lib: fs: implement memory-mapped file i/o

lib/libfs/context.c

@@ -1,6 +1,7 @@
 #include "btree.h"
 #include "file.h"
 #include "interface.h"
+#include "mapping.h"
 
 #include <fs/allocator.h>
 #include <fs/context.h>
@@ -8,9 +9,16 @@
 #include <fs/inode.h>
 #include <fs/status.h>
 #include <fs/superblock.h>
+#include <mango/handle.h>
 #include <mango/log.h>
+#include <mango/object.h>
+#include <mango/signal.h>
+#include <mango/task.h>
+#include <mango/vm.h>
 #include <stdio.h>
 
+#define TEMP_OBJECT_SIZE 0x10000
+
 BTREE_DEFINE_SIMPLE_GET(struct fs_file, unsigned long, f_node, f_id, get_file);
 BTREE_DEFINE_SIMPLE_INSERT(struct fs_file, f_node, f_id, put_file);
 
@@ -18,12 +26,21 @@ struct fs_context {
 	struct fs_superblock *ctx_sb;
 	struct fs_allocator *ctx_alloc;
 	struct btree ctx_filelist;
+	kern_handle_t ctx_vm_controller;
+	kern_handle_t ctx_channel;
+	kern_handle_t ctx_temp_object;
+	void *ctx_temp_object_buf;
 
 	struct fs_vtable ctx_vtable;
 };
 
 struct fs_context *fs_context_create(struct fs_allocator *alloc)
 {
+	kern_handle_t self, address_space;
+	task_self(&self);
+	task_get_address_space(self, &address_space);
+	kern_handle_close(self);
+
 	struct fs_context *ctx = fs_alloc(alloc, sizeof *ctx);
 	if (!ctx) {
 		return NULL;
@@ -31,10 +48,48 @@ struct fs_context *fs_context_create(struct fs_allocator *alloc)
 
 	memset(ctx, 0x0, sizeof *ctx);
 
+	kern_status_t status = vm_controller_create(&ctx->ctx_vm_controller);
+	if (status != KERN_OK) {
+		fs_free(alloc, ctx);
+		return NULL;
+	}
+
+	status = vm_object_create(
+		NULL,
+		0,
+		TEMP_OBJECT_SIZE,
+		VM_PROT_READ | VM_PROT_WRITE | VM_PROT_USER,
+		&ctx->ctx_temp_object);
+	if (status != KERN_OK) {
+		kern_handle_close(ctx->ctx_vm_controller);
+		fs_free(alloc, ctx);
+		return NULL;
+	}
+
+	virt_addr_t temp_buffer;
+	status = address_space_map(
+		address_space,
+		MAP_ADDRESS_ANY,
+		ctx->ctx_temp_object,
+		0,
+		TEMP_OBJECT_SIZE,
+		VM_PROT_READ | VM_PROT_WRITE | VM_PROT_USER,
+		&temp_buffer);
+	if (status != KERN_OK) {
+		kern_handle_close(ctx->ctx_temp_object);
+		kern_handle_close(ctx->ctx_vm_controller);
+		fs_free(alloc, ctx);
+		return NULL;
+	}
+
+	ctx->ctx_temp_object_buf = (void *)temp_buffer;
 	ctx->ctx_alloc = alloc;
 
 	ctx->ctx_vtable.open = fs_msg_open;
+	ctx->ctx_vtable.close = fs_msg_close;
 	ctx->ctx_vtable.read = fs_msg_read;
+	ctx->ctx_vtable.write = fs_msg_write;
+	ctx->ctx_vtable.map = fs_msg_map;
 
 	return ctx;
 }
@@ -73,6 +128,112 @@ enum fs_status fs_context_unmount_filesystem(struct fs_context *ctx)
 	return FS_ERR_NOT_IMPLEMENTED;
 }
 
