We have a problem with a lot of emulated storage in that the driver takes a page
from get_user_pages() and does something like
kmap_atomic(page)
modify page
kunmap_atomic(page)
However, nothing has flushed the kernel cache view of the page before
the kunmap. We need a lightweight API to do this, so this new API
would specifically be for flushing the kernel cache view of a user
page which the kernel has modified. The driver would need to add
flush_kernel_dcache_page(page) before the final kunmap.
Signed-off-by: James Bottomley <[EMAIL PROTECTED]>
Index: BUILD-2.6/Documentation/cachetlb.txt
===================================================================
--- BUILD-2.6.orig/Documentation/cachetlb.txt 2006-03-20 10:52:55.000000000
-0600
+++ BUILD-2.6/Documentation/cachetlb.txt 2006-03-20 10:53:03.000000000
-0600
@@ -368,6 +368,15 @@
get_user_pages()). The default implementation is a nop (and
should remain so for all coherent architectures).
+ void flush_kernel_dcache_page(struct page *page)
+ When the kernel needs to modify a user page is has obtained
+ with kmap, it calls this function after all modifications are
+ complete (but before kunmapping it) to bring the underlying
+ page up to date. It is assumed here that the user has no
+ incoherent cached copies (i.e. the original page was obtained
+ from a mechanism like get_user_pages())
+
+
void flush_icache_range(unsigned long start, unsigned long end)
When the kernel stores into addresses that it will execute
out of (eg when loading modules), this function is called.
Index: BUILD-2.6/include/linux/highmem.h
===================================================================
--- BUILD-2.6.orig/include/linux/highmem.h 2006-03-20 10:52:55.000000000
-0600
+++ BUILD-2.6/include/linux/highmem.h 2006-03-20 10:53:03.000000000 -0600
@@ -13,6 +13,12 @@
}
#endif
+#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
+static inline void flush_kernel_dcache_page(struct page *page)
+{
+}
+#endif
+
#ifdef CONFIG_HIGHMEM
#include <asm/highmem.h>
-
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