userswap: provide cpu info in userfault msg

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6CAIM

--------------------------------

The uffd_msg.reserved3 field is used to transfer the CPU information of
the PF.
Signed-off-by: NZhangPeng <zhangpeng362@huawei.com>

fs/userfaultfd.c

@@ -218,6 +218,9 @@ static inline struct uffd_msg userfault_msg(unsigned long address,
 		msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
 	if (features & UFFD_FEATURE_THREAD_ID)
 		msg.arg.pagefault.feat.ptid = task_pid_vnr(current);
+#ifdef CONFIG_USERSWAP
+	uswap_get_cpu_id(reason, &msg);
+#endif
 	return msg;
 }
 

include/linux/userswap.h

@@ -66,6 +66,12 @@ static inline bool uswap_missing(struct vm_area_struct *vma)
 	return false;
 }
 
+static inline void uswap_get_cpu_id(unsigned long reason, struct uffd_msg *msg)
+{
+	if (reason & VM_USWAP)
+		msg->reserved3 = smp_processor_id();
+}
+
 #endif /* CONFIG_USERSWAP */
 
 #endif /* _LINUX_USERSWAP_H */