Introduces two new helper functions:
* munmap_addr_sanity()
* munmap_lookup_vma()
They will be used by do_munmap() and the new do_munmap with zapping
large mapping early in the later patch.
There is no functional change, just code refactor.
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
mm/mmap.c | 107 ++++++++++++++++++++++++++++++++++++++++++--------------------
1 file changed, 72 insertions(+), 35 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index d1eb87e..87dcf83 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2686,34 +2686,45 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
return __split_vma(mm, vma, addr, new_below);
}
-/* Munmap is split into 2 main parts -- this part which finds
- * what needs doing, and the areas themselves, which do the
- * work. This now handles partial unmappings.
- * Jeremy Fitzhardinge <jeremy@xxxxxxxx>
- */
-int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
- struct list_head *uf)
+static inline bool munmap_addr_sanity(unsigned long start, size_t len)
{
- unsigned long end;
- struct vm_area_struct *vma, *prev, *last;
+ if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE - start)
+ return false;
- if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
- return -EINVAL;
+ if (PAGE_ALIGN(len) == 0)
+ return false;
- len = PAGE_ALIGN(len);
- if (len == 0)
- return -EINVAL;
+ return true;
+}
+
+/*
+ * munmap_lookup_vma: find the first overlap vma and split overlap vmas.
+ * @mm: mm_struct
+ * @vma: the first overlapping vma
+ * @prev: vma's prev
+ * @start: start address
+ * @end: end address
+ *
+ * returns 1 if successful, 0 or errno otherwise
+ */
+static int munmap_lookup_vma(struct mm_struct *mm, struct vm_area_struct **vma,
+ struct vm_area_struct **prev, unsigned long start,
+ unsigned long end)
+{
+ struct vm_area_struct *tmp, *last;
+ int ret;
/* Find the first overlapping VMA */
- vma = find_vma(mm, start);
- if (!vma)
+ tmp = find_vma(mm, start);
+ if (!tmp)
return 0;
- prev = vma->vm_prev;
- /* we have start < vma->vm_end */
+
+ *prev = tmp->vm_prev;
+
+ /* we have start < vma->vm_end */
/* if it doesn't overlap, we have nothing.. */
- end = start + len;
- if (vma->vm_start >= end)
+ if (tmp->vm_start >= end)
return 0;
/*
@@ -2723,31 +2734,57 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
* unmapped vm_area_struct will remain in use: so lower split_vma
* places tmp vma above, and higher split_vma places tmp vma below.
*/
- if (start > vma->vm_start) {
- int error;
-
+ if (start > tmp->vm_start) {
/*
* Make sure that map_count on return from munmap() will
* not exceed its limit; but let map_count go just above
* its limit temporarily, to help free resources as expected.
*/
- if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
+ if (end < tmp->vm_end &&
+ mm->map_count > sysctl_max_map_count)
return -ENOMEM;
- error = __split_vma(mm, vma, start, 0);
- if (error)
- return error;
- prev = vma;
+ ret = __split_vma(mm, tmp, start, 0);
+ if (ret)
+ return ret;
+ *prev = tmp;
}
/* Does it split the last one? */
last = find_vma(mm, end);
if (last && end > last->vm_start) {
- int error = __split_vma(mm, last, end, 1);
- if (error)
- return error;
+ ret = __split_vma(mm, last, end, 1);
+ if (ret)
+ return ret;
}
- vma = prev ? prev->vm_next : mm->mmap;
+
+ *vma = *prev ? (*prev)->vm_next : mm->mmap;
+
+ return 1;
+}
+
+/* Munmap is split into 2 main parts -- this part which finds
+ * what needs doing, and the areas themselves, which do the
+ * work. This now handles partial unmappings.
+ * Jeremy Fitzhardinge <jeremy@xxxxxxxx>
+ */
+int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
+ struct list_head *uf)
+{
+ unsigned long end;
+ struct vm_area_struct *vma = NULL, *prev;
+ int ret = 0;
+
+ if (!munmap_addr_sanity(start, len))
+ return -EINVAL;
+
+ len = PAGE_ALIGN(len);
+
+ end = start + len;
+
+ ret = munmap_lookup_vma(mm, &vma, &prev, start, end);
+ if (ret != 1)
+ return ret;
if (unlikely(uf)) {
/*
@@ -2759,9 +2796,9 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
* split, despite we could. This is unlikely enough
* failure that it's not worth optimizing it for.
*/
- int error = userfaultfd_unmap_prep(vma, start, end, uf);
- if (error)
- return error;
+ ret = userfaultfd_unmap_prep(vma, start, end, uf);
+ if (ret)
+ return ret;
}
/*
--
1.8.3.1
