Commit 85a4ffad authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
Browse files

sysfs: implement sysfs_open_dirent 



Implement sysfs_open_dirent which represents an open file (attribute)
sysfs_dirent.  A file sysfs_dirent with one or more open files have
one sysfs_dirent and all sysfs_buffers (one for each open instance)
are linked to it.

sysfs_open_dirent doesn't actually do anything yet but will be used to
off-load things which are specific for open file sysfs_dirent from it.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Acked-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent bc747f37

fs/sysfs/file.c

+108 −1
Original line number Diff line number Diff line
@@ -49,6 +49,22 @@ static struct sysfs_ops subsys_sysfs_ops = { 
	.store	= subsys_attr_store,

};



/*

 * There's one sysfs_buffer for each open file and one

 * sysfs_open_dirent for each sysfs_dirent with one or more open

 * files.

 *

 * filp->private_data points to sysfs_buffer and

 * sysfs_dirent->s_attr.open points to sysfs_open_dirent.  s_attr.open

 * is protected by sysfs_open_dirent_lock.

 */

static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED;



struct sysfs_open_dirent {

	atomic_t		refcnt;

	struct list_head	buffers; /* goes through sysfs_buffer.list */

};



struct sysfs_buffer {

	size_t			count;

	loff_t			pos;
@@ -57,6 +73,7 @@ struct sysfs_buffer { 
	struct mutex		mutex;

	int			needs_read_fill;

	int			event;

	struct list_head	list;

};



/**
@@ -237,6 +254,86 @@ sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t 
	return len;

}



/**

 *	sysfs_get_open_dirent - get or create sysfs_open_dirent

 *	@sd: target sysfs_dirent

 *	@buffer: sysfs_buffer for this instance of open

 *

 *	If @sd->s_attr.open exists, increment its reference count;

 *	otherwise, create one.  @buffer is chained to the buffers

 *	list.

 *

 *	LOCKING:

 *	Kernel thread context (may sleep).

 *

 *	RETURNS:

 *	0 on success, -errno on failure.

 */

static int sysfs_get_open_dirent(struct sysfs_dirent *sd,

				 struct sysfs_buffer *buffer)

{

	struct sysfs_open_dirent *od, *new_od = NULL;



 retry:

	spin_lock(&sysfs_open_dirent_lock);



	if (!sd->s_attr.open && new_od) {

		sd->s_attr.open = new_od;

		new_od = NULL;

	}



	od = sd->s_attr.open;

	if (od) {

		atomic_inc(&od->refcnt);

		list_add_tail(&buffer->list, &od->buffers);

	}



	spin_unlock(&sysfs_open_dirent_lock);



	if (od) {

		kfree(new_od);

		return 0;

	}



	/* not there, initialize a new one and retry */

	new_od = kmalloc(sizeof(*new_od), GFP_KERNEL);

	if (!new_od)

		return -ENOMEM;



	atomic_set(&new_od->refcnt, 0);

	INIT_LIST_HEAD(&new_od->buffers);

	goto retry;

}



/**

 *	sysfs_put_open_dirent - put sysfs_open_dirent

 *	@sd: target sysfs_dirent

 *	@buffer: associated sysfs_buffer

 *

 *	Put @sd->s_attr.open and unlink @buffer from the buffers list.

 *	If reference count reaches zero, disassociate and free it.

 *

 *	LOCKING:

 *	None.

 */

static void sysfs_put_open_dirent(struct sysfs_dirent *sd,

				  struct sysfs_buffer *buffer)

{

	struct sysfs_open_dirent *od = sd->s_attr.open;



	spin_lock(&sysfs_open_dirent_lock);



	list_del(&buffer->list);

	if (atomic_dec_and_test(&od->refcnt))

		sd->s_attr.open = NULL;

	else

		od = NULL;



	spin_unlock(&sysfs_open_dirent_lock);



	kfree(od);

}



static int sysfs_open_file(struct inode *inode, struct file *file)

{

	struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
@@ -298,10 +395,17 @@ static int sysfs_open_file(struct inode *inode, struct file *file) 
	buffer->ops = ops;

	file->private_data = buffer;



	/* make sure we have open dirent struct */

	error = sysfs_get_open_dirent(attr_sd, buffer);

	if (error)

		goto err_free;



	/* open succeeded, put active references */

	sysfs_put_active_two(attr_sd);

	return 0;



 err_free:

	kfree(buffer);

 err_out:

	sysfs_put_active_two(attr_sd);

	return error;
@@ -309,8 +413,11 @@ static int sysfs_open_file(struct inode *inode, struct file *file) 


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

{

	struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata;

	struct sysfs_buffer *buffer = filp->private_data;



	sysfs_put_open_dirent(sd, buffer);



	if (buffer->page)

		free_page((unsigned long)buffer->page);

	kfree(buffer);

fs/sysfs/sysfs.h

+3 −0
Original line number Diff line number Diff line 
struct sysfs_open_dirent;



/* type-specific structures for sysfs_dirent->s_* union members */

struct sysfs_elem_dir {

	struct kobject		*kobj;
@@ -11,6 +13,7 @@ struct sysfs_elem_symlink { 


struct sysfs_elem_attr {

	struct attribute	*attr;

	struct sysfs_open_dirent *open;

};



struct sysfs_elem_bin_attr {

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