From patchwork Thu Mar 10 19:18:45 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 8559581 Return-Path: X-Original-To: patchwork-linux-nvdimm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id BCD13C0555 for ; Thu, 10 Mar 2016 19:18:42 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id CFDC92037C for ; Thu, 10 Mar 2016 19:18:41 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 444A520381 for ; Thu, 10 Mar 2016 19:18:40 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 47C9B1A1F61; Thu, 10 Mar 2016 11:18:54 -0800 (PST) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id C305F1A1EF8 for ; Thu, 10 Mar 2016 11:18:52 -0800 (PST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 0BF6AAC32; Thu, 10 Mar 2016 19:18:34 +0000 (UTC) Received: by quack.suse.cz (Postfix, from userid 1000) id 223F88251E; Thu, 10 Mar 2016 20:18:57 +0100 (CET) From: Jan Kara To: linux-fsdevel@vger.kernel.org Subject: [PATCH 02/12] radix-tree: make 'indirect' bit available to exception entries. Date: Thu, 10 Mar 2016 20:18:45 +0100 Message-Id: <1457637535-21633-3-git-send-email-jack@suse.cz> X-Mailer: git-send-email 2.6.2 In-Reply-To: <1457637535-21633-1-git-send-email-jack@suse.cz> References: <1457637535-21633-1-git-send-email-jack@suse.cz> Cc: Jan Kara , linux-nvdimm@lists.01.org, NeilBrown , "Wilcox, Matthew R" X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_NONE, 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 From: NeilBrown A pointer to a radix_tree_node will always have the 'exception' bit cleared, so if the exception bit is set the value cannot be an indirect pointer. Thus it is safe to make the 'indirect bit' available to store extra information in exception entries. This patch adds a 'PTR_MASK' and a value is only treated as an indirect (pointer) entry the 2 ls-bits are '01'. The change in radix-tree.c ensures the stored value still looks like an indirect pointer, and saves a load as well. We could swap the two bits and so keep all the exectional bits contigious. But I have other plans for that bit.... Signed-off-by: NeilBrown Signed-off-by: Jan Kara --- include/linux/radix-tree.h | 11 +++++++++-- lib/radix-tree.c | 2 +- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 968150ab8a1c..450c12b546b7 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -40,8 +40,13 @@ * Indirect pointer in fact is also used to tag the last pointer of a node * when it is shrunk, before we rcu free the node. See shrink code for * details. + * + * To allow an exception entry to only lose one bit, we ignore + * the INDIRECT bit when the exception bit is set. So an entry is + * indirect if the least significant 2 bits are 01. */ #define RADIX_TREE_INDIRECT_PTR 1 +#define RADIX_TREE_INDIRECT_MASK 3 /* * A common use of the radix tree is to store pointers to struct pages; * but shmem/tmpfs needs also to store swap entries in the same tree: @@ -53,7 +58,8 @@ static inline int radix_tree_is_indirect_ptr(void *ptr) { - return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); + return ((unsigned long)ptr & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR; } /*** radix-tree API starts here ***/ @@ -221,7 +227,8 @@ static inline void *radix_tree_deref_slot_protected(void **pslot, */ static inline int radix_tree_deref_retry(void *arg) { - return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); + return unlikely(((unsigned long)arg & RADIX_TREE_INDIRECT_MASK) + == RADIX_TREE_INDIRECT_PTR); } /** diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 6b79e9026e24..37d4643ab5c0 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1305,7 +1305,7 @@ static inline void radix_tree_shrink(struct radix_tree_root *root) * to force callers to retry. */ if (root->height == 0) - *((unsigned long *)&to_free->slots[0]) |= + *((unsigned long *)&to_free->slots[0]) = RADIX_TREE_INDIRECT_PTR; radix_tree_node_free(to_free);