Re: [PATCH] jbd2: assign different lock_class_key for different filesystem

Tetsuo Handa
2025-10-20T11:29:23Z

On 2025/10/20 18:31, Jan Kara wrote:
> On Sun 19-10-25 19:52:43, Tetsuo Handa wrote:
>> syzbot is reporting possibility of deadlock due to sharing lock_class_key
>> for jbd2_handle across ext4 and ocfs2. But one disk partition can't have
>> two filesystems at the same time, and how locks in journal_t interacts
>> with other filesystem specific locks can vary depending on filesystems.
>> Therefore, lockdep should treat locks in journal_t different locks if
>> the filesystem which allocated the journal_t differs.
>
> Thanks for debugging this. I agree with the idea of your solution but the
> implementation is just ugly. Just let the filesystem pass the lockdep key
> into jbd2_journal_init_dev() / jbd2_journal_init_inode() and make ext4 and
> ocfs2 functions initializing the journal each have its own lock_class_key
> declared and pass it to jbd2 functions. That way changes are much simpler
> and also jbd2 doesn't have to be aware about which filesystems are using
> it.

Well, do you mean something like below diff? If we can assume that only ext4
and ocfs2 are using jbd2, the diff becomes smaller...

fs/ext4/super.c | 6 +++-
fs/jbd2/journal.c | 68 ++++++++++++++++++++++++++++++++++++---------------
fs/ocfs2/journal.c | 6 +++-
include/linux/jbd2.h | 15 ++++++++---
4 files changed, 67 insertions(+), 28 deletions(-)

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 43b9297fe8a7..184d025341da 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1287,6 +1287,13 @@ struct journal_s
int (*j_bmap)(struct journal_s *journal, sector_t *block);
};

+struct jbd2_lock_class_keys {
+ const char *name;
+ struct lock_class_key jbd2_trans_commit_key, j_abort_mutex, j_barrier,
+ j_checkpoint_mutex, j_revoke_lock, j_list_lock, j_history_lock,
+ j_state_lock;
+};
+
#define jbd2_might_wait_for_commit(j) \
do { \
rwsem_acquire(&j->j_trans_commit_map, 0, 0, _THIS_IP_); \
@@ -1523,10 +1530,10 @@ extern void jbd2_journal_unlock_updates (journal_t *);

void jbd2_journal_wait_updates(journal_t *);

-extern journal_t * jbd2_journal_init_dev(struct block_device *bdev,
- struct block_device *fs_dev,
- unsigned long long start, int len, int bsize);
-extern journal_t * jbd2_journal_init_inode (struct inode *);
+extern journal_t *jbd2_journal_init_dev(struct block_device *bdev, struct block_device *fs_dev,
+ unsigned long long start, int len, int bsize,
+ struct jbd2_lock_class_keys *keys);
+extern journal_t *jbd2_journal_init_inode(struct inode *inode, struct jbd2_lock_class_keys *keys);
extern int jbd2_journal_update_format (journal_t *);
extern int jbd2_journal_check_used_features
(journal_t *, unsigned long, unsigned long, unsigned long);
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index d480b94117cd..775c1cfa452a 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1506,6 +1506,34 @@ static int journal_load_superblock(journal_t *journal)
return 0;
}

+#ifndef CONFIG_RT
+/* This change goes to include/linux/spinlock.h */
+#ifdef CONFIG_DEBUG_SPINLOCK
+#define spin_lock_init_with_key(lock, key) \
+ __raw_spin_lock_init(spinlock_check(lock), #lock, key, LD_WAIT_CONFIG)
+#else
+#define spin_lock_init_with_key(lock, key) do { spin_lock_init(lock); (void)(key); } while (0)
+#endif
+#else
+/* This change goes to include/linux/spinlock_rt.h */
+#define spin_lock_init_with_key(slock, key) __spin_lock_init(slock, #slock, key, false)
+#endif
+
+#ifndef CONFIG_RT
+/* This change goes to include/linux/rwlock.h */
+#ifdef CONFIG_DEBUG_SPINLOCK
+#define rwlock_init_with_key(lock, key) __rwlock_init((lock), #lock, key)
+#else
+#define rwlock_init_with_key(lock, key) do { rwlock_init(lock); (void)(key); } while (0)
+#endif
+#else
+/* This change goes to include/linux/rwlock_rt.h */
+#define rwlock_init_with_key(rwl, key) \
+ do { \
+ init_rwbase_rt(&(rwl)->rwbase); \
+ __rt_rwlock_init(rwl, #rwl, key); \
+ } while (0)
+#endif

