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-rw-r--r--mm/mmap.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 02c09f3..d9c77b2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1198,8 +1198,20 @@ munmap_back:
goto free_vma;
}
- if (vma_wants_writenotify(vma))
+ if (vma_wants_writenotify(vma)) {
+ pgprot_t pprot = vma->vm_page_prot;
+
+ /* Can vma->vm_page_prot have changed??
+ *
+ * Answer: Yes, drivers may have changed it in their
+ * f_op->mmap method.
+ *
+ * Ensures that vmas marked as uncached stay that way.
+ */
vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
+ if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+ }
vma_link(mm, vma, prev, rb_link, rb_parent);
file = vma->vm_file;
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