Suggest non-gki kernel users to backport path_umount

kernel/Makefile

@@ -62,6 +62,13 @@ $(info -- KernelSU Manager signature hash: $(KSU_EXPECTED_HASH))
 ccflags-y += -DEXPECTED_SIZE=$(KSU_EXPECTED_SIZE)
 ccflags-y += -DEXPECTED_HASH=\"$(KSU_EXPECTED_HASH)\"
 
+ifeq ($(shell grep -q "int path_umount" $(srctree)/fs/namespace.c; echo $$?),0)
+ccflags-y += -DKSU_UMOUNT
+else
+$(info -- Did you know you can backport path_umount to fs/namespace.c from 5.9?)
+$(info -- Read: https://kernelsu.org/guide/how-to-integrate-for-non-gki.html#path_umount)
+endif
+
 ccflags-y += -Wno-implicit-function-declaration -Wno-strict-prototypes -Wno-int-conversion -Wno-gcc-compat
 ccflags-y += -Wno-declaration-after-statement -Wno-unused-function
 

kernel/core_hook.c

@@ -513,7 +513,7 @@ static bool should_umount(struct path *path)
 
 static void ksu_umount_mnt(struct path *path, int flags)
 {
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 9, 0)
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 9, 0) || KSU_UMOUNT
 	int err = path_umount(path, flags);
 	if (err) {
 		pr_info("umount %s failed: %d\n", path->dentry->d_iname, err);

website/docs/guide/how-to-integrate-for-non-gki.md

@@ -40,6 +40,11 @@ But if you encounter a boot loop when integrated KernelSU, it is maybe *kprobe i
 comment out `ksu_enable_sucompat()` and `ksu_enable_ksud()` in `KernelSU/kernel/ksu.c`, if the device boots normally, then kprobe may be broken.
 :::
 
+:::info How to get module umount feature working on pre-GKI?
+
+If your kernel is older than 5.9, you should backport ```path_umount``` to ```fs/namespace.c```. This is required to get module umount feature working. If you don't backport ```path_umount```, module umount feature won't work. You can get more info on how to achieve this at the end of this page. 
+:::
+
 ## Manually modify the kernel source
 
 If kprobe does not work in your kernel (may be an upstream or kernel bug below 4.8), then you can try this way:
@@ -292,6 +297,55 @@ index 45306f9ef247..815091ebfca4 100755
  		add_input_randomness(type, code, value);
 ```
 
+## path_umount
+
+You can get module umount feature working on pre-GKI kernels by manually backporting ```path_umount``` from 5.9. You can use this patch as reference:
+
+```diff
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1739,6 +1739,39 @@ static inline bool may_mandlock(void)
+ }
+ #endif
+
++static int can_umount(const struct path *path, int flags)
++{
++	struct mount *mnt = real_mount(path->mnt);
++
++	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
++		return -EINVAL;
++	if (!may_mount())
++		return -EPERM;
++	if (path->dentry != path->mnt->mnt_root)
++		return -EINVAL;
++	if (!check_mnt(mnt))
++		return -EINVAL;
++	if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
++		return -EINVAL;
++	if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
++		return -EPERM;
++	return 0;
++}
++
++int path_umount(struct path *path, int flags)
++{
++	struct mount *mnt = real_mount(path->mnt);
++	int ret;
++
++	ret = can_umount(path, flags);
++	if (!ret)
++		ret = do_umount(mnt, flags);
++
++	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
++	dput(path->dentry);
++	mntput_no_expire(mnt);
++	return ret;
++}
+ /*
+  * Now umount can handle mount points as well as block devices.
+  * This is important for filesystems which use unnamed block devices.
+```
+
 Finally, build your kernel again, KernelSU should work well.
 
 :::info Entering safe mode accidiently?