/*
* Management for journal control blocks: functions to create and
@@ -1517,11 +1545,10 @@ static int journal_load_superblock(journal_t *journal)
* superblock and initialize the journal_t object.
*/

-static journal_t *journal_init_common(struct block_device *bdev,
- struct block_device *fs_dev,
- unsigned long long start, int len, int blocksize)
+static journal_t *journal_init_common(struct block_device *bdev, struct block_device *fs_dev,
+ unsigned long long start, int len, int blocksize,
+ struct jbd2_lock_class_keys *keys)
{
- static struct lock_class_key jbd2_trans_commit_key;
journal_t *journal;
int err;
int n;
@@ -1547,20 +1574,20 @@ static journal_t *journal_init_common(struct block_device *bdev,
init_waitqueue_head(&journal->j_wait_updates);
init_waitqueue_head(&journal->j_wait_reserved);
init_waitqueue_head(&journal->j_fc_wait);
- mutex_init(&journal->j_abort_mutex);
- mutex_init(&journal->j_barrier);
- mutex_init(&journal->j_checkpoint_mutex);
- spin_lock_init(&journal->j_revoke_lock);
- spin_lock_init(&journal->j_list_lock);
- spin_lock_init(&journal->j_history_lock);
- rwlock_init(&journal->j_state_lock);
+ mutex_init_with_key(&journal->j_abort_mutex, &keys->j_abort_mutex);
+ mutex_init_with_key(&journal->j_barrier, &keys->j_barrier);
+ mutex_init_with_key(&journal->j_checkpoint_mutex, &keys->j_checkpoint_mutex);
+ spin_lock_init_with_key(&journal->j_revoke_lock, &keys->j_revoke_lock);
+ spin_lock_init_with_key(&journal->j_list_lock, &keys->j_list_lock);
+ spin_lock_init_with_key(&journal->j_history_lock, &keys->j_history_lock);
+ rwlock_init_with_key(&journal->j_state_lock, &keys->j_state_lock);

journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);
journal->j_min_batch_time = 0;
journal->j_max_batch_time = 15000; /* 15ms */
atomic_set(&journal->j_reserved_credits, 0);
- lockdep_init_map(&journal->j_trans_commit_map, "jbd2_handle",
- &jbd2_trans_commit_key, 0);
+ lockdep_init_map(&journal->j_trans_commit_map, keys->name,
+ &keys->jbd2_trans_commit_key, 0);

/* The journal is marked for error until we succeed with recovery! */
journal->j_flags = JBD2_ABORT;
@@ -1631,6 +1658,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
* @start: Block nr Start of journal.
* @len: Length of the journal in blocks.
* @blocksize: blocksize of journalling device
+ * @keys: Pointer to struct jbd2_lock_class_keys for lockdep annotation
*
* Returns: a newly created journal_t *
*
@@ -1638,13 +1666,13 @@ static journal_t *journal_init_common(struct block_device *bdev,
* range of blocks on an arbitrary block device.
*
*/
-journal_t *jbd2_journal_init_dev(struct block_device *bdev,
- struct block_device *fs_dev,
- unsigned long long start, int len, int blocksize)
+journal_t *jbd2_journal_init_dev(struct block_device *bdev, struct block_device *fs_dev,
+ unsigned long long start, int len, int blocksize,
+ struct jbd2_lock_class_keys *keys)
{
journal_t *journal;

- journal = journal_init_common(bdev, fs_dev, start, len, blocksize);
+ journal = journal_init_common(bdev, fs_dev, start, len, blocksize, keys);
if (IS_ERR(journal))
return ERR_CAST(journal);

