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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: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Tejun Heo 2007-09-20 16:05:12 +09:00 committed by Greg Kroah-Hartman
parent bc747f37a0
commit 85a4ffad3d
2 changed files with 111 additions and 1 deletions
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109
fs/sysfs/file.c
View File

@ -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;
@ -298,19 +395,29 @@ 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;
}
static int sysfs_release(struct inode * inode, struct file * filp)
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);

3
fs/sysfs/sysfs.h
View File

@ -1,3 +1,5 @@
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 {