NFSD: Add a custom file operations structure for fault injection

Controlling the read and write functions allows me to add in "forget
client w.x.y.z", since we won't be limited to reading and writing only
u64 values.
Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/fault_inject.c

@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/debugfs.h>
 #include <linux/module.h>
+#include <asm/uaccess.h>
 
 #include "state.h"
 
@@ -48,10 +49,9 @@ static struct nfsd_fault_inject_op inject_ops[] = {
 static long int NUM_INJECT_OPS = sizeof(inject_ops) / sizeof(struct nfsd_fault_inject_op);
 static struct dentry *debug_dir;
 
-static int nfsd_inject_set(void *op_ptr, u64 val)
+static void nfsd_inject_set(struct nfsd_fault_inject_op *op, u64 val)
 {
 	u64 count = 0;
-	struct nfsd_fault_inject_op *op = op_ptr;
 
 	if (val == 0)
 		printk(KERN_INFO "NFSD Fault Injection: %s (all)", op->file);
@@ -62,19 +62,61 @@ static int nfsd_inject_set(void *op_ptr, u64 val)
 	count = nfsd_for_n_state(val, op->forget);
 	nfs4_unlock_state();
 	printk(KERN_INFO "NFSD: %s: found %llu", op->file, count);
-	return 0;
 }
 
-static int nfsd_inject_get(void *op_ptr, u64 *val)
+static void nfsd_inject_get(struct nfsd_fault_inject_op *op, u64 *val)
 {
-	struct nfsd_fault_inject_op *op = op_ptr;
 	nfs4_lock_state();
 	*val = nfsd_for_n_state(0, op->print);
 	nfs4_unlock_state();
-	return 0;
 }
 
-DEFINE_SIMPLE_ATTRIBUTE(fops_nfsd, nfsd_inject_get, nfsd_inject_set, "%llu\n");
+static ssize_t fault_inject_read(struct file *file, char __user *buf,
+				 size_t len, loff_t *ppos)
+{
+	static u64 val;
+	char read_buf[25];
+	size_t size, ret;
+	loff_t pos = *ppos;
+
+	if (!pos)
+		nfsd_inject_get(file->f_dentry->d_inode->i_private, &val);
+	size = scnprintf(read_buf, sizeof(read_buf), "%llu\n", val);
+
+	if (pos < 0)
+		return -EINVAL;
+	if (pos >= size || !len)
+		return 0;
+	if (len > size - pos)
+		len = size - pos;
+	ret = copy_to_user(buf, read_buf + pos, len);
+	if (ret == len)
+		return -EFAULT;
+	len -= ret;
+	*ppos = pos + len;
+	return len;
+}
+
+static ssize_t fault_inject_write(struct file *file, const char __user *buf,
+				  size_t len, loff_t *ppos)
+{
+	char write_buf[24];
+	size_t size = min(sizeof(write_buf), len) - 1;
+	u64 val;
+
+	if (copy_from_user(write_buf, buf, size))
+		return -EFAULT;
+
+	val = simple_strtoll(write_buf, NULL, 0);
+	nfsd_inject_set(file->f_dentry->d_inode->i_private, val);
+	return len; /* on success, claim we got the whole input */
+}
+
+static const struct file_operations fops_nfsd = {
+	.owner   = THIS_MODULE,
+	.read    = fault_inject_read,
+	.write   = fault_inject_write,
+};
 
 void nfsd_fault_inject_cleanup(void)
 {