From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: 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@xxxxxxxxxxx Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff -puN mm/filemap.c~mm-workingset-restore-refault-tracking-for-single-page-files mm/filemap.c --- a/mm/filemap.c~mm-workingset-restore-refault-tracking-for-single-page-files +++ a/mm/filemap.c @@ -167,14 +167,7 @@ static void page_cache_tree_delete(struc __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, _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
