The decision to free kernfs_open_node object in kernfs_put_open_node can
be taken based on whether kernfs_open_node->files list is empty or not. As
far as kernfs_drain_open_files is concerned it can't overlap with
kernfs_fops_open and hence can check for ->attr.open optimistically
(if ->attr.open is NULL) or under kernfs_open_file_mutex (if it needs to
traverse the ->files list.) Thus kernfs_drain_open_files can work w/o ref
counting involved kernfs_open_node as well.
So remove ->refcnt and modify the above mentioned users accordingly.
Suggested by: Al Viro <[email protected]>
Signed-off-by: Imran Khan <[email protected]>
---
fs/kernfs/file.c | 23 +++++++++--------------
1 file changed, 9 insertions(+), 14 deletions(-)
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 88423069407c..aea6968c979e 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -33,7 +33,6 @@ static DEFINE_SPINLOCK(kernfs_open_node_lock);
static DEFINE_MUTEX(kernfs_open_file_mutex);
struct kernfs_open_node {
- atomic_t refcnt;
atomic_t event;
wait_queue_head_t poll;
struct list_head files; /* goes through kernfs_open_file.list */
@@ -530,10 +529,8 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
}
on = kn->attr.open;
- if (on) {
- atomic_inc(&on->refcnt);
+ if (on)
list_add_tail(&of->list, &on->files);
- }
spin_unlock_irq(&kernfs_open_node_lock);
mutex_unlock(&kernfs_open_file_mutex);
@@ -548,7 +545,6 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
if (!new_on)
return -ENOMEM;
- atomic_set(&new_on->refcnt, 0);
atomic_set(&new_on->event, 1);
init_waitqueue_head(&new_on->poll);
INIT_LIST_HEAD(&new_on->files);
@@ -557,11 +553,12 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
/**
* kernfs_put_open_node - put kernfs_open_node
- * @kn: target kernfs_nodet
+ * @kn: target kernfs_node
* @of: associated kernfs_open_file
*
* Put @kn->attr.open and unlink @of from the files list. If
- * reference count reaches zero, disassociate and free it.
+ * list of associated open files becomes empty, disassociate and
+ * free kernfs_open_node.
*
* LOCKING:
* None.
@@ -578,7 +575,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
if (of)
list_del(&of->list);
- if (atomic_dec_and_test(&on->refcnt))
+ if (list_empty(&on->files))
kn->attr.open = NULL;
else
on = NULL;
@@ -768,15 +765,15 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
return;
- spin_lock_irq(&kernfs_open_node_lock);
on = kn->attr.open;
- if (on)
- atomic_inc(&on->refcnt);
- spin_unlock_irq(&kernfs_open_node_lock);
if (!on)
return;
mutex_lock(&kernfs_open_file_mutex);
+ if (!kn->attr.open) {
+ mutex_unlock(&kernfs_open_file_mutex);
+ return;
+ }
list_for_each_entry(of, &on->files, list) {
struct inode *inode = file_inode(of->file);
@@ -789,8 +786,6 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
}
mutex_unlock(&kernfs_open_file_mutex);
-
- kernfs_put_open_node(kn, NULL);
}
/*
--
2.30.2