kernel: reference count mount objects, free them on process kills

2 files changed, 21 insertions, 1 deletions

diff --git a/src/kernel/vfs/mount.c b/src/kernel/vfs/mount.c
index 423bf10..3fe192d 100644
--- a/src/kernel/vfs/mount.c
+++ b/src/kernel/vfs/mount.c
@@ -1,4 +1,5 @@
 #include <kernel/mem/alloc.h>
+#include <kernel/panic.h>
 #include <kernel/vfs/mount.h>
 #include <shared/mem.h>
 
@@ -9,9 +10,10 @@ struct vfs_mount *vfs_mount_seed(void) {
 	backend->potential_handlers = 1;
 	*mount = (struct vfs_mount){
 		.prev = NULL,
-		.prefix = "",
+		.prefix = NULL,
 		.prefix_len = 0,
 		.backend = backend,
+		.refs = 1, // never to be freed
 	};
 	return mount;
 }
@@ -36,3 +38,15 @@ struct vfs_mount *vfs_mount_resolve(
 	}
 	return top;
 }
+
+void vfs_mount_remref(struct vfs_mount *mnt) {
+	assert(mnt);
+	assert(mnt->refs > 0);
+	if (--(mnt->refs) > 0) return;
+
+	struct vfs_mount *prev = mnt->prev;
+	kfree(mnt->prefix);
+	kfree(mnt);
+
+	if (prev) vfs_mount_remref(prev);
+}
diff --git a/src/kernel/vfs/mount.h b/src/kernel/vfs/mount.h
index 5fb6d16..96a2d7b 100644
--- a/src/kernel/vfs/mount.h
+++ b/src/kernel/vfs/mount.h
@@ -7,9 +7,15 @@ struct vfs_mount {
 	char *prefix;
 	size_t prefix_len;
 	struct vfs_backend *backend;
+	size_t refs; /* counts all references, atm from:
+	              *  - struct vfs_mount
+	              *  - struct proc
+	              */
 };
 
 // prepares init's filesystem view
 struct vfs_mount *vfs_mount_seed(void);
 struct vfs_mount *vfs_mount_resolve(
 		struct vfs_mount *top, const char *path, size_t path_len);
+/** Decrements the reference count, potentially freeing the mount. */
+void vfs_mount_remref(struct vfs_mount *mnt);