sysfs: Fix binary file handling

From Manuel Estrada Sainz <ranty@debian.org>


>   - sysfs-bin-flexible-size.diff:
>       Make dynamically sized files possible.  And return the right
>       value on successful write.
>
>   - sysfs-bin-lost-dget.diff:
>       I was having trouble when calling request_firmware() from a work
>       queue, and after a little investigations it seams that this dget
>       got lost along the way. Adding it back fixed the issue.
>       Or am I causing a dentry leak now?

fs/sysfs/bin.c

@@ -30,10 +30,15 @@ read(struct file * file, char * userbuf, size_t count, loff_t * off)
 	loff_t offs = *off;
 	int ret;
 
-	if (offs > size)
-		return 0;
-	if (offs + count > size)
-		count = size - offs;
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
+
+	if (size) {
+		if (offs > size)
+			return 0;
+		if (offs + count > size)
+			count = size - offs;
+	}
 
 	ret = fill_read(dentry, buffer, offs, count);
 	if (ret < 0) 
@@ -41,7 +46,7 @@ read(struct file * file, char * userbuf, size_t count, loff_t * off)
 	count = ret;
 
 	ret = -EFAULT;
-	if (copy_to_user(userbuf, buffer + offs, count) != 0)
+	if (copy_to_user(userbuf, buffer, count) != 0)
 		goto Done;
 
 	*off = offs + count;
@@ -69,19 +74,23 @@ static ssize_t write(struct file * file, const char * userbuf,
 	loff_t offs = *off;
 	int ret;
 
-	if (offs > size)
-		return 0;
-	if (offs + count > size)
-		count = size - offs;
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
+	if (size) {
+		if (offs > size)
+			return 0;
+		if (offs + count > size)
+			count = size - offs;
+	}
 
 	ret = -EFAULT;
-	if (copy_from_user(buffer + offs, userbuf, count))
+	if (copy_from_user(buffer, userbuf, count))
 		goto Done;
 
 	count = flush_write(dentry, buffer, offs, count);
 	if (count > 0)
 		*off = offs + count;
-	ret = 0;
+	ret = count;
  Done:
 	return ret;
 }
@@ -102,7 +111,7 @@ static int open(struct inode * inode, struct file * file)
 		goto Done;
 
 	error = -ENOMEM;
-	file->private_data = kmalloc(attr->size, GFP_KERNEL);
+	file->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
 	if (!file->private_data)
 		goto Done;
 

fs/sysfs/inode.c

@@ -60,9 +60,10 @@ int sysfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
  Proceed:
 	if (init)
 		error = init(inode);
-	if (!error)
+	if (!error) {
 		d_instantiate(dentry, inode);
-	else
+		dget(dentry); /* Extra count - pin the dentry in core */
+	} else
 		iput(inode);
  Done:
 	return error;

include/linux/sysfs.h

@@ -23,6 +23,9 @@ struct bin_attribute {
 	ssize_t (*write)(struct kobject *, char *, loff_t, size_t);
 };
 
+int sysfs_create_bin_file(struct kobject * kobj, struct bin_attribute * attr);
+int sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr);
+
 struct sysfs_ops {
 	ssize_t	(*show)(struct kobject *, struct attribute *,char *);
 	ssize_t	(*store)(struct kobject *,struct attribute *,const char *, size_t);