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Subject[PATCH] swapin flush cache bug

Hi,

Niibe Yutaka noted (and added an entry on the MM bugzilla system) that
cache flushing on do_swap_page() is buggy. Here:

---
struct page *page = lookup_swap_cache(entry);
pte_t pte;
if (!page) {
lock_kernel();
swapin_readahead(entry);
page = read_swap_cache(entry);
unlock_kernel();
if (!page)
return -1;
flush_page_to_ram(page);
flush_icache_page(vma, page);
}
mm->rss++;
--

If lookup_swap_cache() finds a page in the swap cache, and that page was
in memory because of the swapin readahead, the cache is not flushed.

Here is a patch to fix the problem by always flushing the cache including
for pages in the swap cache:

--- linux.orig/mm/memory.c.orig Thu Feb 8 10:52:20 2001
+++ linux/mm/memory.c Thu Feb 8 10:54:07 2001
@@ -1033,12 +1033,12 @@
unlock_kernel();
if (!page)
return -1;
-
- flush_page_to_ram(page);
- flush_icache_page(vma, page);
}

mm->rss++;
+
+ flush_page_to_ram(page);
+ flush_icache_page(vma, page);

pte = mk_pte(page, vma->vm_page_prot);



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