This patch buffers writes to sysfs files and flushes them to the kobject
owner when the file is closed.
Generated from 2.6.11-rc1.
Signed-off-by: Mitch Williams <[EMAIL PROTECTED]>
diff -uprN -X dontdiff linux-2.6.11-clean/fs/sysfs/file.c
linux-2.6.11/fs/sysfs/file.c
--- linux-2.6.11-clean/fs/sysfs/file.c 2004-12-24 13:33:50.000000000 -0800
+++ linux-2.6.11/fs/sysfs/file.c 2005-01-21 13:09:21.000000000 -0800
@@ -62,6 +62,7 @@ struct sysfs_buffer {
struct sysfs_ops * ops;
struct semaphore sem;
int read_filled;
+ int needs_write_flush;
};
@@ -178,7 +178,8 @@ out:
*/
static int
-fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf,
size_t count)
+fill_write_buffer(struct sysfs_buffer *buffer, const char __user * buf,
+ size_t count, size_t pos)
{
int error;
@@ -187,10 +189,11 @@ fill_write_buffer(struct sysfs_buffer *
if (!buffer->page)
return -ENOMEM;
- if (count >= PAGE_SIZE)
- count = PAGE_SIZE - 1;
+ if (count + pos > PAGE_SIZE)
+ count = (PAGE_SIZE - 1) - pos;
error = copy_from_user(buffer->page,buf,count);
- buffer->needs_read_fill = 1;
+ buffer->needs_write_flush = 1;
+ buffer->count = pos + count;
return error ? -EFAULT : count;
}
@@ -206,13 +209,13 @@ fill_write_buffer(struct sysfs_buffer *
*/
static int
-flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer,
size_t count)
+flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
struct attribute * attr = to_attr(dentry);
struct kobject * kobj = to_kobj(dentry->d_parent);
struct sysfs_ops * ops = buffer->ops;
- return ops->store(kobj,attr,buffer->page,count);
+ return ops->store(kobj,attr, buffer->page, buffer->count);
}
@@ -225,12 +228,9 @@ flush_write_buffer(struct dentry * dentr
*
* Similar to sysfs_read_file(), though working in the opposite direction.
* We allocate and fill the data from the user in fill_write_buffer(),
- * then push it to the kobject in flush_write_buffer().
- * There is no easy way for us to know if userspace is only doing a partial
- * write, so we don't support them. We expect the entire buffer to come
- * on the first write.
- * Hint: if you're writing a value, first read the file, modify only the
- * the value you're changing, then write entire buffer back.
+ * but don't push it to the kobject until the file is closed.
+ * This allows for buffered writes, but unfortunately also hides error
+ * codes returned individual store functions until close time.
*/
static ssize_t
@@ -238,10 +238,10 @@ sysfs_write_file(struct file *file, cons
{
struct sysfs_buffer * buffer = file->private_data;
+ if (*ppos >= PAGE_SIZE)
+ return -ENOSPC;
down(&buffer->sem);
- count = fill_write_buffer(buffer,buf,count);
- if (count > 0)
- count = flush_write_buffer(file->f_dentry,buffer,count);
+ count = fill_write_buffer(buffer, buf, count, *ppos);
if (count > 0)
*ppos += count;
up(&buffer->sem);
@@ -337,6 +337,17 @@ static int sysfs_release(struct inode *
struct attribute * attr = to_attr(filp->f_dentry);
struct module * owner = attr->owner;
struct sysfs_buffer * buffer = filp->private_data;
+ int ret;
+
+ /* If data has been written to the file, then flush it
+ * back to the kobject's store function here.
+ */
+ if (buffer && kobj) {
+ down(&buffer->sem);
+ if (buffer->needs_write_flush)
+ ret = flush_write_buffer(filp->f_dentry, buffer);
+ up(&buffer->sem);
+ }
if (kobj)
kobject_put(kobj);
@@ -348,7 +352,10 @@ static int sysfs_release(struct inode *
free_page((unsigned long)buffer->page);
kfree(buffer);
}
- return 0;
+ /* If flush_write_buffer returned an error, pass it up.
+ * Otherwise, return success.
+ */
+ return (ret < 0 ? ret : 0);
}
struct file_operations sysfs_file_operations = {
-
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