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kernfs: Remove reference counting for kernfs_open_node.
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 <viro@zeniv.linux.org.uk> Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Link: https://lore.kernel.org/r/20220324103040.584491-2-imran.f.khan@oracle.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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parent
6423d29510
commit
bd900901b8
1 changed files with 9 additions and 14 deletions
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@ -33,7 +33,6 @@ static DEFINE_SPINLOCK(kernfs_open_node_lock);
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static DEFINE_MUTEX(kernfs_open_file_mutex);
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struct kernfs_open_node {
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atomic_t refcnt;
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atomic_t event;
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wait_queue_head_t poll;
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struct list_head files; /* goes through kernfs_open_file.list */
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@ -530,10 +529,8 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
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}
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on = kn->attr.open;
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if (on) {
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atomic_inc(&on->refcnt);
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if (on)
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list_add_tail(&of->list, &on->files);
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}
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spin_unlock_irq(&kernfs_open_node_lock);
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mutex_unlock(&kernfs_open_file_mutex);
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@ -548,7 +545,6 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
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if (!new_on)
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return -ENOMEM;
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atomic_set(&new_on->refcnt, 0);
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atomic_set(&new_on->event, 1);
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init_waitqueue_head(&new_on->poll);
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INIT_LIST_HEAD(&new_on->files);
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@ -557,11 +553,12 @@ static int kernfs_get_open_node(struct kernfs_node *kn,
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/**
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* kernfs_put_open_node - put kernfs_open_node
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* @kn: target kernfs_nodet
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* @kn: target kernfs_node
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* @of: associated kernfs_open_file
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*
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* Put @kn->attr.open and unlink @of from the files list. If
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* reference count reaches zero, disassociate and free it.
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* list of associated open files becomes empty, disassociate and
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* free kernfs_open_node.
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*
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* LOCKING:
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* None.
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@ -578,7 +575,7 @@ static void kernfs_put_open_node(struct kernfs_node *kn,
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if (of)
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list_del(&of->list);
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if (atomic_dec_and_test(&on->refcnt))
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if (list_empty(&on->files))
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kn->attr.open = NULL;
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else
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on = NULL;
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@ -768,15 +765,15 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
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if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
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return;
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spin_lock_irq(&kernfs_open_node_lock);
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on = kn->attr.open;
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if (on)
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atomic_inc(&on->refcnt);
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spin_unlock_irq(&kernfs_open_node_lock);
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if (!on)
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return;
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mutex_lock(&kernfs_open_file_mutex);
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if (!kn->attr.open) {
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mutex_unlock(&kernfs_open_file_mutex);
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return;
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}
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list_for_each_entry(of, &on->files, list) {
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struct inode *inode = file_inode(of->file);
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@ -789,8 +786,6 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
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}
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mutex_unlock(&kernfs_open_file_mutex);
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kernfs_put_open_node(kn, NULL);
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}
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/*
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