From 8bc9542f9dadb9a99f92c20af3291a048e3a75fd Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 21 Aug 2024 11:58:32 -0400
Subject: kernel: vfs: Add sys_close()

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/kern/vfs_syscalls.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'sys/kern/vfs_syscalls.c')

diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 937ae87..77070ab 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -34,6 +34,7 @@
 #include <sys/errno.h>
 #include <sys/sio.h>
 #include <sys/filedesc.h>
+#include <sys/atomic.h>
 #include <sys/namei.h>
 #include <sys/proc.h>
 #include <sys/limits.h>
@@ -139,6 +140,40 @@ sys_open(struct syscall_args *scargs)
     return filedes->fdno;
 }
 
+/*
+ * arg0: fd
+ */
+scret_t
+sys_close(struct syscall_args *args)
+{
+    struct filedesc *filedes;
+    struct proc *td;
+    int fd = args->arg0;
+
+    if ((filedes = fd_get(fd)) == NULL) {
+        return -EBADF;
+    }
+
+    /* Return if other threads still hold a ref */
+    if (atomic_dec_int(&filedes->refcnt) > 0) {
+        return 0;
+    }
+
+    td = this_td();
+
+    /*
+     * Each file descriptor structure references a vnode,
+     * we want to reclaim it or at the very least drop
+     * one of its references. After we've cleaned up within
+     * the file descriptor, we can clear it from the fd table
+     * and free up the memory for it.
+     */
+    vfs_release_vnode(filedes->vp);
+    td->fds[fd] = NULL;
+    dynfree(filedes);
+    return 0;
+}
+
 /*
  * arg0: fd
  * arg1: buf
-- 
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