userswap: introduce new flag to determine the first page fault

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

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

Introduce new flag to determine the first page fault.
Signed-off-by: NZhangPeng <zhangpeng362@huawei.com>

fs/userfaultfd.c

@@ -485,6 +485,10 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	uwq.wq.private = current;
 	uwq.msg = userfault_msg(vmf->address, vmf->flags, reason,
 			ctx->features);
+#ifdef CONFIG_USERSWAP
+	if (reason & VM_USWAP && pte_none(vmf->orig_pte))
+		uwq.msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_FPF;
+#endif
 	uwq.ctx = ctx;
 	uwq.waken = false;
 

include/linux/userswap.h

@@ -59,6 +59,13 @@ static inline bool uswap_vm_flag_bug_on(unsigned long reason)
 	return !(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP);
 }
 
+static inline bool uswap_missing(struct vm_area_struct *vma)
+{
+	if (vma->vm_flags & VM_USWAP && vma->vm_flags & VM_UFFD_MISSING)
+		return true;
+	return false;
+}
+
 #endif /* CONFIG_USERSWAP */
 
 #endif /* _LINUX_USERSWAP_H */

include/uapi/linux/userfaultfd.h

@@ -127,6 +127,7 @@ struct uffd_msg {
 /* flags for UFFD_EVENT_PAGEFAULT */
 #define UFFD_PAGEFAULT_FLAG_WRITE	(1<<0)	/* If this was a write fault */
 #define UFFD_PAGEFAULT_FLAG_WP		(1<<1)	/* If reason is VM_UFFD_WP */
+#define UFFD_PAGEFAULT_FLAG_FPF		(1<<10) /* If this was the first page fault */
 
 struct uffdio_api {
 	/* userland asks for an API number and the features to enable */

mm/memory.c

@@ -73,6 +73,7 @@
 #include <linux/perf_event.h>
 #include <linux/ptrace.h>
 #include <linux/vmalloc.h>
+#include <linux/userswap.h>
 
 #include <trace/events/kmem.h>
 
@@ -3689,6 +3690,12 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 		if (ret)
 			goto unlock;
 		/* Deliver the page fault to userland, check inside PT lock */
+#ifdef CONFIG_USERSWAP
+		if (uswap_missing(vma)) {
+			pte_unmap_unlock(vmf->pte, vmf->ptl);
+			return handle_userfault(vmf, VM_UFFD_MISSING|VM_USWAP);
+		}
+#endif
 		if (userfaultfd_missing(vma)) {
 			pte_unmap_unlock(vmf->pte, vmf->ptl);
 			return handle_userfault(vmf, VM_UFFD_MISSING);
@@ -3731,6 +3738,13 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 		goto release;
 
 	/* Deliver the page fault to userland, check inside PT lock */
+#ifdef CONFIG_USERSWAP
+	if (uswap_missing(vma)) {
+		pte_unmap_unlock(vmf->pte, vmf->ptl);
+		put_page(page);
+		return handle_userfault(vmf, VM_UFFD_MISSING | VM_USWAP);
+	}
+#endif
 	if (userfaultfd_missing(vma)) {
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 		put_page(page);