[PATCH 2/4] pktcdvd: kill mutex_lock_nested() usage

From: Kent Overstreet <kent.overstreet@linux.dev>
To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	linux-fsdevel@vgerkernel.org
Cc: Kent Overstreet <kent.overstreet@linux.dev>,
	peterz@infradead.org, boqun.feng@gmail.com,
	linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 2/4] pktcdvd: kill mutex_lock_nested() usage
Date: Fri, 26 Jan 2024 21:01:06 -0500	[thread overview]
Message-ID: <20240127020111.487218-3-kent.overstreet@linux.dev> (raw)
In-Reply-To: <20240127020111.487218-1-kent.overstreet@linux.dev>

Unecessary, we're not actually taking nested locks of the same type.

Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 drivers/block/pktcdvd.c  |  8 ++++----
 fs/pipe.c                | 10 +---------
 include/linux/lockdep.h  |  3 +++
 kernel/locking/lockdep.c |  6 ++++++
 4 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index d56d972aadb3..2eb68a624fda 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -332,7 +332,7 @@ static ssize_t device_map_show(const struct class *c, const struct class_attribu
 {
 	int n = 0;
 	int idx;
-	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock(&ctl_mutex);
 	for (idx = 0; idx < MAX_WRITERS; idx++) {
 		struct pktcdvd_device *pd = pkt_devs[idx];
 		if (!pd)
@@ -2639,7 +2639,7 @@ static int pkt_setup_dev(dev_t dev, dev_t* pkt_dev)
 	struct pktcdvd_device *pd;
 	struct gendisk *disk;
 
-	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock(&ctl_mutex);
 
 	for (idx = 0; idx < MAX_WRITERS; idx++)
 		if (!pkt_devs[idx])
@@ -2729,7 +2729,7 @@ static int pkt_remove_dev(dev_t pkt_dev)
 	int idx;
 	int ret = 0;
 
-	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock(&ctl_mutex);
 
 	for (idx = 0; idx < MAX_WRITERS; idx++) {
 		pd = pkt_devs[idx];
@@ -2780,7 +2780,7 @@ static void pkt_get_status(struct pkt_ctrl_command *ctrl_cmd)
 {
 	struct pktcdvd_device *pd;
 
-	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock(&ctl_mutex);
 
 	pd = pkt_find_dev_from_minor(ctrl_cmd->dev_index);
 	if (pd) {
diff --git a/fs/pipe.c b/fs/pipe.c
index 50c8a8596b52..abe171566015 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -78,14 +78,6 @@ static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
 
 #define cmp_int(l, r)		((l > r) - (l < r))
 
-#ifdef CONFIG_PROVE_LOCKING
-static int pipe_lock_cmp_fn(const struct lockdep_map *a,
-			    const struct lockdep_map *b)
-{
-	return cmp_int((unsigned long) a, (unsigned long) b);
-}
-#endif
-
 void pipe_lock(struct pipe_inode_info *pipe)
 {
 	if (pipe->files)
@@ -824,7 +816,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
 		pipe->nr_accounted = pipe_bufs;
 		pipe->user = user;
 		mutex_init(&pipe->mutex);
-		lock_set_cmp_fn(&pipe->mutex, pipe_lock_cmp_fn, NULL);
+		lock_set_cmp_fn_ptr_order(&pipe->mutex);
 		return pipe;
 	}
 
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 08b0d1d9d78b..e0b121f96c80 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -391,6 +391,7 @@ extern int lockdep_is_held(const void *);
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_PROVE_LOCKING
+int lockdep_ptr_order_cmp_fn(const struct lockdep_map *, const struct lockdep_map *);
 void lockdep_set_lock_cmp_fn(struct lockdep_map *, lock_cmp_fn, lock_print_fn);
 
 #define lock_set_cmp_fn(lock, ...)	lockdep_set_lock_cmp_fn(&(lock)->dep_map, __VA_ARGS__)
@@ -398,6 +399,8 @@ void lockdep_set_lock_cmp_fn(struct lockdep_map *, lock_cmp_fn, lock_print_fn);
 #define lock_set_cmp_fn(lock, ...)	do { } while (0)
 #endif
 
+#define lock_set_cmp_fn_ptr_order(lock)	lock_set_cmp_fn(lock, lockdep_ptr_order_cmp_fn);
+
 enum xhlock_context_t {
 	XHLOCK_HARD,
 	XHLOCK_SOFT,
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 151bd3de5936..5630be7f5cb2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4919,6 +4919,12 @@ struct lock_class_key __lockdep_no_validate__;
 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
 
 #ifdef CONFIG_PROVE_LOCKING
+int lockdep_ptr_order_cmp_fn(const struct lockdep_map *a,
+			     const struct lockdep_map *b)
+{
+	return cmp_int((unsigned long) a, (unsigned long) b);
+}
+
 void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn,
 			     lock_print_fn print_fn)
 {
-- 
2.43.0

