Re: [PATCH 2/6] mm: introduce vma_set_file function v3

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Am 09.10.20 um 17:14 schrieb Jason Gunthorpe:
On Fri, Oct 09, 2020 at 05:03:38PM +0200, Christian König wrote:
+/*
+ * Change backing file, only valid to use during initial VMA setup.
+ */
+void vma_set_file(struct vm_area_struct *vma, struct file *file)
+{
+	if (file)
+	        get_file(file);
+
+	swap(vma->vm_file, file);
+
+	if (file)
+		fput(file);
+}
fput crashes when file is NULL so the error handling after
unmap_and_free_vma: can't handle this case, similarly vm_file can't be
NULL either.

So just simply:

  swap(vma->vm_file, file);
  get_file(vma->vm_file);
  fput(file);
Will do?

I was considering this as well, yes.

Just let it crash if any of them are wrongly NULL.

Mhm, changing from anonymous to file backed or reverse is probably not such a good idea.

So yes catching those problems early is probably the best approach we could do.

Going to do this in v4 if nobody objects.

Regards,
Christian.


Jason






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