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Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c57
1 files changed, 19 insertions, 38 deletions
diff --git a/mm/gup.c b/mm/gup.c
index a9d4d724aef7..7bc1ba9ce440 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1729,11 +1729,11 @@ EXPORT_SYMBOL(fault_in_writeable);
* @uaddr: start of address range
* @size: length of address range
*
- * Faults in an address range using get_user_pages, i.e., without triggering
- * hardware page faults. This is primarily useful when we already know that
- * some or all of the pages in the address range aren't in memory.
+ * Faults in an address range for writing. This is primarily useful when we
+ * already know that some or all of the pages in the address range aren't in
+ * memory.
*
- * Other than fault_in_writeable(), this function is non-destructive.
+ * Unlike fault_in_writeable(), this function is non-destructive.
*
* Note that we don't pin or otherwise hold the pages referenced that we fault
* in. There's no guarantee that they'll stay in memory for any duration of
@@ -1744,46 +1744,27 @@ EXPORT_SYMBOL(fault_in_writeable);
*/
size_t fault_in_safe_writeable(const char __user *uaddr, size_t size)
{
- unsigned long start = (unsigned long)untagged_addr(uaddr);
- unsigned long end, nstart, nend;
+ unsigned long start = (unsigned long)uaddr, end;
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma = NULL;
- int locked = 0;
+ bool unlocked = false;
- nstart = start & PAGE_MASK;
+ if (unlikely(size == 0))
+ return 0;
end = PAGE_ALIGN(start + size);
- if (end < nstart)
+ if (end < start)
end = 0;
- for (; nstart != end; nstart = nend) {
- unsigned long nr_pages;
- long ret;
- if (!locked) {
- locked = 1;
- mmap_read_lock(mm);
- vma = find_vma(mm, nstart);
- } else if (nstart >= vma->vm_end)
- vma = vma->vm_next;
- if (!vma || vma->vm_start >= end)
- break;
- nend = end ? min(end, vma->vm_end) : vma->vm_end;
- if (vma->vm_flags & (VM_IO | VM_PFNMAP))
- continue;
- if (nstart < vma->vm_start)
- nstart = vma->vm_start;
- nr_pages = (nend - nstart) / PAGE_SIZE;
- ret = __get_user_pages_locked(mm, nstart, nr_pages,
- NULL, NULL, &locked,
- FOLL_TOUCH | FOLL_WRITE);
- if (ret <= 0)
+ mmap_read_lock(mm);
+ do {
+ if (fixup_user_fault(mm, start, FAULT_FLAG_WRITE, &unlocked))
break;
- nend = nstart + ret * PAGE_SIZE;
- }
- if (locked)
- mmap_read_unlock(mm);
- if (nstart == end)
- return 0;
- return size - min_t(size_t, nstart - start, size);
+ start = (start + PAGE_SIZE) & PAGE_MASK;
+ } while (start != end);
+ mmap_read_unlock(mm);
+
+ if (size > (unsigned long)uaddr - start)
+ return size - ((unsigned long)uaddr - start);
+ return 0;
}
EXPORT_SYMBOL(fault_in_safe_writeable);