knfsd: clean up nfsd filesystem interfaces

Several of the nfsd filesystem interfaces allow changes to parameters
that don't have any effect on a running nfsd service. They are only ever
checked when nfsd is started. This patch fixes it so that changes to
those procfiles return -EBUSY if nfsd is already running to make it
clear that changes on the fly don't work.

The patch should also close some relatively harmless races between
changing the info in those interfaces and starting nfsd, since these
variables are being moved under the protection of the nfsd_mutex.

Finally, the nfsv4recoverydir file always returns -EINVAL if read. This
patch fixes it to return the recoverydir path as expected.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 53 insertions, 13 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 049d2a9c771..2c2eb8796c1 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -509,7 +509,7 @@ out_free:
 	return rv;
 }
 
-static ssize_t write_versions(struct file *file, char *buf, size_t size)
+static ssize_t __write_versions(struct file *file, char *buf, size_t size)
 {
 	/*
 	 * Format:
@@ -572,6 +572,16 @@ static ssize_t write_versions(struct file *file, char *buf, size_t size)
 	return len;
 }
 
+static ssize_t write_versions(struct file *file, char *buf, size_t size)
+{
+	ssize_t rv;
+
+	mutex_lock(&nfsd_mutex);
+	rv = __write_versions(file, buf, size);
+	mutex_unlock(&nfsd_mutex);
+	return rv;
+}
+
 static ssize_t __write_ports(struct file *file, char *buf, size_t size)
 {
 	if (size == 0) {
@@ -675,6 +685,7 @@ static ssize_t __write_ports(struct file *file, char *buf, size_t size)
 static ssize_t write_ports(struct file *file, char *buf, size_t size)
 {
 	ssize_t rv;
+
 	mutex_lock(&nfsd_mutex);
 	rv = __write_ports(file, buf, size);
 	mutex_unlock(&nfsd_mutex);
@@ -714,16 +725,17 @@ static ssize_t write_maxblksize(struct file *file, char *buf, size_t size)
 #ifdef CONFIG_NFSD_V4
 extern time_t nfs4_leasetime(void);
 
-static ssize_t write_leasetime(struct file *file, char *buf, size_t size)
+static ssize_t __write_leasetime(struct file *file, char *buf, size_t size)
 {
 	/* if size > 10 seconds, call
 	 * nfs4_reset_lease() then write out the new lease (seconds) as reply
 	 */
 	char *mesg = buf;
-	int rv;
+	int rv, lease;
 
 	if (size > 0) {
-		int lease;
+		if (nfsd_serv)
+			return -EBUSY;
 		rv = get_int(&mesg, &lease);
 		if (rv)
 			return rv;
@@ -735,24 +747,52 @@ static ssize_t write_leasetime(struct file *file, char *buf, size_t size)
 	return strlen(buf);
 }
 
-static ssize_t write_recoverydir(struct file *file, char *buf, size_t size)
+static ssize_t write_leasetime(struct file *file, char *buf, size_t size)
+{
+	ssize_t rv;
+
+	mutex_lock(&nfsd_mutex);
+	rv = __write_leasetime(file, buf, size);
+	mutex_unlock(&nfsd_mutex);
+	return rv;
+}
+
+extern char *nfs4_recoverydir(void);
+
+static ssize_t __write_recoverydir(struct file *file, char *buf, size_t size)
 {
 	char *mesg = buf;
 	char *recdir;
 	int len, status;
 
-	if (size == 0 || size > PATH_MAX || buf[size-1] != '\n')
-		return -EINVAL;
-	buf[size-1] = 0;
+	if (size > 0) {
+		if (nfsd_serv)
+			return -EBUSY;
+		if (size > PATH_MAX || buf[size-1] != '\n')
+			return -EINVAL;
+		buf[size-1] = 0;
 
-	recdir = mesg;
-	len = qword_get(&mesg, recdir, size);
-	if (len <= 0)
-		return -EINVAL;
+		recdir = mesg;
+		len = qword_get(&mesg, recdir, size);
+		if (len <= 0)
+			return -EINVAL;
 
-	status = nfs4_reset_recoverydir(recdir);
+		status = nfs4_reset_recoverydir(recdir);
+	}
+	sprintf(buf, "%s\n", nfs4_recoverydir());
 	return strlen(buf);
 }
+
+static ssize_t write_recoverydir(struct file *file, char *buf, size_t size)
+{
+	ssize_t rv;
+
+	mutex_lock(&nfsd_mutex);
+	rv = __write_recoverydir(file, buf, size);
+	mutex_unlock(&nfsd_mutex);
+	return rv;
+}
+
 #endif
 
 /*----------------------------------------------------------------------------*/