kernel: Add ref count to filedesc

Keep track of how many threads are currently using the file descriptor.
This will be useful when fork() is implemented.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 2 insertions, 0 deletions

diff --git a/sys/include/sys/filedesc.h b/sys/include/sys/filedesc.h
index 55f84e5..dbac349 100644
--- a/sys/include/sys/filedesc.h
+++ b/sys/include/sys/filedesc.h
@@ -38,6 +38,7 @@ struct filedesc {
     int fdno;
     off_t offset;
     bool is_dir;
+    int refcnt;
     struct vnode *vp;
     struct spinlock lock;
 };
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 371c1a5..937ae87 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -90,6 +90,7 @@ fd_alloc(struct filedesc **fd_out)
             return -ENOMEM;
         }
 
+        fd->refcnt = 1;
         fd->fdno = i;
         td->fds[i] = fd;