[PATCH] rmap 3 arches + mapping_mapped
From: Hugh Dickins <hugh@veritas.com> Some arches refer to page->mapping for their dcache flushing: use page_mapping(page) for safety, to avoid confusion on anon pages, which will store a different pointer there - though in most cases flush_dcache_page is being applied to pagecache pages. arm has a useful mapping_mapped macro: move that to generic, and add mapping_writably_mapped, to avoid explicit list_empty checks on i_mmap and i_mmap_shared in several places. Very tempted to add page_mapped(page) tests, perhaps along with the mapping_writably_mapped tests in do_generic_mapping_read and do_shmem_file_read, to cut down on wasted flush_dcache effort; but the serialization is not obvious, too unsafe to do in a hurry.
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