From dbc446b88e7041cb1d076e51726ccee497cb6ee3 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Mon, 12 Dec 2016 16:43:55 -0800 Subject: [PATCH] mm: workingset: restore refault tracking for single-page files Shadow entries in the page cache used to be accounted behind the radix tree implementation's back in the upper bits of node->count, and the radix tree code extending a single-entry tree with a shadow entry in root->rnode would corrupt that counter. As a result, we could not put shadow entries at index 0 if the tree didn't have any other entries, and that means no refault detection for any single-page file. Now that the shadow entries are tracked natively in the radix tree's exceptional counter, this is no longer necessary. Extending and shrinking the tree from and to single entries in root->rnode now does the right thing when the entry is exceptional, remove that limitation. Link: http://lkml.kernel.org/r/20161117193244.GF23430@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Jan Kara Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index dc3e5fce0b7b..5b4dd03130da 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -167,14 +167,7 @@ static void page_cache_tree_delete(struct address_space *mapping, __radix_tree_lookup(&mapping->page_tree, page->index + i, &node, &slot); - if (!node) { - VM_BUG_ON_PAGE(nr != 1, page); - /* - * We need a node to properly account shadow - * entries. Don't plant any without. XXX - */ - shadow = NULL; - } + VM_BUG_ON_PAGE(!node && nr != 1, page); radix_tree_clear_tags(&mapping->page_tree, node, slot); __radix_tree_replace(&mapping->page_tree, node, slot, shadow,