parisc: fix cache-flushing

This commit:
f8dae00684d678afa13041ef170cecfd1297ed40: parisc: Ensure full cache coherency for kmap/kunmap
caused negative caching side-effects, e.g. hanging processes with expect and
too many inequivalent alias messages from flush_dcache_page() on Debian 5 systems.

This patch now partly reverts it and has been in production use on our debian buildd
makeservers since a week without any major problems.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # v3.9+
Signed-off-by: Helge Deller <deller@gmx.de>

3 files changed, 16 insertions, 3 deletions

diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h
index 2f9b751878ba..de65f66ea64e 100644
--- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -132,7 +132,6 @@ void mark_rodata_ro(void);
 static inline void *kmap(struct page *page)
 {
         might_sleep();
-        flush_dcache_page(page);
         return page_address(page);
 }
 
@@ -144,7 +143,6 @@ static inline void kunmap(struct page *page)
 static inline void *kmap_atomic(struct page *page)
 {
         pagefault_disable();
-        flush_dcache_page(page);
         return page_address(page);
 }
 
diff --git a/arch/parisc/include/asm/page.h b/arch/parisc/include/asm/page.h
index c53fc63149e8..637fe031aa84 100644
--- a/arch/parisc/include/asm/page.h
+++ b/arch/parisc/include/asm/page.h
@@ -29,7 +29,8 @@ struct page;
 void clear_page_asm(void *page);
 void copy_page_asm(void *to, void *from);
 #define clear_user_page(vto, vaddr, page) clear_page_asm(vto)
-#define copy_user_page(vto, vfrom, vaddr, page) copy_page_asm(vto, vfrom)
+void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
+                        struct page *pg);
 
 /* #define CONFIG_PARISC_TMPALIAS */
 
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index a72545554a31..ac87a40502e6 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -388,6 +388,20 @@ void flush_kernel_dcache_page_addr(void *addr)
 }
 EXPORT_SYMBOL(flush_kernel_dcache_page_addr);
 
+void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
+        struct page *pg)
+{
+       /* Copy using kernel mapping.  No coherency is needed (all in
+          kunmap) for the `to' page.  However, the `from' page needs to
+          be flushed through a mapping equivalent to the user mapping
+          before it can be accessed through the kernel mapping. */
+        preempt_disable();
+        flush_dcache_page_asm(__pa(vfrom), vaddr);
+        preempt_enable();
+        copy_page_asm(vto, vfrom);
+}
+EXPORT_SYMBOL(copy_user_page);
+
 void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
 {
         unsigned long flags;