From patchwork Tue Mar 13 13:26:28 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 10278845 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id DE3966038F for ; Tue, 13 Mar 2018 13:37:53 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CFCCA28714 for ; Tue, 13 Mar 2018 13:37:53 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C4A78287EA; Tue, 13 Mar 2018 13:37:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6AF7B28714 for ; Tue, 13 Mar 2018 13:37:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932616AbeCMNgZ (ORCPT ); Tue, 13 Mar 2018 09:36:25 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:35546 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932651AbeCMN1F (ORCPT ); Tue, 13 Mar 2018 09:27:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=References:In-Reply-To:Message-Id: Date:Subject:Cc:To:From:Sender:Reply-To:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=gyb9Qm4DfyPt3dYM4uU9XVaSLgvPmG8u7M2kgi/AW98=; b=Zb4sYGdCFt1Rv32iFSYGmH28y mLnjtRY1YhyhXtN0RzcdX6kbUZ7TrgnEliu/RLCIcdUV7KCHSv3AmHF5JlIQlBos9qpvzimSyHb/0 cNqJtGMVBz/aGmi65nJ+JZvyA2aEoLaqVOuuN6l7tnkk9sBvyYkGEROFYQicin+1nD5Q57qy3KnOY lNrK33OlXSOigzfmhZywn27MD2MY7MACrRtrMQ/v1rH5q3omPWwlJxwQpYvo83Dksm/btwK40WDXb zpTXI9nXYmeXrHsKmhFQnUdNvCYvjcYg7mUcf2isAapMH8KIzU002D6M+88J7h3Dvt15Esai0Lx8X S5OFF6USw==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1evjxI-0004lI-0f; Tue, 13 Mar 2018 13:27:04 +0000 From: Matthew Wilcox To: Andrew Morton Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Ryusuke Konishi , linux-nilfs@vger.kernel.org Subject: [PATCH v9 50/61] memfd: Convert shmem_tag_pins to XArray Date: Tue, 13 Mar 2018 06:26:28 -0700 Message-Id: <20180313132639.17387-51-willy@infradead.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180313132639.17387-1-willy@infradead.org> References: <20180313132639.17387-1-willy@infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Wilcox Simplify the locking by taking the spinlock while we walk the tree on the assumption that many acquires and releases of the lock will be worse than holding the lock for a (potentially) long time. We could replicate the same locking behaviour with the xarray, but would have to be careful that the xa_node wasn't RCU-freed under us before we took the lock. Signed-off-by: Matthew Wilcox --- mm/memfd.c | 43 ++++++++++++++++++------------------------- 1 file changed, 18 insertions(+), 25 deletions(-) diff --git a/mm/memfd.c b/mm/memfd.c index 4cf7401cb09c..3b299d72df78 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -21,7 +21,7 @@ #include /* - * We need a tag: a new tag would expand every radix_tree_node by 8 bytes, + * We need a tag: a new tag would expand every xa_node by 8 bytes, * so reuse a tag which we firmly believe is never set or cleared on shmem. */ #define SHMEM_TAG_PINNED PAGECACHE_TAG_TOWRITE @@ -29,35 +29,28 @@ static void shmem_tag_pins(struct address_space *mapping) { - struct radix_tree_iter iter; - void __rcu **slot; - pgoff_t start; + XA_STATE(xas, &mapping->i_pages, 0); struct page *page; + unsigned int tagged = 0; lru_add_drain(); - start = 0; - rcu_read_lock(); - - radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) { - page = radix_tree_deref_slot(slot); - if (!page || radix_tree_exception(page)) { - if (radix_tree_deref_retry(page)) { - slot = radix_tree_iter_retry(&iter); - continue; - } - } else if (page_count(page) - page_mapcount(page) > 1) { - xa_lock_irq(&mapping->i_pages); - radix_tree_tag_set(&mapping->i_pages, iter.index, - SHMEM_TAG_PINNED); - xa_unlock_irq(&mapping->i_pages); - } - if (need_resched()) { - slot = radix_tree_iter_resume(slot, &iter); - cond_resched_rcu(); - } + xas_lock_irq(&xas); + xas_for_each(&xas, page, ULONG_MAX) { + if (xa_is_value(page)) + continue; + if (page_count(page) - page_mapcount(page) > 1) + xas_set_tag(&xas, SHMEM_TAG_PINNED); + + if (++tagged % XA_CHECK_SCHED) + continue; + + xas_pause(&xas); + xas_unlock_irq(&xas); + cond_resched(); + xas_lock_irq(&xas); } - rcu_read_unlock(); + xas_unlock_irq(&xas); } /*