From 42e4b941b70499f5cf10f41126af1634821d72d5 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Fri, 15 Apr 2022 23:42:43 +0200
Subject: kernel/vfs: don't hang on orphaned vfs calls

---
 src/kernel/proc.c        | 19 +++++++++++++++++--
 src/kernel/syscalls.c    |  1 +
 src/kernel/vfs/mount.c   |  1 +
 src/kernel/vfs/request.c | 16 ++++++++++++++--
 src/kernel/vfs/request.h |  4 ++++
 5 files changed, 37 insertions(+), 4 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index ad2a72b..9779478 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -54,6 +54,9 @@ struct process *process_fork(struct process *parent) {
 
 	parent->handled_req = NULL; // TODO control this with a flag
 
+	if (child->controlled)
+		child->controlled->potential_handlers++;
+
 	child->id      = next_pid++;
 
 	return child;
@@ -189,9 +192,21 @@ void process_transition(struct process *p, enum process_state state) {
 
 void process_kill(struct process *proc, int ret) {
 	// TODO kill children
+	if (proc->controlled) {
+		proc->controlled->potential_handlers--;
+		if (proc->controlled->potential_handlers == 0) {
+			// orphaned
+			struct process *q = proc->controlled->queue;
+			while (q) {
+				assert(q->state == PS_WAITS4FS);
+				struct process *q2 = q->waits4fs.queue_next;
+				vfs_request_cancel(&q->waits4fs.req, ret);
+				q = q2;
+			}
+		}
+	}
 	if (proc->handled_req) {
-		regs_savereturn(&proc->handled_req->caller->regs, -1);
-		process_transition(proc->handled_req->caller, PS_RUNNING);
+		vfs_request_cancel(proc->handled_req, ret);
 	}
 	process_transition(proc, PS_DEAD);
 	proc->death_msg = ret;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 217fa77..31bd0de 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -189,6 +189,7 @@ handle_t _syscall_fs_fork2(void) {
 
 	backend = kmalloc(sizeof *backend); // TODO never freed
 	backend->type = VFS_BACK_USER;
+	backend->potential_handlers = 1;
 	backend->handler = NULL;
 	backend->queue = NULL;
 
diff --git a/src/kernel/vfs/mount.c b/src/kernel/vfs/mount.c
index c962ba5..423bf10 100644
--- a/src/kernel/vfs/mount.c
+++ b/src/kernel/vfs/mount.c
@@ -6,6 +6,7 @@ struct vfs_mount *vfs_mount_seed(void) {
 	struct vfs_mount   *mount   = kmalloc(sizeof *mount);
 	struct vfs_backend *backend = kmalloc(sizeof *backend);
 	backend->type = VFS_BACK_ROOT;
+	backend->potential_handlers = 1;
 	*mount = (struct vfs_mount){
 		.prev = NULL,
 		.prefix = "",
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 687f456..277c353 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -14,7 +14,7 @@ int vfs_request_create(struct vfs_request req_) {
 	process_current->waits4fs.req = req_;
 	req = &process_current->waits4fs.req;
 
-	if (!req->backend)
+	if (!req->backend || !req->backend->potential_handlers)
 		return vfs_request_finish(req, -1);
 
 	switch (req->backend->type) {
@@ -89,10 +89,22 @@ int vfs_request_finish(struct vfs_request *req, int ret) {
 		ret = handle;
 	}
 
-	if (req->input.kern)  kfree(req->input.buf_kern);
+	if (req->input.kern)
+		kfree(req->input.buf_kern);
 
 	assert(req->caller->state == PS_WAITS4FS || req->caller->state == PS_WAITS4IRQ);
 	process_transition(req->caller, PS_RUNNING);
 	regs_savereturn(&req->caller->regs, ret);
 	return ret;
 }
+
+void vfs_request_cancel(struct vfs_request *req, int ret) {
+	if (req->input.kern)
+		kfree(req->input.buf_kern);
+
+	// ret must always be negative, so it won't be confused with a success
+	if (ret > 0) ret = -ret;
+	if (ret == 0) ret = -1;
+	regs_savereturn(&req->caller->regs, ret);
+	process_transition(req->caller, PS_RUNNING);
+}
diff --git a/src/kernel/vfs/request.h b/src/kernel/vfs/request.h
index ce5a7fb..1e3ef60 100644
--- a/src/kernel/vfs/request.h
+++ b/src/kernel/vfs/request.h
@@ -13,6 +13,8 @@ enum vfs_backend_type {
 struct vfs_backend {
 	enum vfs_backend_type type;
 
+	size_t potential_handlers; // 0 - orphaned
+
 	// only used with VFS_BACK_USER
 	struct process *handler;
 	struct process *queue;
@@ -45,3 +47,5 @@ struct vfs_request {
 int vfs_request_create(struct vfs_request);
 int vfs_request_accept(struct vfs_request *);
 int vfs_request_finish(struct vfs_request *, int ret);
+
+void vfs_request_cancel(struct vfs_request *, int ret);
-- 
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