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Commit 0e67db2f authored by Tejun Heo's avatar Tejun Heo
Browse files

kernfs: add kernfs_ops->open/release() callbacks 



Add ->open/release() methods to kernfs_ops.  ->open() is called when
the file is opened and ->release() when the file is either released or
severed.  These callbacks can be used, for example, to manage
persistent caching objects over multiple seq_file iterations.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: default avatarAcked-by: Zefan Li <lizefan@huawei.com>
parent a1d82aff

fs/kernfs/dir.c

+1 −1
Original line number Diff line number Diff line
@@ -468,7 +468,7 @@ static void kernfs_drain(struct kernfs_node *kn) 
		rwsem_release(&kn->dep_map, 1, _RET_IP_);

	}



	kernfs_unmap_bin_file(kn);

	kernfs_drain_open_files(kn);



	mutex_lock(&kernfs_mutex);

}

fs/kernfs/file.c

+45 −6
Original line number Diff line number Diff line
@@ -708,7 +708,8 @@ static int kernfs_fop_open(struct inode *inode, struct file *file) 
	if (error)

		goto err_free;



	((struct seq_file *)file->private_data)->private = of;

	of->seq_file = file->private_data;

	of->seq_file->private = of;



	/* seq_file clears PWRITE unconditionally, restore it if WRITE */

	if (file->f_mode & FMODE_WRITE)
@@ -717,13 +718,22 @@ static int kernfs_fop_open(struct inode *inode, struct file *file) 
	/* make sure we have open node struct */

	error = kernfs_get_open_node(kn, of);

	if (error)

		goto err_close;

		goto err_seq_release;



	if (ops->open) {

		/* nobody has access to @of yet, skip @of->mutex */

		error = ops->open(of);

		if (error)

			goto err_put_node;

	}



	/* open succeeded, put active references */

	kernfs_put_active(kn);

	return 0;



err_close:

err_put_node:

	kernfs_put_open_node(kn, of);

err_seq_release:

	seq_release(inode, file);

err_free:

	kfree(of->prealloc_buf);
@@ -733,11 +743,32 @@ static int kernfs_fop_open(struct inode *inode, struct file *file) 
	return error;

}



/* used from release/drain to ensure that ->release() is called exactly once */

static void kernfs_release_file(struct kernfs_node *kn,

				struct kernfs_open_file *of)

{

	if (!(kn->flags & KERNFS_HAS_RELEASE))

		return;



	mutex_lock(&of->mutex);

	if (!of->released) {

		/*

		 * A file is never detached without being released and we

		 * need to be able to release files which are deactivated

		 * and being drained.  Don't use kernfs_ops().

		 */

		kn->attr.ops->release(of);

		of->released = true;

	}

	mutex_unlock(&of->mutex);

}



static int kernfs_fop_release(struct inode *inode, struct file *filp)

{

	struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;

	struct kernfs_open_file *of = kernfs_of(filp);



	kernfs_release_file(kn, of);

	kernfs_put_open_node(kn, of);

	seq_release(inode, filp);

	kfree(of->prealloc_buf);
@@ -746,12 +777,12 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp) 
	return 0;

}



void kernfs_unmap_bin_file(struct kernfs_node *kn)

void kernfs_drain_open_files(struct kernfs_node *kn)

{

	struct kernfs_open_node *on;

	struct kernfs_open_file *of;



	if (!(kn->flags & KERNFS_HAS_MMAP))

	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))

		return;



	spin_lock_irq(&kernfs_open_node_lock);
@@ -763,10 +794,16 @@ void kernfs_unmap_bin_file(struct kernfs_node *kn) 
		return;



	mutex_lock(&kernfs_open_file_mutex);



	list_for_each_entry(of, &on->files, list) {

		struct inode *inode = file_inode(of->file);



		if (kn->flags & KERNFS_HAS_MMAP)

			unmap_mapping_range(inode->i_mapping, 0, 0, 1);



		kernfs_release_file(kn, of);

	}



	mutex_unlock(&kernfs_open_file_mutex);



	kernfs_put_open_node(kn, NULL);
@@ -965,6 +1002,8 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent, 
		kn->flags |= KERNFS_HAS_SEQ_SHOW;

	if (ops->mmap)

		kn->flags |= KERNFS_HAS_MMAP;

	if (ops->release)

		kn->flags |= KERNFS_HAS_RELEASE;



	rc = kernfs_add_one(kn);

	if (rc) {

fs/kernfs/kernfs-internal.h

+1 −1
Original line number Diff line number Diff line
@@ -104,7 +104,7 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent, 
 */

extern const struct file_operations kernfs_file_fops;



void kernfs_unmap_bin_file(struct kernfs_node *kn);

void kernfs_drain_open_files(struct kernfs_node *kn);



/*

 * symlink.c

include/linux/kernfs.h

+10 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ enum kernfs_node_flag { 
	KERNFS_SUICIDAL		= 0x0400,

	KERNFS_SUICIDED		= 0x0800,

	KERNFS_EMPTY_DIR	= 0x1000,

	KERNFS_HAS_RELEASE	= 0x2000,

};



/* @flags for kernfs_create_root() */
@@ -175,6 +176,7 @@ struct kernfs_open_file { 
	/* published fields */

	struct kernfs_node	*kn;

	struct file		*file;

	struct seq_file		*seq_file;

	void			*priv;



	/* private fields, do not use outside kernfs proper */
@@ -186,10 +188,18 @@ struct kernfs_open_file { 


	size_t			atomic_write_len;

	bool			mmapped:1;

	bool			released:1;

	const struct vm_operations_struct *vm_ops;

};



struct kernfs_ops {

	/*

	 * Optional open/release methods.  Both are called with

	 * @of->seq_file populated.

	 */

	int (*open)(struct kernfs_open_file *of);

	void (*release)(struct kernfs_open_file *of);



	/*

	 * Read is handled by either seq_file or raw_read().

	 *