From 3bf07641ee5ba1c6ec56b81a7f34abe1267d3ac1 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Wed, 4 May 2022 13:49:38 +0200
Subject: kernel: refcount vfs_backend

what a mess
---
 src/kernel/vfs/mount.c   |  3 +++
 src/kernel/vfs/request.c | 17 +++++++++++++++++
 src/kernel/vfs/request.h | 10 ++++++++++
 3 files changed, 30 insertions(+)

(limited to 'src/kernel/vfs')

diff --git a/src/kernel/vfs/mount.c b/src/kernel/vfs/mount.c
index 3fe192d..d13c3d6 100644
--- a/src/kernel/vfs/mount.c
+++ b/src/kernel/vfs/mount.c
@@ -8,6 +8,7 @@ struct vfs_mount *vfs_mount_seed(void) {
 	struct vfs_backend *backend = kmalloc(sizeof *backend);
 	backend->type = VFS_BACK_ROOT;
 	backend->potential_handlers = 1;
+	backend->refcount = 1;
 	*mount = (struct vfs_mount){
 		.prev = NULL,
 		.prefix = NULL,
@@ -45,6 +46,8 @@ void vfs_mount_remref(struct vfs_mount *mnt) {
 	if (--(mnt->refs) > 0) return;
 
 	struct vfs_mount *prev = mnt->prev;
+	if (mnt->backend)
+		vfs_backend_refdown(mnt->backend);
 	kfree(mnt->prefix);
 	kfree(mnt);
 
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 1f3193f..edb1fce 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -11,6 +11,9 @@ int vfs_request_create(struct vfs_request req_) {
 	memcpy(req, &req_, sizeof *req);
 	/* freed in vfs_request_finish or vfs_request_cancel */
 
+	if (req->backend)
+		req->backend->refcount++;
+
 	if (req->caller) {
 		process_transition(req->caller, PS_WAITS4FS);
 		req->caller->waits4fs.req = req;
@@ -87,6 +90,7 @@ int vfs_request_finish(struct vfs_request *req, int ret) {
 
 		struct handle *backing = handle_init(HANDLE_FILE);
 		backing->file.backend = req->backend;
+		req->backend->refcount++;
 		backing->file.id = ret;
 		req->caller->handles[handle] = backing;
 		ret = handle;
@@ -101,11 +105,13 @@ int vfs_request_finish(struct vfs_request *req, int ret) {
 		process_transition(req->caller, PS_RUNNING);
 	}
 
+	vfs_backend_refdown(req->backend);
 	kfree(req);
 	return ret;
 }
 
 void vfs_request_cancel(struct vfs_request *req, int ret) {
+	// TODO merge with vfs_request_finish
 	if (req->caller) {
 		assert(req->caller->state == PS_WAITS4FS);
 
@@ -118,5 +124,16 @@ void vfs_request_cancel(struct vfs_request *req, int ret) {
 		regs_savereturn(&req->caller->regs, ret);
 		process_transition(req->caller, PS_RUNNING);
 	}
+
+	vfs_backend_refdown(req->backend);
 	kfree(req);
 }
+
+void vfs_backend_refdown(struct vfs_backend *b) {
+	assert(b);
+	assert(b->refcount > 0);
+	if (--(b->refcount) > 0) return;
+
+	assert(!b->queue);
+	kfree(b);
+}
diff --git a/src/kernel/vfs/request.h b/src/kernel/vfs/request.h
index 657ae85..69dad07 100644
--- a/src/kernel/vfs/request.h
+++ b/src/kernel/vfs/request.h
@@ -11,6 +11,14 @@ enum vfs_backend_type {
 
 // describes something which can act as an access function
 struct vfs_backend {
+	size_t refcount;
+	/* references:
+	 *   struct vfs_mount
+	 *   struct vfs_request
+	 *   struct process
+	 *   struct handle
+	 */
+
 	enum vfs_backend_type type;
 
 	size_t potential_handlers; // 0 - orphaned
@@ -52,3 +60,5 @@ int vfs_backend_accept(struct vfs_backend *);
 int vfs_request_finish(struct vfs_request *, int ret);
 
 void vfs_request_cancel(struct vfs_request *, int ret);
+
+void vfs_backend_refdown(struct vfs_backend *);
-- 
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