diff --git a/src/mon/FSCommands.cc b/src/mon/FSCommands.cc
index d1ecabb1499..b0ffd4c34a4 100644
--- a/src/mon/FSCommands.cc
+++ b/src/mon/FSCommands.cc
@@ -27,12 +27,9 @@ using std::hex;
 using std::list;
 using std::map;
 using std::make_pair;
-using std::ostream;
-using std::ostringstream;
 using std::pair;
 using std::set;
 using std::string;
-using std::stringstream;
 using std::to_string;
 using std::vector;
 
@@ -60,7 +57,7 @@ class FlagSetHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     string flag_name;
     cmd_getval(cmdmap, "flag_name", flag_name);
@@ -101,7 +98,7 @@ class FailHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream& ss) override
+      std::ostream& ss) override
   {
     if (!mon->osdmon()->is_writeable()) {
       // not allowed to write yet, so retry when we can
@@ -158,7 +155,7 @@ class FsNewHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     ceph_assert(m_paxos->is_plugged());
 
@@ -324,7 +321,7 @@ public:
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     std::string fs_name;
     if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
@@ -684,7 +681,7 @@ class RequiredClientFeaturesHandler : public FileSystemCommandHandler
 	FSMap &fsmap,
 	MonOpRequestRef op,
 	const cmdmap_t& cmdmap,
-	std::stringstream &ss) override
+	std::ostream &ss) override
     {
       std::string fs_name;
       if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
@@ -776,7 +773,7 @@ class AddDataPoolHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     ceph_assert(m_paxos->is_plugged());
 
@@ -850,7 +847,7 @@ class SetDefaultHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     std::string fs_name;
     cmd_getval(cmdmap, "fs_name", fs_name);
@@ -877,7 +874,7 @@ class RemoveFilesystemHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     /* We may need to blocklist ranks. */
     if (!mon->osdmon()->is_writeable()) {
@@ -951,7 +948,7 @@ class ResetFilesystemHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     string fs_name;
     cmd_getval(cmdmap, "fs_name", fs_name);
@@ -1001,7 +998,7 @@ class RenameFilesystemHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     ceph_assert(m_paxos->is_plugged());
 
@@ -1090,7 +1087,7 @@ class RemoveDataPoolHandler : public FileSystemCommandHandler
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     string poolname;
     cmd_getval(cmdmap, "pool", poolname);
@@ -1165,7 +1162,7 @@ class AliasHandler : public T
       FSMap& fsmap,
       MonOpRequestRef op,
       const cmdmap_t& cmdmap,
-      std::stringstream &ss) override
+      std::ostream &ss) override
   {
     return T::handle(mon, fsmap, op, cmdmap, ss);
   }
@@ -1180,7 +1177,7 @@ public:
 
   int handle(Monitor *mon,
              FSMap &fsmap, MonOpRequestRef op,
-             const cmdmap_t& cmdmap, std::stringstream &ss) override {
+             const cmdmap_t& cmdmap, std::ostream &ss) override {
     std::string fs_name;
     if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
       ss << "Missing filesystem name";
@@ -1215,7 +1212,7 @@ public:
 
   int handle(Monitor *mon,
              FSMap &fsmap, MonOpRequestRef op,
-             const cmdmap_t& cmdmap, std::stringstream &ss) override {
+             const cmdmap_t& cmdmap, std::ostream &ss) override {
     std::string fs_name;
     if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
       ss << "Missing filesystem name";
@@ -1262,7 +1259,7 @@ public:
   }
 
   bool peer_add(FSMap &fsmap, Filesystem::const_ref &&fs,
-                const cmdmap_t &cmdmap, std::stringstream &ss) {
+                const cmdmap_t &cmdmap, std::ostream &ss) {
     string peer_uuid;
     string remote_spec;
     string remote_fs_name;
@@ -1297,7 +1294,7 @@ public:
 
   int handle(Monitor *mon,
              FSMap &fsmap, MonOpRequestRef op,
-             const cmdmap_t& cmdmap, std::stringstream &ss) override {
+             const cmdmap_t& cmdmap, std::ostream &ss) override {
     std::string fs_name;
     if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
       ss << "Missing filesystem name";
@@ -1332,7 +1329,7 @@ public:
   {}
 
   bool peer_remove(FSMap &fsmap, Filesystem::const_ref &&fs,
-                   const cmdmap_t &cmdmap, std::stringstream &ss) {
+                   const cmdmap_t &cmdmap, std::ostream &ss) {
     string peer_uuid;
     cmd_getval(cmdmap, "uuid", peer_uuid);
 
@@ -1350,7 +1347,7 @@ public:
 
   int handle(Monitor *mon,
              FSMap &fsmap, MonOpRequestRef op,
-             const cmdmap_t& cmdmap, std::stringstream &ss) override {
+             const cmdmap_t& cmdmap, std::ostream &ss) override {
     std::string fs_name;
     if (!cmd_getval(cmdmap, "fs_name", fs_name) || fs_name.empty()) {
       ss << "Missing filesystem name";
@@ -1409,7 +1406,7 @@ int FileSystemCommandHandler::_check_pool(
     const int64_t pool_id,
     int type,
     bool force,
-    std::stringstream *ss) const
+    std::ostream *ss) const
 {
   ceph_assert(ss != NULL);
 
@@ -1479,7 +1476,7 @@ int FileSystemCommandHandler::_check_pool(
 
 int FileSystemCommandHandler::is_op_allowed(
     const MonOpRequestRef& op, const FSMap& fsmap, const cmdmap_t& cmdmap,
-    std::stringstream &ss) const
+    std::ostream &ss) const
 {
     string fs_name;
     cmd_getval(cmdmap, "fs_name", fs_name);
diff --git a/src/mon/FSCommands.h b/src/mon/FSCommands.h
index 726ff281a1b..4b59225f954 100644
--- a/src/mon/FSCommands.h
+++ b/src/mon/FSCommands.h
@@ -23,7 +23,7 @@
 #include "mds/FSMap.h"
 
 #include <string>
-#include <sstream>
+#include <ostream>
 
 class FileSystemCommandHandler : protected CommandHandler
 {
@@ -38,7 +38,7 @@ protected:
   /**
    * Return 0 if the pool is suitable for use with CephFS, or
    * in case of errors return a negative error code, and populate
-   * the passed stringstream with an explanation.
+   * the passed ostream with an explanation.
    *
    * @param metadata whether the pool will be for metadata (stricter checks)
    */
@@ -47,7 +47,7 @@ protected:
       const int64_t pool_id,
       int type,
       bool force,
-      std::stringstream *ss) const;
+      std::ostream *ss) const;
 
   virtual std::string const &get_prefix() const {return prefix;}
 
@@ -60,10 +60,10 @@ public:
   {}
 
   int is_op_allowed(const MonOpRequestRef& op, const FSMap& fsmap,
-		    const cmdmap_t& cmdmap, std::stringstream &ss) const;
+		    const cmdmap_t& cmdmap, std::ostream &ss) const;
 
   int can_handle(std::string const &prefix_, MonOpRequestRef& op, FSMap& fsmap,
-	         const cmdmap_t& cmdmap, std::stringstream &ss) const
+	         const cmdmap_t& cmdmap, std::ostream &ss) const
   {
     if (get_prefix() != prefix_) {
       return 0;
@@ -87,7 +87,7 @@ public:
     FSMap &fsmap,
     MonOpRequestRef op,
     const cmdmap_t& cmdmap,
-    std::stringstream &ss) = 0;
+    std::ostream &ss) = 0;
 };
 
 #endif