@@ -1664,7 +1692,7 @@ journal_t *jbd2_journal_init_dev(struct block_device *bdev,
* the journal. The inode must exist already, must support bmap() and
* must have all data blocks preallocated.
*/
-journal_t *jbd2_journal_init_inode(struct inode *inode)
+journal_t *jbd2_journal_init_inode(struct inode *inode, struct jbd2_lock_class_keys *keys)
{
journal_t *journal;
sector_t blocknr;
@@ -1682,8 +1710,8 @@ journal_t *jbd2_journal_init_inode(struct inode *inode)
inode->i_sb->s_blocksize_bits, inode->i_sb->s_blocksize);

journal = journal_init_common(inode->i_sb->s_bdev, inode->i_sb->s_bdev,
- blocknr, inode->i_size >> inode->i_sb->s_blocksize_bits,
- inode->i_sb->s_blocksize);
+ blocknr, inode->i_size >> inode->i_sb->s_blocksize_bits,
+ inode->i_sb->s_blocksize, keys);
if (IS_ERR(journal))
return ERR_CAST(journal);

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 699c15db28a8..fc93a2ef5c2d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -60,6 +60,8 @@
#define CREATE_TRACE_POINTS
#include <trace/events/ext4.h>

+static struct jbd2_lock_class_keys jbd2_ext4_lock_class_keys = { .name = "jbd2_ext4_handle" };
+
static struct ext4_lazy_init *ext4_li_info;
static DEFINE_MUTEX(ext4_li_mtx);
static struct ratelimit_state ext4_mount_msg_ratelimit;
@@ -5851,7 +5853,7 @@ static journal_t *ext4_open_inode_journal(struct super_block *sb,
if (IS_ERR(journal_inode))
return ERR_CAST(journal_inode);

- journal = jbd2_journal_init_inode(journal_inode);
+ journal = jbd2_journal_init_inode(journal_inode, &jbd2_ext4_lock_class_keys);
if (IS_ERR(journal)) {
ext4_msg(sb, KERN_ERR, "Could not load journal inode");
iput(journal_inode);
@@ -5956,7 +5958,7 @@ static journal_t *ext4_open_dev_journal(struct super_block *sb,
return ERR_CAST(bdev_file);

journal = jbd2_journal_init_dev(file_bdev(bdev_file), sb->s_bdev, j_start,
- j_len, sb->s_blocksize);
+ j_len, sb->s_blocksize, &jbd2_ext4_lock_class_keys);
if (IS_ERR(journal)) {
ext4_msg(sb, KERN_ERR, "failed to create device journal");
errno = PTR_ERR(journal);
diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index e5f58ff2175f..e92746e3cb0b 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -43,6 +43,8 @@

DEFINE_SPINLOCK(trans_inc_lock);

+static struct jbd2_lock_class_keys jbd2_ocfs2_lock_class_keys = { .name = "jbd2_ocfs2_handle" };
+
#define ORPHAN_SCAN_SCHEDULE_TIMEOUT 300000

static int ocfs2_force_read_journal(struct inode *inode);
@@ -968,7 +970,7 @@ int ocfs2_journal_init(struct ocfs2_super *osb, int *dirty)
OCFS2_I(inode)->ip_clusters);

/* call the kernels journal init function now */
- j_journal = jbd2_journal_init_inode(inode);
+ j_journal = jbd2_journal_init_inode(inode, &jbd2_ocfs2_lock_class_keys);
if (IS_ERR(j_journal)) {
mlog(ML_ERROR, "Linux journal layer error\n");
status = PTR_ERR(j_journal);
@@ -1759,7 +1761,7 @@ static int ocfs2_replay_journal(struct ocfs2_super *osb,
goto done;
}

- journal = jbd2_journal_init_inode(inode);
+ journal = jbd2_journal_init_inode(inode, &jbd2_ocfs2_lock_class_keys);
if (IS_ERR(journal)) {
mlog(ML_ERROR, "Linux journal layer error\n");
status = PTR_ERR(journal);