yu <[email protected]>

[ 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 [email protected]
Reported-and-tested-by Shin'ichiro Kawasaki <[email protected]>
Closes https://lore.kernel.org/linux-f2fs-devel/[email protected] open here
Signed-off-by Shin'ichiro Kawasaki <[email protected]>
Signed-off-by Chao Yu <[email protected]>
Signed-off-by Jaegeuk Kim <[email protected]>
[ adapted to plain `struct rw_semaphore` (no `f2fs_rwsem` wrapper) and moved success-path `lockdep_unregister_key` from `kill_f2fs_super` to `f2fs_put_super` where sbi is actually freed ]
Signed-off-by Sasha Levin <[email protected]>
---
 fs/f2fs/f2fs.h  |  3 +++
 fs/f2fs/super.c | 11 +++++++++++
 2 files changed, 14 insertions(+)
fs/f2fs/f2fs.h +3 -0
index 31968257ad8e2..121d7c361b617 100644
@@ -1798,6 +1798,9 @@ 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
 };
 
 struct f2fs_private_dio {
fs/f2fs/super.c +11 -0
index 6f6368400ee46..595e6a6fcdad1 100644
@@ -1667,6 +1667,9 @@ static void f2fs_put_super(struct super_block *sb)
 		kvfree(sbi->write_io[i]);
 #ifdef CONFIG_UNICODE
 	utf8_unload(sb->s_encoding);
+#endif
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	lockdep_unregister_key(&sbi->cp_global_sem_key);
 #endif
 	kfree(sbi);
 }

@@ -4118,6 +4121,11 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	init_rwsem(&sbi->gc_lock);
 	mutex_init(&sbi->writepages);
 	init_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,
+					&sbi->cp_global_sem_key);
+#endif
 	init_rwsem(&sbi->node_write);
 	init_rwsem(&sbi->node_change);
 

@@ -4519,6 +4527,9 @@ 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);
 
 	/* give only one another chance */
Signature · 1 line
2.53.0