msync over reserved mem

[Andrea Arcangeli]

This patch fixes the troubles generated by msync on /dev/fb0 or any
other device driver that exports reserved memory to userspace via shared
mapping.

--- 2.4.5pre1aa3/mm/filemap.c.~1~	Fri May 11 02:08:28 2001
+++ 2.4.5pre1aa3/mm/filemap.c	Mon May 14 18:48:59 2001
@@ -1808,10 +1808,12 @@
 {
 	pte_t pte = *ptep;
 
-	if (pte_present(pte) && ptep_test_and_clear_dirty(ptep)) {
+	if (pte_present(pte)) {
 		struct page *page = pte_page(pte);
-		flush_tlb_page(vma, address);
-		set_page_dirty(page);
+		if (VALID_PAGE(page) && !PageReserved(page) && ptep_test_and_clear_dirty(ptep)) {
+			flush_tlb_page(vma, address);
+			set_page_dirty(page);
+		}
 	}
 	return 0;
 }

Andrea