From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752678AbcCKVNM (ORCPT ); Fri, 11 Mar 2016 16:13:12 -0500 Received: from mga04.intel.com ([192.55.52.120]:58631 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752556AbcCKVNI (ORCPT ); Fri, 11 Mar 2016 16:13:08 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,321,1455004800"; d="scan'208";a="922021490" From: Matthew Wilcox To: Dan Williams Cc: Matthew Wilcox , linux-nvdimm@ml01.01.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@linux.intel.com Subject: [PATCH 1/3] pfn_t: Change the encoding Date: Fri, 11 Mar 2016 16:13:02 -0500 Message-Id: <1457730784-9890-2-git-send-email-matthew.r.wilcox@intel.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: <1457730784-9890-1-git-send-email-matthew.r.wilcox@intel.com> References: <1457730784-9890-1-git-send-email-matthew.r.wilcox@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org By moving the flag bits to the bottom, we encourage commonality between SGs with pages and those using pfn_t. We can also then insert a pfn_t into a radix tree, as it uses the same two bits for indirect & exceptional indicators. Signed-off-by: Matthew Wilcox --- include/linux/pfn_t.h | 41 ++++++++++++++++++++++++++++++----------- 1 file changed, 30 insertions(+), 11 deletions(-) diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h index 9499481..37c596c 100644 --- a/include/linux/pfn_t.h +++ b/include/linux/pfn_t.h @@ -8,16 +8,34 @@ * PFN_SG_LAST - pfn references a page and is the last scatterlist entry * PFN_DEV - pfn is not covered by system memmap by default * PFN_MAP - pfn has a dynamic page mapping established by a device driver + * + * Note that the bottom two bits in the pfn_t match the bottom two bits in the + * scatterlist so sg_is_chain() and sg_is_last() work. These bits are also + * used by the radix tree for its own purposes, but a PFN cannot be in both a + * radix tree and a scatterlist simultaneously. If a PFN is moved between the + * two usages, care should be taken to clear/set these bits appropriately. */ -#define PFN_FLAGS_MASK (((u64) ~PAGE_MASK) << (BITS_PER_LONG_LONG - PAGE_SHIFT)) -#define PFN_SG_CHAIN (1ULL << (BITS_PER_LONG_LONG - 1)) -#define PFN_SG_LAST (1ULL << (BITS_PER_LONG_LONG - 2)) -#define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3)) -#define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4)) +#define PFN_FLAG_BITS 4 +#define PFN_FLAGS_MASK ((1 << PFN_FLAG_BITS) - 1) +#define __PFN_MAX ((1 << (BITS_PER_LONG - PFN_FLAG_BITS)) - 1) +#define PFN_SG_CHAIN 0x01UL +#define PFN_SG_LAST 0x02UL +#define PFN_SG_MASK (PFN_SG_CHAIN | PFN_SG_LAST) +#define PFN_DEV 0x04UL +#define PFN_MAP 0x08UL + +#if 0 +#define PFN_T_BUG_ON(x) BUG_ON(x) +#else +#define PFN_T_BUG_ON(x) BUILD_BUG_ON_INVALID(x) +#endif static inline pfn_t __pfn_to_pfn_t(unsigned long pfn, u64 flags) { - pfn_t pfn_t = { .val = pfn | (flags & PFN_FLAGS_MASK), }; + pfn_t pfn_t = { .val = (pfn << PFN_FLAG_BITS) | flags }; + + PFN_T_BUG_ON(pfn & ~__PFN_MAX); + PFN_T_BUG_ON(flags & ~PFN_FLAGS_MASK); return pfn_t; } @@ -28,6 +46,12 @@ static inline pfn_t pfn_to_pfn_t(unsigned long pfn) return __pfn_to_pfn_t(pfn, 0); } +static inline unsigned long pfn_t_to_pfn(pfn_t pfn) +{ + unsigned long v = pfn.val; + return v >> PFN_FLAG_BITS; +} + extern pfn_t phys_to_pfn_t(phys_addr_t addr, u64 flags); static inline bool pfn_t_has_page(pfn_t pfn) @@ -35,11 +59,6 @@ static inline bool pfn_t_has_page(pfn_t pfn) return (pfn.val & PFN_MAP) == PFN_MAP || (pfn.val & PFN_DEV) == 0; } -static inline unsigned long pfn_t_to_pfn(pfn_t pfn) -{ - return pfn.val & ~PFN_FLAGS_MASK; -} - static inline struct page *pfn_t_to_page(pfn_t pfn) { if (pfn_t_has_page(pfn)) -- 2.7.0