[PATCH] flush_cache_page while pte valid

Hugh Dickins
2002-11-11T18:17:41Z

On some architectures (cachetlb.txt gives HyperSparc as an example)
it is essential to flush_cache_page while pte is still valid: the
rmap VM diverged from the base 2.4 VM before that fix was made,
so this error has crept back into 2.5.

Patch below applies to 2.5.47 or 2.5.47-mm1 - needs more work over
shared pagetables, but they've silently fallen out of 2.5.47-mm1:
oversight? I'll send Alan the equivalent for 2.4-ac shortly.

(I wonder, what happens if userspace now modifies the page
after the flush_cache_page, before the pte is invalidated?)

--- 2.5.47/mm/rmap.c Mon Oct 7 20:37:50 2002
+++ linux/mm/rmap.c Mon Nov 11 17:01:27 2002
@@ -393,9 +393,9 @@
}

/* Nuke the page table entry. */
+ flush_cache_page(vma, address);
pte = ptep_get_and_clear(ptep);
flush_tlb_page(vma, address);
- flush_cache_page(vma, address);

/* Store the swap location in the pte. See handle_pte_fault() ... */
if (PageSwapCache(page)) {