+void fs_context_set_channel(struct fs_context *ctx, kern_handle_t channel)
+{
+	ctx->ctx_channel = channel;
+}
+
+kern_handle_t fs_context_get_vm_controller(const struct fs_context *ctx)
+{
+	return ctx->ctx_vm_controller;
+}
+
+static enum fs_status handle_msg(struct fs_context *ctx)
+{
+	xpc_msg_t msg;
+	kern_status_t status = xpc_msg_recv_nowait(ctx->ctx_channel, &msg);
+	if (status == KERN_NO_ENTRY) {
+		return FS_SUCCESS;
+	}
+
+	if (status != KERN_OK) {
+		kern_logf("message recv error %d", status);
+		return FS_ERR_INTERNAL_FAILURE;
+	}
+
+	switch (msg.msg_header.hdr_interface) {
+	case INTERFACE_FS:
+		status = fs_context_dispatch_msg(ctx, &msg);
+		break;
+	default:
+		kern_logf(
+			"unknown message protocol %u",
+			msg.msg_header.hdr_interface);
+		xpc_msg_reply_error(&msg, KERN_UNSUPPORTED);
+		break;
+	}
+
+	return FS_SUCCESS;
+}
+
+static enum fs_status handle_page_request(struct fs_context *ctx)
+{
+	equeue_packet_page_request_t packet;
+	vm_controller_recv(ctx->ctx_vm_controller, &packet);
+	struct file_mapping *mapping = (struct file_mapping *)packet.req_vmo;
+	kern_logf(
+		"received page request [%zx-%zx] for file %s",
+		packet.req_offset,
+		packet.req_offset + packet.req_length,
+		mapping->m_file->f_dent->d_name);
+
+	size_t length = packet.req_length;
+	if (length > TEMP_OBJECT_SIZE) {
+		length = TEMP_OBJECT_SIZE;
+	}
+
+	char *dst = ctx->ctx_temp_object_buf;
+	xpc_buffer_t buf = XPC_LOCAL_BUFFER_OUT(dst, TEMP_OBJECT_SIZE);
+	enum fs_status status = fs_file_read_at(
+		mapping->m_file,
+		&buf,
+		mapping->m_file_offset + packet.req_offset,
+		length);
+	if (status != FS_SUCCESS) {
+		kern_logf("map-read failed with code %d", status);
+		return status;
+	}
+
+	vm_controller_supply_pages(
+		ctx->ctx_vm_controller,
+		mapping->m_vmo,
+		packet.req_offset,
+		ctx->ctx_temp_object,
+		0,
+		packet.req_length);
+	return FS_SUCCESS;
+}
+
+enum fs_status fs_context_handle_request(struct fs_context *ctx)
+{
+	kern_wait_item_t waiters[] = {
+		{
+			.w_handle = ctx->ctx_channel,
+			.w_waitfor = CHANNEL_SIGNAL_MSG_RECEIVED,
+		},
+		{
+			.w_handle = ctx->ctx_vm_controller,
+			.w_waitfor = VM_CONTROLLER_SIGNAL_REQUEST_RECEIVED,
+		},
+	};
+	const size_t nr_waiters = sizeof waiters / sizeof waiters[0];
+
+	kern_status_t kstatus = kern_object_wait(waiters, nr_waiters);
+	if (kstatus != KERN_OK) {
+		return FS_ERR_INTERNAL_FAILURE;
+	}
+
+	if (waiters[0].w_observed & CHANNEL_SIGNAL_MSG_RECEIVED) {
+		return handle_msg(ctx);
+	}
+
+	if (waiters[1].w_observed & VM_CONTROLLER_SIGNAL_REQUEST_RECEIVED) {
+		return handle_page_request(ctx);
+	}
+
+	return FS_SUCCESS;
+}
+
 struct fs_file *fs_context_open_file(struct fs_context *ctx, unsigned long id)
 {
 	struct fs_file *f = get_file(&ctx->ctx_filelist, id);