ref counting for nfs41_root

very similar to the issue with nfs41_open_state, an abandoned upcall could outlive its mount. to prevent their nfs41_root from being freed, upcalls need to hold a reference until they're finished. this also keeps all of its clients/sessions/rpc connections alive

Signed-off-by: Casey Bodley <cbodley@citi.umich.edu>

daemon/getattr.c

@@ -69,6 +69,7 @@ static int parse_getattr(unsigned char *buffer, uint32_t length, nfs41_upcall *u
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(args->state));
     if (status) goto out;
     upcall_open_state_ref(upcall, args->state);

daemon/lock.c

@@ -97,6 +97,7 @@ static int parse_lock(unsigned char *buffer, uint32_t length, nfs41_upcall *upca
     upcall_open_state_ref(upcall, args->state);
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->offset, sizeof(LONGLONG));
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->length, sizeof(LONGLONG));
@@ -185,6 +186,7 @@ static int parse_unlock(unsigned char *buffer, uint32_t length, nfs41_upcall *up
     upcall_open_state_ref(upcall, args->state);
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->count, sizeof(ULONG));
     if (status) goto out;
 

daemon/mount.c

@@ -100,7 +100,7 @@ out:
     return status;
 
 out_err:
-    nfs41_root_free(root);
+    nfs41_root_deref(root);
     goto out;
 }
 
@@ -136,7 +136,8 @@ static int handle_unmount(nfs41_upcall *upcall)
 {
     int status = NO_ERROR;
     unmount_upcall_args *args = &upcall->args.unmount;
-    nfs41_root_free(args->root);
+    /* release the original reference from nfs41_root_create() */
+    nfs41_root_deref(args->root);
     return status;
 }
 

daemon/namespace.c

@@ -57,6 +57,7 @@ int nfs41_root_create(
     root->wsize = wsize;
     root->rsize = rsize;
     InitializeCriticalSection(&root->lock);
+    root->ref_count = 1;
 
     /* generate a unique client_owner */
     status = nfs41_client_owner(name, &root->client_owner);
@@ -71,7 +72,7 @@ out:
     return status;
 }
 
-void nfs41_root_free(
+static void root_free(
     IN nfs41_root *root)
 {
     struct list_entry *entry, *tmp;
@@ -86,6 +87,25 @@ void nfs41_root_free(
     dprintf(NSLVL, "<-- nfs41_root_free()\n");
 }
 
+void nfs41_root_ref(
+    IN nfs41_root *root)
+{
+    const LONG count = InterlockedIncrement(&root->ref_count);
+
+    dprintf(2, "nfs41_root_ref() count %d\n", count);
+}
+
+void nfs41_root_deref(
+    IN nfs41_root *root)
+{
+    const LONG count = InterlockedDecrement(&root->ref_count);
+
+    dprintf(2, "nfs41_root_deref() count %d\n", count);
+    if (count == 0)
+        root_free(root);
+}
+
+
 /* root_client_find_addrs() */
 struct cl_addr_info {
     const multi_addr4       *addrs;

daemon/nfs41.h

@@ -168,12 +168,18 @@ typedef struct __nfs41_session {
     nfs41_cb_session cb_session;
 } nfs41_session;
 
+/* nfs41_root reference counting:
+ * similar to nfs41_open_state, the driver holds an implicit reference
+ * between MOUNT and UNMOUNT. all other upcalls use upcall_root_ref() on
+ * upcall_parse(), which prevents the root/clients from being freed and
+ * guarantees a matching deref on upcall_cleanup() */
 typedef struct __nfs41_root {
     client_owner4 client_owner;
     CRITICAL_SECTION lock;
     struct list_entry clients;
     uint32_t wsize;
     uint32_t rsize;
+    LONG ref_count;
 } nfs41_root;
 
 
@@ -184,7 +190,10 @@ int nfs41_root_create(
     IN uint32_t rsize,
     OUT nfs41_root **root_out);
 
-void nfs41_root_free(
+void nfs41_root_ref(
+    IN nfs41_root *root);
+
+void nfs41_root_deref(
     IN nfs41_root *root);
 
 int nfs41_root_mount_addrs(

daemon/open.c

@@ -121,6 +121,7 @@ static int parse_open(unsigned char *buffer, uint32_t length, nfs41_upcall *upca
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->open_owner_id, sizeof(ULONG));
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->mode, sizeof(DWORD));
@@ -497,6 +498,7 @@ static int parse_close(unsigned char *buffer, uint32_t length, nfs41_upcall *upc
 
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(nfs41_open_state *));
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->remove, sizeof(BOOLEAN));

daemon/readdir.c

@@ -62,6 +62,7 @@ static int parse_readdir(unsigned char *buffer, uint32_t length, nfs41_upcall *u
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->root, sizeof(args->root));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(args->state));
     if (status) goto out;
     upcall_open_state_ref(upcall, args->state);

daemon/readwrite.c

@@ -47,6 +47,7 @@ static int parse_rw(unsigned char *buffer, uint32_t length, nfs41_upcall *upcall
     if (status) goto out;
     status = safe_read(&buffer, &length, &args->root, sizeof(args->root));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(args->state));
     if (status) goto out;
     upcall_open_state_ref(upcall, args->state);

daemon/setattr.c

@@ -500,6 +500,7 @@ static int parse_setexattr(unsigned char *buffer, uint32_t length, nfs41_upcall
 
     status = safe_read(&buffer, &length, &args->root, sizeof(args->root));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(args->state));
     if (status) goto out;
     upcall_open_state_ref(upcall, args->state);

daemon/symlink.c

@@ -197,6 +197,7 @@ static int parse_symlink(unsigned char *buffer, uint32_t length, nfs41_upcall *u
 
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->state, sizeof(nfs41_open_state *));
     if (status) goto out;
     upcall_open_state_ref(upcall, args->state);

daemon/upcall.c

@@ -186,4 +186,8 @@ void upcall_cleanup(
         nfs41_open_state_deref(upcall->state_ref);
         upcall->state_ref = NULL;
     }
+    if (upcall->root_ref) {
+        nfs41_root_deref(upcall->root_ref);
+        upcall->root_ref = NULL;
+    }
 }

daemon/upcall.h

@@ -180,6 +180,7 @@ typedef struct __nfs41_upcall {
     /* store referenced pointers with the upcall for
      * automatic dereferencing on upcall_cleanup();
      * see upcall_root_ref() and upcall_open_state_ref() */
+    nfs41_root              *root_ref;
     nfs41_open_state        *state_ref;
 } nfs41_upcall;
 
@@ -222,6 +223,14 @@ void upcall_cleanup(
     IN nfs41_upcall *upcall);
 
 
+static __inline void upcall_root_ref(
+    IN nfs41_upcall *upcall,
+    IN nfs41_root *root)
+{
+    nfs41_root_ref(root);
+    upcall->root_ref = root;
+}
+
 static __inline void upcall_open_state_ref(
     IN nfs41_upcall *upcall,
     IN nfs41_open_state *state)

daemon/volume.c

@@ -48,6 +48,7 @@ static int parse_volume(unsigned char *buffer, uint32_t length, nfs41_upcall *up
     volume_upcall_args *args = &upcall->args.volume;
     status = safe_read(&buffer, &length, &args->root, sizeof(HANDLE));
     if (status) goto out;
+    upcall_root_ref(upcall, args->root);
     status = safe_read(&buffer, &length, &args->query, sizeof(FS_INFORMATION_CLASS));
     if (status) goto out;