From 6a71c766e60a9ac12876a0ea8a10c997df2507a3 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Thu, 7 Apr 2022 22:21:31 +0200
Subject: kernel/vfs: implement a vfs request queue

---
 src/kernel/proc.h        |  5 ++++-
 src/kernel/syscalls.c    |  4 ++--
 src/kernel/vfs/request.c | 11 +++++++----
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 6723e23..5e328aa 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -27,7 +27,10 @@ struct process {
 	// saved value, meaning depends on .state
 	union {
 		int death_msg; // PS_DEAD
-		struct vfs_request pending_req; // PS_WAITS4FS
+		struct {
+			struct vfs_request req;
+			struct process *queue_next;
+		} waits4fs; // PS_WAITS4FS
 		struct {
 			char __user *buf;
 			int  max_len;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index faa7ccc..daf7cac 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -215,8 +215,8 @@ int _syscall_fs_wait(char __user *buf, int max_len, struct fs_wait_response __us
 	if (backend->queue) {
 		// handle queued requests
 		struct process *queued = backend->queue;
-		backend->queue = NULL; // TODO get the next queued proc
-		vfs_request_pass2handler(&queued->pending_req);
+		backend->queue = queued->waits4fs.queue_next;
+		vfs_request_pass2handler(&queued->waits4fs.req);
 	} else {
 		process_switch_any();
 	}
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 45a7ae7..0214ca7 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -10,10 +10,11 @@ int vfs_request_create(struct vfs_request req_) {
 	struct vfs_request *req;
 	int ret;
 	process_current->state = PS_WAITS4FS;
+	process_current->waits4fs.queue_next = NULL;
 
 	// the request is owned by the caller
-	process_current->pending_req = req_;
-	req = &process_current->pending_req;
+	process_current->waits4fs.req = req_;
+	req = &process_current->waits4fs.req;
 
 	if (!req->backend)
 		return vfs_request_finish(req, -1);
@@ -26,8 +27,10 @@ int vfs_request_create(struct vfs_request req_) {
 		case VFS_BACK_USER:
 			if (req->backend->handler == NULL) {
 				// backend isn't ready yet, join the queue
-				assert(req->backend->queue == NULL); // TODO implement a proper queue
-				req->backend->queue = process_current;
+				struct process **iter = &req->backend->queue;
+				while (*iter != NULL)
+					iter = &(*iter)->waits4fs.queue_next;
+				*iter = process_current;
 				process_switch_any();
 			} else {
 				vfs_request_pass2handler(req);
-- 
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