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From: Felix Fietkau <nbd@nbd.name>
Date: Sun, 24 Jan 2016 01:03:51 +0100
Subject: [PATCH] MIPS: fix cache flushing for highmem pages
Most cache flush ops were no-op for highmem pages. This led to nasty
segfaults and (in the case of page_address(page) == NULL) kernel
crashes.
Fix this by always flushing highmem pages using kmap/kunmap_atomic
around the actual cache flush. This might be a bit inefficient, but at
least it's stable.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -115,6 +115,13 @@ void __flush_anon_page(struct page *page
{
unsigned long addr = (unsigned long) page_address(page);
+ if (PageHighMem(page)) {
+ addr = (unsigned long)kmap_atomic(page);
+ flush_data_cache_page(addr);
+ __kunmap_atomic((void *)addr);
+ return;
+ }
+
if (pages_do_alias(addr, vmaddr)) {
if (page_mapcount(page) && !Page_dcache_dirty(page)) {
void *kaddr;
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