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Subject[PATCH v2 19/26] userfaultfd: introduce helper vma_find_uffd
Date
We've have multiple (and more coming) places that would like to find a
userfault enabled VMA from a mm struct that covers a specific memory
range. This patch introduce the helper for it, meanwhile apply it to
the code.

Suggested-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/userfaultfd.c | 54 +++++++++++++++++++++++++++---------------------
1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 80bcd642911d..fefa81c301b7 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -20,6 +20,34 @@
#include <asm/tlbflush.h>
#include "internal.h"

+/*
+ * Find a valid userfault enabled VMA region that covers the whole
+ * address range, or NULL on failure. Must be called with mmap_sem
+ * held.
+ */
+static struct vm_area_struct *vma_find_uffd(struct mm_struct *mm,
+ unsigned long start,
+ unsigned long len)
+{
+ struct vm_area_struct *vma = find_vma(mm, start);
+
+ if (!vma)
+ return NULL;
+
+ /*
+ * Check the vma is registered in uffd, this is required to
+ * enforce the VM_MAYWRITE check done at uffd registration
+ * time.
+ */
+ if (!vma->vm_userfaultfd_ctx.ctx)
+ return NULL;
+
+ if (start < vma->vm_start || start + len > vma->vm_end)
+ return NULL;
+
+ return vma;
+}
+
static int mcopy_atomic_pte(struct mm_struct *dst_mm,
pmd_t *dst_pmd,
struct vm_area_struct *dst_vma,
@@ -228,20 +256,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
*/
if (!dst_vma) {
err = -ENOENT;
- dst_vma = find_vma(dst_mm, dst_start);
+ dst_vma = vma_find_uffd(dst_mm, dst_start, len);
if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
goto out_unlock;
- /*
- * Check the vma is registered in uffd, this is
- * required to enforce the VM_MAYWRITE check done at
- * uffd registration time.
- */
- if (!dst_vma->vm_userfaultfd_ctx.ctx)
- goto out_unlock;
-
- if (dst_start < dst_vma->vm_start ||
- dst_start + len > dst_vma->vm_end)
- goto out_unlock;

err = -EINVAL;
if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
@@ -488,20 +505,9 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
* both valid and fully within a single existing vma.
*/
err = -ENOENT;
- dst_vma = find_vma(dst_mm, dst_start);
+ dst_vma = vma_find_uffd(dst_mm, dst_start, len);
if (!dst_vma)
goto out_unlock;
- /*
- * Check the vma is registered in uffd, this is required to
- * enforce the VM_MAYWRITE check done at uffd registration
- * time.
- */
- if (!dst_vma->vm_userfaultfd_ctx.ctx)
- goto out_unlock;
-
- if (dst_start < dst_vma->vm_start ||
- dst_start + len > dst_vma->vm_end)
- goto out_unlock;

err = -EINVAL;
/*
--
2.17.1
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