mm: page cache: store only head pages in i_pages
Transparent Huge Pages are currently stored in i_pages as pointers to consecutive subpages. This patch changes that to storing consecutive pointers to the head page in preparation for storing huge pages more efficiently in i_pages. Large parts of this are "inspired" by Kirill's patch https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/ [willy@infradead.org: fix swapcache pages] Link: http://lkml.kernel.org/r/20190324155441.GF10344@bombadil.infradead.org [kirill@shutemov.name: hugetlb stores pages in page cache differently] Link: http://lkml.kernel.org/r/20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1 Link: http://lkml.kernel.org/r/20190307153051.18815-1-willy@infradead.org Signed-off-by: Matthew Wilcox <willy@infradead.org> Acked-by: Jan Kara <jack@suse.cz> Reviewed-by: Kirill Shutemov <kirill@shutemov.name> Reviewed-and-tested-by: Song Liu <songliubraving@fb.com> Tested-by: William Kucharski <william.kucharski@oracle.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Tested-by: Qian Cai <cai@lca.pw> Cc: Hugh Dickins <hughd@google.com> Cc: Song Liu <liu.song.a23@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds

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5fd4ca2d84
@@ -39,6 +39,7 @@ static void memfd_tag_pins(struct xa_state *xas)
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xas_for_each(xas, page, ULONG_MAX) {
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if (xa_is_value(page))
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continue;
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page = find_subpage(page, xas->xa_index);
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if (page_count(page) - page_mapcount(page) > 1)
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xas_set_mark(xas, MEMFD_TAG_PINNED);
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@@ -88,6 +89,7 @@ static int memfd_wait_for_pins(struct address_space *mapping)
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bool clear = true;
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if (xa_is_value(page))
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continue;
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page = find_subpage(page, xas.xa_index);
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if (page_count(page) - page_mapcount(page) != 1) {
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/*
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* On the last scan, we clean up all those tags
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