From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f43.google.com (mail-wg0-f43.google.com [74.125.82.43]) by kanga.kvack.org (Postfix) with ESMTP id 0AEFC6B0150 for ; Fri, 22 May 2015 03:36:00 -0400 (EDT) Received: by wgbgq6 with SMTP id gq6so9394542wgb.3 for ; Fri, 22 May 2015 00:35:59 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id cu9si5436171wib.124.2015.05.22.00.35.58 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 22 May 2015 00:35:58 -0700 (PDT) Date: Fri, 22 May 2015 09:35:59 +0200 (CEST) From: Thomas Gleixner Subject: Re: [PATCH v9 7/10] x86, mm, asm: Add WT support to set_page_memtype() In-Reply-To: <1431551151-19124-8-git-send-email-toshi.kani@hp.com> Message-ID: References: <1431551151-19124-1-git-send-email-toshi.kani@hp.com> <1431551151-19124-8-git-send-email-toshi.kani@hp.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Toshi Kani Cc: hpa@zytor.com, mingo@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-nvdimm@ml01.01.org, jgross@suse.com, stefan.bader@canonical.com, luto@amacapital.net, hmh@hmh.eng.br, yigal@plexistor.com, konrad.wilk@oracle.com, Elliott@hp.com, mcgrof@suse.com, hch@lst.de On Wed, 13 May 2015, Toshi Kani wrote: > + * X86 PAT uses page flags arch_1 and uncached together to keep track of > + * memory type of pages that have backing page struct. X86 PAT supports 4 > + * different memory types, _PAGE_CACHE_MODE_WT, _PAGE_CACHE_MODE_WC, > + * _PAGE_CACHE_MODE_UC_MINUS and _PAGE_CACHE_MODE_WB where page's memory > + * type has not been changed from its default. This is a horrible sentence. * X86 PAT supports 4 different memory types: * - _PAGE_CACHE_MODE_WB * - _PAGE_CACHE_MODE_WC * - _PAGE_CACHE_MODE_UC_MINUS * - _PAGE_CACHE_MODE_WT * * _PAGE_CACHE_MODE_WB is the default type. */ Hmm? > * Note we do not support _PAGE_CACHE_MODE_UC here. This can be removed as it is completely redundant. > */ > > -#define _PGMT_DEFAULT 0 > +#define _PGMT_WB 0 /* default */ We just established two lines above that this is the default > #define _PGMT_WC (1UL << PG_arch_1) > #define _PGMT_UC_MINUS (1UL << PG_uncached) > -#define _PGMT_WB (1UL << PG_uncached | 1UL << PG_arch_1) > +#define _PGMT_WT (1UL << PG_uncached | 1UL << PG_arch_1) > #define _PGMT_MASK (1UL << PG_uncached | 1UL << PG_arch_1) > #define _PGMT_CLEAR_MASK (~_PGMT_MASK) > > @@ -88,14 +88,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg) > { > unsigned long pg_flags = pg->flags & _PGMT_MASK; > > - if (pg_flags == _PGMT_DEFAULT) > - return -1; > + if (pg_flags == _PGMT_WB) > + return _PAGE_CACHE_MODE_WB; > else if (pg_flags == _PGMT_WC) > return _PAGE_CACHE_MODE_WC; > else if (pg_flags == _PGMT_UC_MINUS) > return _PAGE_CACHE_MODE_UC_MINUS; > else > - return _PAGE_CACHE_MODE_WB; > + return _PAGE_CACHE_MODE_WT; > } > > static inline void set_page_memtype(struct page *pg, > @@ -112,11 +112,12 @@ static inline void set_page_memtype(struct page *pg, > case _PAGE_CACHE_MODE_UC_MINUS: > memtype_flags = _PGMT_UC_MINUS; > break; > - case _PAGE_CACHE_MODE_WB: > - memtype_flags = _PGMT_WB; > + case _PAGE_CACHE_MODE_WT: > + memtype_flags = _PGMT_WT; > break; > + case _PAGE_CACHE_MODE_WB: > default: > - memtype_flags = _PGMT_DEFAULT; > + memtype_flags = _PGMT_WB; /* default */ What's the value of that comment? default: /* default */ Aside of the, please do not use tail comments. They make code harder to parse. > /* > * For RAM pages, we use page flags to mark the pages with appropriate type. > - * The page flags are limited to three types, WB, WC and UC-. > - * WT and WP requests fail with -EINVAL, and UC gets redirected to UC-. > + * The page flags are limited to four types, WB (default), WC, WT and UC-. > + * WP request fails with -EINVAL, and UC gets redirected to UC-. > + * A new memtype can only be set to the default memtype WB. I have no idea what that line means. > @@ -582,13 +583,6 @@ static enum page_cache_mode lookup_memtype(u64 paddr) > struct page *page; > page = pfn_to_page(paddr >> PAGE_SHIFT); > rettype = get_page_memtype(page); return get_page_memtype(page); And while you are at it please add the missing newline between the variable declaration and code. Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org