From b0506e488da5cf2f07f3a4f6d7acaa8f459ad714 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Wed, 22 Feb 2017 15:43:28 -0800
Subject: [PATCH] userfaultfd: shmem: introduce vma_is_shmem
Currently userfault relies on vma_is_anonymous and vma_is_hugetlb to
ensure compatibility of a VMA with userfault. Introduction of
vma_is_shmem allows detection if tmpfs backed VMAs, so that they may be
used with userfaultfd. Current implementation presumes usage of
vma_is_shmem only by slow path routines in userfaultfd, therefore the
vma_is_shmem is not made inline to leave the few remaining free bits in
vm_flags.
Link: http://lkml.kernel.org/r/20161216144821.5183-30-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/mm.h | 10 ++++++++++
mm/shmem.c | 5 +++++
2 files changed, 15 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c3e2be2b32960..bb997493e15d2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1383,6 +1383,16 @@ static inline bool vma_is_anonymous(struct vm_area_struct *vma)
return !vma->vm_ops;
}
+#ifdef CONFIG_SHMEM
+/*
+ * The vma_is_shmem is not inline because it is used only by slow
+ * paths in userfault.
+ */
+bool vma_is_shmem(struct vm_area_struct *vma);
+#else
+static inline bool vma_is_shmem(struct vm_area_struct *vma) { return false; }
+#endif
+
static inline int stack_guard_page_start(struct vm_area_struct *vma,
unsigned long addr)
{
diff --git a/mm/shmem.c b/mm/shmem.c
index 14de2a9e5083e..8412baec17cda 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -191,6 +191,11 @@ static const struct inode_operations shmem_special_inode_operations;
static const struct vm_operations_struct shmem_vm_ops;
static struct file_system_type shmem_fs_type;
+bool vma_is_shmem(struct vm_area_struct *vma)
+{
+ return vma->vm_ops == &shmem_vm_ops;
+}
+
static LIST_HEAD(shmem_swaplist);
static DEFINE_MUTEX(shmem_swaplist_mutex);
--
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