[PATCH] Add flush_kernel_dcache_page() API
We have a problem in a lot of emulated storage in that it 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 <James.Bottomley@SteelEye.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/Documentation/cachetlb.txt b/Documentation/cachetlb.txt
index 1f312a9..53245c4 100644
--- a/Documentation/cachetlb.txt
+++ b/Documentation/cachetlb.txt
@@ -371,6 +371,18 @@
architectures). For incoherent architectures, it should flush
the cache of the page at vmaddr in the current user process.
+ 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()). The default
+ implementation is a nop and should remain so on all coherent
+ architectures. On incoherent architectures, this should flush
+ the kernel cache for page (using page_address(page)).
+
+
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.
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7bd2593..892c4ea 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -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>