/*
- * file.c - operations for regular (text) files.
+ * fs/sysfs/file.c - sysfs regular (text) file implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
*/
#include <linux/module.h>
.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;
+ atomic_t event;
+ wait_queue_head_t poll;
+ struct list_head buffers; /* goes through sysfs_buffer.list */
+};
+
struct sysfs_buffer {
size_t count;
loff_t pos;
struct mutex mutex;
int needs_read_fill;
int event;
+ struct list_head list;
};
/**
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
- buffer->event = atomic_read(&attr_sd->s_event);
+ buffer->event = atomic_read(&attr_sd->s_attr.open->event);
count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
sysfs_put_active_two(attr_sd);
- BUG_ON(count > (ssize_t)PAGE_SIZE);
+ /*
+ * The code works fine with PAGE_SIZE return but it's likely to
+ * indicate truncated result or overflow in normal use cases.
+ */
+ BUG_ON(count >= (ssize_t)PAGE_SIZE);
if (count >= 0) {
buffer->needs_read_fill = 0;
buffer->count = count;
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);
+ atomic_set(&new_od->event, 1);
+ init_waitqueue_head(&new_od->poll);
+ 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;
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);
{
struct sysfs_buffer * buffer = filp->private_data;
struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
- struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
+ struct sysfs_open_dirent *od = attr_sd->s_attr.open;
/* need parent for the kobj, grab both */
if (!sysfs_get_active_two(attr_sd))
goto trigger;
- poll_wait(filp, &kobj->poll, wait);
+ poll_wait(filp, &od->poll, wait);
sysfs_put_active_two(attr_sd);
- if (buffer->event != atomic_read(&attr_sd->s_event))
+ if (buffer->event != atomic_read(&od->event))
goto trigger;
return 0;
if (sd && attr)
sd = sysfs_find_dirent(sd, attr);
if (sd) {
- atomic_inc(&sd->s_event);
- wake_up_interruptible(&k->poll);
+ struct sysfs_open_dirent *od;
+
+ spin_lock(&sysfs_open_dirent_lock);
+
+ od = sd->s_attr.open;
+ if (od) {
+ atomic_inc(&od->event);
+ wake_up_interruptible(&od->poll);
+ }
+
+ spin_unlock(&sysfs_open_dirent_lock);
}
mutex_unlock(&sysfs_mutex);
/**
* sysfs_create_file - create an attribute file for an object.
* @kobj: object we're creating for.
- * @attr: atrribute descriptor.
+ * @attr: attribute descriptor.
*/
int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
projects / powerpc.git / blobdiff