From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5958C433FF for ; Tue, 13 Aug 2019 09:14:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB8E220663 for ; Tue, 13 Aug 2019 09:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728441AbfHMJO2 (ORCPT ); Tue, 13 Aug 2019 05:14:28 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:4679 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728265AbfHMJO1 (ORCPT ); Tue, 13 Aug 2019 05:14:27 -0400 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id E4F767265375E1AB4597; Tue, 13 Aug 2019 17:14:24 +0800 (CST) Received: from architecture4.huawei.com (10.140.130.215) by smtp.huawei.com (10.3.19.208) with Microsoft SMTP Server (TLS) id 14.3.439.0; Tue, 13 Aug 2019 17:14:17 +0800 From: Gao Xiang To: linux-fsdevel , LKML , Alexander Viro CC: Greg Kroah-Hartman , Andrew Morton , Stephen Rothwell , Theodore Ts'o , Pavel Machek , David Sterba , Amir Goldstein , Christoph Hellwig , "Darrick J . Wong" , "Dave Chinner" , Jaegeuk Kim , Jan Kara , Richard Weinberger , Linus Torvalds , , , Chao Yu , Miao Xie , Li Guifu , Fang Wei , Gao Xiang Subject: [PATCH v7 12/24] erofs: introduce tagged pointer Date: Tue, 13 Aug 2019 17:13:14 +0800 Message-ID: <20190813091326.84652-13-gaoxiang25@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190813091326.84652-1-gaoxiang25@huawei.com> References: <20190813091326.84652-1-gaoxiang25@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.140.130.215] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Currently kernel has scattered tagged pointer usages hacked by hand in plain code, without a unique and portable functionset to highlight the tagged pointer itself and wrap these hacked code in order to clean up all over meaningless magic masks. This patch introduces simple generic methods to fold tags into a pointer integer. Currently it supports the last n bits of the pointer for tags, which can be selected by users. In addition, it will also be used for the upcoming EROFS filesystem, which heavily uses tagged pointer pproach to reduce extra memory allocation. Link: https://en.wikipedia.org/wiki/Tagged_pointer Signed-off-by: Gao Xiang --- fs/erofs/tagptr.h | 110 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 fs/erofs/tagptr.h diff --git a/fs/erofs/tagptr.h b/fs/erofs/tagptr.h new file mode 100644 index 000000000000..a72897c86744 --- /dev/null +++ b/fs/erofs/tagptr.h @@ -0,0 +1,110 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * A tagged pointer implementation + * + * Copyright (C) 2018 Gao Xiang + */ +#ifndef __EROFS_FS_TAGPTR_H +#define __EROFS_FS_TAGPTR_H + +#include +#include + +/* + * the name of tagged pointer types are tagptr{1, 2, 3...}_t + * avoid directly using the internal structs __tagptr{1, 2, 3...} + */ +#define __MAKE_TAGPTR(n) \ +typedef struct __tagptr##n { \ + uintptr_t v; \ +} tagptr##n##_t; + +__MAKE_TAGPTR(1) +__MAKE_TAGPTR(2) +__MAKE_TAGPTR(3) +__MAKE_TAGPTR(4) + +#undef __MAKE_TAGPTR + +extern void __compiletime_error("bad tagptr tags") + __bad_tagptr_tags(void); + +extern void __compiletime_error("bad tagptr type") + __bad_tagptr_type(void); + +/* fix the broken usage of "#define tagptr2_t tagptr3_t" by users */ +#define __tagptr_mask_1(ptr, n) \ + __builtin_types_compatible_p(typeof(ptr), struct __tagptr##n) ? \ + (1UL << (n)) - 1 : + +#define __tagptr_mask(ptr) (\ + __tagptr_mask_1(ptr, 1) ( \ + __tagptr_mask_1(ptr, 2) ( \ + __tagptr_mask_1(ptr, 3) ( \ + __tagptr_mask_1(ptr, 4) ( \ + __bad_tagptr_type(), 0))))) + +/* generate a tagged pointer from a raw value */ +#define tagptr_init(type, val) \ + ((typeof(type)){ .v = (uintptr_t)(val) }) + +/* + * directly cast a tagged pointer to the native pointer type, which + * could be used for backward compatibility of existing code. + */ +#define tagptr_cast_ptr(tptr) ((void *)(tptr).v) + +/* encode tagged pointers */ +#define tagptr_fold(type, ptr, _tags) ({ \ + const typeof(_tags) tags = (_tags); \ + if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(type))) \ + __bad_tagptr_tags(); \ +tagptr_init(type, (uintptr_t)(ptr) | tags); }) + +/* decode tagged pointers */ +#define tagptr_unfold_ptr(tptr) \ + ((void *)((tptr).v & ~__tagptr_mask(tptr))) + +#define tagptr_unfold_tags(tptr) \ + ((tptr).v & __tagptr_mask(tptr)) + +/* operations for the tagger pointer */ +#define tagptr_eq(_tptr1, _tptr2) ({ \ + typeof(_tptr1) tptr1 = (_tptr1); \ + typeof(_tptr2) tptr2 = (_tptr2); \ + (void)(&tptr1 == &tptr2); \ +(tptr1).v == (tptr2).v; }) + +/* lock-free CAS operation */ +#define tagptr_cmpxchg(_ptptr, _o, _n) ({ \ + typeof(_ptptr) ptptr = (_ptptr); \ + typeof(_o) o = (_o); \ + typeof(_n) n = (_n); \ + (void)(&o == &n); \ + (void)(&o == ptptr); \ +tagptr_init(o, cmpxchg(&ptptr->v, o.v, n.v)); }) + +/* wrap WRITE_ONCE if atomic update is needed */ +#define tagptr_replace_tags(_ptptr, tags) ({ \ + typeof(_ptptr) ptptr = (_ptptr); \ + *ptptr = tagptr_fold(*ptptr, tagptr_unfold_ptr(*ptptr), tags); \ +*ptptr; }) + +#define tagptr_set_tags(_ptptr, _tags) ({ \ + typeof(_ptptr) ptptr = (_ptptr); \ + const typeof(_tags) tags = (_tags); \ + if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \ + __bad_tagptr_tags(); \ + ptptr->v |= tags; \ +*ptptr; }) + +#define tagptr_clear_tags(_ptptr, _tags) ({ \ + typeof(_ptptr) ptptr = (_ptptr); \ + const typeof(_tags) tags = (_tags); \ + if (__builtin_constant_p(tags) && (tags & ~__tagptr_mask(*ptptr))) \ + __bad_tagptr_tags(); \ + ptptr->v &= ~tags; \ +*ptptr; }) + +#endif /* __EROFS_FS_TAGPTR_H */ + -- 2.17.1