From patchwork Thu Mar 24 10:00:54 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 8659281 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 3145D9F44D for ; Thu, 24 Mar 2016 10:00:14 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 28A77203B4 for ; Thu, 24 Mar 2016 10:00:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29FF420373 for ; Thu, 24 Mar 2016 10:00:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756817AbcCXKAJ (ORCPT ); Thu, 24 Mar 2016 06:00:09 -0400 Received: from mga03.intel.com ([134.134.136.65]:62803 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755362AbcCXKAI (ORCPT ); Thu, 24 Mar 2016 06:00:08 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP; 24 Mar 2016 03:00:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,384,1455004800"; d="scan'208";a="72393574" Received: from spschulz-mobl2.amr.corp.intel.com (HELO thog.int.wil.cx) ([10.252.203.104]) by fmsmga004.fm.intel.com with SMTP; 24 Mar 2016 03:00:05 -0700 Received: by thog.int.wil.cx (Postfix, from userid 1000) id 330CE5F967; Thu, 24 Mar 2016 06:00:54 -0400 (EDT) Date: Thu, 24 Mar 2016 06:00:54 -0400 From: Matthew Wilcox To: Jan Kara Cc: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, NeilBrown , "Wilcox, Matthew R" , "Kirill A. Shutemov" Subject: Re: [RFC v2] [PATCH 0/10] DAX page fault locking Message-ID: <20160324100054.GA23915@linux.intel.com> References: <1458566575-28063-1-git-send-email-jack@suse.cz> <20160321174103.GP23727@linux.intel.com> <20160323150939.GK4512@quack.suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160323150939.GK4512@quack.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Wed, Mar 23, 2016 at 04:09:39PM +0100, Jan Kara wrote: > So when looking through the fixes I was wondering: Are really sibling > entries worth it? Won't the result be simpler if we just used I realised we could slightly simplify the pattern in each walker so they don't have to explicitly care about sibling entries. It ends up saving 64 bytes of text on my .config, so I think it's worth it: --- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/lib/radix-tree.c b/lib/radix-tree.c index f0f2f49..779025f 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -99,20 +99,19 @@ static inline unsigned get_sibling_offset(struct radix_tree_node *parent, return ptr - parent->slots; } -static unsigned follow_sibling(struct radix_tree_node *parent, +static unsigned rt_next_level(struct radix_tree_node *parent, struct radix_tree_node **slot, unsigned offset) { - struct radix_tree_node *node = *slot; - - if (!radix_tree_is_indirect_ptr(node)) - return offset; - - node = indirect_to_ptr(node); - if (!is_sibling_entry(parent, node)) - return offset; + void **entry = rcu_dereference_raw(parent->slots[offset]); + if (radix_tree_is_indirect_ptr(entry)) { + uintptr_t siboff = entry - parent->slots; + if (siboff < RADIX_TREE_MAP_SIZE) { + offset = siboff; + entry = rcu_dereference_raw(parent->slots[offset]); + } + } - offset = (void **)node - parent->slots; - *slot = *(void **)node; + *slot = (void *)entry; return offset; } @@ -663,6 +662,8 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index, shift = height * RADIX_TREE_MAP_SHIFT; for (;;) { + unsigned offset; + if (!node) return NULL; if (node == RADIX_TREE_RETRY) @@ -670,18 +671,14 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index, if (!radix_tree_is_indirect_ptr(node)) break; node = indirect_to_ptr(node); - if (is_sibling_entry(parent, node)) { - slot = (void **)node; - node = rcu_dereference_raw(*slot); - break; - } BUG_ON(shift == 0); shift -= RADIX_TREE_MAP_SHIFT; BUG_ON(node->shift != shift); parent = node; - slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK); - node = rcu_dereference_raw(*slot); + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + offset = rt_next_level(parent, &node, offset); + slot = parent->slots + offset; } if (nodep) @@ -764,10 +761,9 @@ void *radix_tree_tag_set(struct radix_tree_root *root, offset = (index >> shift) & RADIX_TREE_MAP_MASK; slot = indirect_to_ptr(slot); - next = slot->slots[offset]; + offset = rt_next_level(slot, &next, offset); BUG_ON(!next); - offset = follow_sibling(slot, &next, offset); if (!tag_get(slot, tag, offset)) tag_set(slot, tag, offset); slot = next; @@ -819,10 +815,9 @@ void *radix_tree_tag_clear(struct radix_tree_root *root, BUG_ON(shift != slot->shift); offset = (index >> shift) & RADIX_TREE_MAP_MASK; node = slot; - slot = slot->slots[offset]; + offset = rt_next_level(node, &slot, offset); if (slot == NULL) goto out; - offset = follow_sibling(node, &slot, offset); } if (slot == NULL) @@ -892,11 +887,11 @@ int radix_tree_tag_get(struct radix_tree_root *root, node = indirect_to_ptr(node); offset = (index >> shift) & RADIX_TREE_MAP_MASK; - next = rcu_dereference_raw(node->slots[offset]); + offset = rt_next_level(node, &next, offset); + if (!next) return 0; - - offset = follow_sibling(node, &next, offset); + /* RADIX_TREE_RETRY is OK here; the tag is still valid */ if (!tag_get(node, tag, offset)) return 0; if (!radix_tree_is_indirect_ptr(next)) @@ -988,10 +983,9 @@ restart: goto restart; } - slot = rcu_dereference_raw(node->slots[offset]); + offset = rt_next_level(node, &slot, offset); if ((slot == NULL) || (slot == RADIX_TREE_RETRY)) goto restart; - offset = follow_sibling(node, &slot, offset); if (!radix_tree_is_indirect_ptr(slot)) break; if (shift == 0)