[RESEND PATCH] ARM: Handle user space mapped pages in flush_kernel_dcache_page
From: Simon Baatz <hidden>
Date: 2012-07-28 08:41:54
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Commit f8b63c1 made flush_kernel_dcache_page a no-op assuming that the pages it needs to handle are kernel mapped only. However, for example when doing direct I/O, pages with user space mappings may occur. Thus, continue to do lazy flushing if there are no user space mappings. Otherwise, flush the kernel cache lines directly. Signed-off-by: Simon Baatz <redacted> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <redacted> --- Hi, a while ago I sent the patch above to fix a data corruption problem on VIVT architectures (and probably VIPT aliasing). There has been a bit of discussion with Catalin, but there was no real conclusion on how to proceed. (See http://www.spinics.net/lists/arm-kernel/msg176913.html for the original post) The case is not hit too often apparently; the ingredients are PIO (like) driver, use of flush_kernel_dcache_page(), and direct I/O. However, there is at least one real world example (running lvm2 on top of an encrypted block device using mv_cesa on Kirkwood) that does not work at all because of this problem. - Simon arch/arm/include/asm/cacheflush.h | 4 ++++ arch/arm/mm/flush.c | 22 ++++++++++++++++++++++ 2 files changed, 26 insertions(+)
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 004c1bc..91ddc70 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h@@ -303,6 +303,10 @@ static inline void flush_anon_page(struct vm_area_struct *vma, #define ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE static inline void flush_kernel_dcache_page(struct page *page) { + extern void __flush_kernel_dcache_page(struct page *); + /* highmem pages are always flushed upon kunmap already */ + if ((cache_is_vivt() || cache_is_vipt_aliasing()) && !PageHighMem(page)) + __flush_kernel_dcache_page(page); } #define flush_dcache_mmap_lock(mapping) \
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 7745854..bcba3a9 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c@@ -192,6 +192,28 @@ void __flush_dcache_page(struct address_space *mapping, struct page *page) page->index << PAGE_CACHE_SHIFT); } +/* + * Ensure cache coherency for kernel mapping of this page. + * + * If the page only exists in the page cache and there are no user + * space mappings, this is a no-op since the page was already marked + * dirty@creation. Otherwise, we need to flush the dirty kernel + * cache lines directly. + * + * We can assume that the page is no high mem page, see + * flush_kernel_dcache_page. + */ +void __flush_kernel_dcache_page(struct page *page) +{ + struct address_space *mapping; + + mapping = page_mapping(page); + + if (!mapping || mapping_mapped(mapping)) + __cpuc_flush_dcache_area(page_address(page), PAGE_SIZE); +} +EXPORT_SYMBOL(__flush_kernel_dcache_page); + static void __flush_dcache_aliases(struct address_space *mapping, struct page *page) { struct mm_struct *mm = current->active_mm;
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1.7.9.5