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Subject[RESEND PATCH v7 1/8] kernfs: Introduce interface to access global kernfs_open_file_mutex.
Date
This allows to change underlying mutex locking, without needing to change
the users of the lock. For example next patch modifies this interface to
use hashed mutexes in place of a single global kernfs_open_file_mutex.

Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
---
fs/kernfs/file.c | 26 +++++++++++++++-----------
fs/kernfs/kernfs-internal.h | 18 ++++++++++++++++++
2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 7aefaca876a0..99793c32abc3 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -30,7 +30,7 @@
* kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
*/
static DEFINE_SPINLOCK(kernfs_open_node_lock);
-static DEFINE_MUTEX(kernfs_open_file_mutex);
+DEFINE_MUTEX(kernfs_open_file_mutex);

struct kernfs_open_node {
atomic_t refcnt;
@@ -519,9 +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) {
@@ -536,7 +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);
@@ -570,9 +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)
@@ -584,7 +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);
}
@@ -724,11 +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) {
/*
@@ -745,11 +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);
@@ -764,6 +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;
@@ -776,7 +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);
@@ -788,7 +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);
}
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index eeaa779b929c..df00a5f5a367 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -164,4 +164,22 @@ void kernfs_drain_open_files(struct kernfs_node *kn);
*/
extern const struct inode_operations kernfs_symlink_iops;

+extern struct mutex kernfs_open_file_mutex;
+
+static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn)
+{
+ return &kernfs_open_file_mutex;
+}
+
+static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn)
+{
+ struct mutex *lock;
+
+ lock = kernfs_open_file_mutex_ptr(kn);
+
+ mutex_lock(lock);
+
+ return lock;
+}
+
#endif /* __KERNFS_INTERNAL_H */
--
2.30.2
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