Messages in this thread Patch in this message | | | Subject | [PATCH 2/2] add flush_kernel_dcache_page() API | From | James Bottomley <> | Date | Tue, 21 Mar 2006 13:45:41 -0600 |
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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>
Index: BUILD-2.6/Documentation/cachetlb.txt =================================================================== --- BUILD-2.6.orig/Documentation/cachetlb.txt 2006-03-21 13:37:45.000000000 -0600 +++ BUILD-2.6/Documentation/cachetlb.txt 2006-03-21 13:37:54.000000000 -0600 @@ -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. Index: BUILD-2.6/include/linux/highmem.h =================================================================== --- BUILD-2.6.orig/include/linux/highmem.h 2006-03-21 13:37:19.000000000 -0600 +++ BUILD-2.6/include/linux/highmem.h 2006-03-21 13:37:54.000000000 -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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