forked from Minki/linux
ARM: ZERO_PAGE: Avoid flush_dcache_page() for zero page
The zero page is read-only, and has its cache state cleared during boot. No further maintanence for this page is required. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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@ -151,7 +151,14 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
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if (!pfn_valid(pfn))
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return;
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/*
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* The zero page is never written to, so never has any dirty
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* cache lines, and therefore never needs to be flushed.
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*/
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page = pfn_to_page(pfn);
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if (page == ZERO_PAGE(0))
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return;
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mapping = page_mapping(page);
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#ifndef CONFIG_SMP
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if (test_and_clear_bit(PG_dcache_dirty, &page->flags))
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@ -189,7 +189,16 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
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*/
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void flush_dcache_page(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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struct address_space *mapping;
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/*
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* The zero page is never written to, so never has any dirty
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* cache lines, and therefore never needs to be flushed.
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*/
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if (page == ZERO_PAGE(0))
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return;
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mapping = page_mapping(page);
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#ifndef CONFIG_SMP
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if (!PageHighMem(page) && mapping && !mapping_mapped(mapping))
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@ -1036,7 +1036,7 @@ void __init paging_init(struct machine_desc *mdesc)
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*/
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zero_page = alloc_bootmem_low_pages(PAGE_SIZE);
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empty_zero_page = virt_to_page(zero_page);
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flush_dcache_page(empty_zero_page);
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__flush_dcache_page(NULL, empty_zero_page);
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}
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/*
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