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From:   Imran Khan <imran.f.khan@oracle.com>
To:     tj@kernel.org, gregkh@linuxfoundation.org
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH v6 2/7] kernfs: Replace global kernfs_open_file_mutex with hashed mutexes.
Date:   Mon, 14 Feb 2022 23:03:17 +1100
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Remove global kernfs_open_file_mutex, using hashed mutex and corresponding
interface introduced in previous patch.

Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
---
 fs/kernfs/file.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 9414a7a60a9f4..295fe67950346 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -19,18 +19,13 @@
 #include "kernfs-internal.h"
 
 /*
- * There's one kernfs_open_file for each open file and one kernfs_open_node
- * for each kernfs_node with one or more open files.
- *
  * kernfs_node->attr.open points to kernfs_open_node.  attr.open is
  * protected by kernfs_open_node_lock.
  *
  * filp->private_data points to seq_file whose ->private points to
- * kernfs_open_file.  kernfs_open_files are chained at
- * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
+ * kernfs_open_file.
  */
 static DEFINE_SPINLOCK(kernfs_open_node_lock);
-static DEFINE_MUTEX(kernfs_open_file_mutex);
 
 struct kernfs_open_node {
 	atomic_t		refcnt;
@@ -524,9 +519,10 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
 				struct kernfs_open_file *of)
 {
 	struct kernfs_open_node *on, *new_on = NULL;
+	struct mutex *mutex = NULL;
 
  retry:
-	mutex_lock(&kernfs_open_file_mutex);
+	mutex = kernfs_open_file_mutex_lock(kn);
 	spin_lock_irq(&kernfs_open_node_lock);
 
 	if (!kn->attr.open && new_on) {
@@ -541,7 +537,7 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
 	}
 
 	spin_unlock_irq(&kernfs_open_node_lock);
-	mutex_unlock(&kernfs_open_file_mutex);
+	mutex_unlock(mutex);
 
 	if (on) {
 		kfree(new_on);
@@ -575,9 +571,10 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
 				 struct kernfs_open_file *of)
 {
 	struct kernfs_open_node *on = kn->attr.open;
+	struct mutex *mutex = NULL;
 	unsigned long flags;
 
-	mutex_lock(&kernfs_open_file_mutex);
+	mutex = kernfs_open_file_mutex_lock(kn);
 	spin_lock_irqsave(&kernfs_open_node_lock, flags);
 
 	if (of)
@@ -589,7 +586,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
 		on = NULL;
 
 	spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
-	mutex_unlock(&kernfs_open_file_mutex);
+	mutex_unlock(mutex);
 
 	kfree(on);
 }
@@ -729,11 +726,11 @@ static void kernfs_release_file(struct kernfs_node *kn,
 	/*
 	 * @of is guaranteed to have no other file operations in flight and
 	 * we just want to synchronize release and drain paths.
-	 * @kernfs_open_file_mutex is enough.  @of->mutex can't be used
+	 * @open_file_mutex is enough.  @of->mutex can't be used
 	 * here because drain path may be called from places which can
 	 * cause circular dependency.
 	 */
-	lockdep_assert_held(&kernfs_open_file_mutex);
+	lockdep_assert_held(kernfs_open_file_mutex_ptr(kn));
 
 	if (!of->released) {
 		/*
@@ -750,11 +747,12 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 {
 	struct kernfs_node *kn = inode->i_private;
 	struct kernfs_open_file *of = kernfs_of(filp);
+	struct mutex *lock = NULL;
 
 	if (kn->flags & KERNFS_HAS_RELEASE) {
-		mutex_lock(&kernfs_open_file_mutex);
+		lock = kernfs_open_file_mutex_lock(kn);
 		kernfs_release_file(kn, of);
-		mutex_unlock(&kernfs_open_file_mutex);
+		mutex_unlock(lock);
 	}
 
 	kernfs_put_open_node(kn, of);
@@ -769,6 +767,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
 {
 	struct kernfs_open_node *on;
 	struct kernfs_open_file *of;
+	struct mutex *mutex = NULL;
 
 	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
 		return;
@@ -781,7 +780,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
 	if (!on)
 		return;
 
-	mutex_lock(&kernfs_open_file_mutex);
+	mutex = kernfs_open_file_mutex_lock(kn);
 
 	list_for_each_entry(of, &on->files, list) {
 		struct inode *inode = file_inode(of->file);
@@ -793,7 +792,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
 			kernfs_release_file(kn, of);
 	}
 
-	mutex_unlock(&kernfs_open_file_mutex);
+	mutex_unlock(mutex);
 
 	kernfs_put_open_node(kn, NULL);
 }
-- 
2.30.2