From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com [202.81.31.142]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 631D61A0010 for ; Mon, 11 May 2015 16:33:56 +1000 (AEST) Received: from /spool/local by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 11 May 2015 16:33:55 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 6E0B92BB0047 for ; Mon, 11 May 2015 16:33:53 +1000 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t4B6Xj5M18481334 for ; Mon, 11 May 2015 16:33:53 +1000 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t4B6XJaZ008418 for ; Mon, 11 May 2015 16:33:20 +1000 From: "Aneesh Kumar K.V" To: Andrew Morton Subject: Re: [PATCH V2 1/2] mm/thp: Split out pmd collpase flush into a seperate functions In-Reply-To: <20150508152428.4326eaaae99b74fa53c96f23@linux-foundation.org> References: <1430983408-24924-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20150508152428.4326eaaae99b74fa53c96f23@linux-foundation.org> Date: Mon, 11 May 2015 12:02:52 +0530 Message-ID: <87wq0f4oa3.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Cc: aarcange@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paulus@samba.org, linuxppc-dev@lists.ozlabs.org, kirill.shutemov@linux.intel.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Andrew Morton writes: > On Thu, 7 May 2015 12:53:27 +0530 "Aneesh Kumar K.V" wrote: > >> After this patch pmdp_* functions operate only on hugepage pte, >> and not on regular pmd_t values pointing to page table. >> > > The patch looks like a pretty safe no-op for non-powerpc? That is correct. I also updated the commit message mm/thp: Split out pmd collpase flush into a seperate functions Architectures like ppc64 [1] need to do special things while clearing pmd before a collapse. For them this operation is largely different from a normal hugepage pte clear. Hence add a separate function to clear pmd before collapse. After this patch pmdp_* functions operate only on hugepage pte, and not on regular pmd_t values pointing to page table. [1] ppc64 needs to invalidate all the normal page pte mappings we already have inserted in the hardware hash page table. But before doing that we need to make sure there are no parallel hash page table insert going on. So we need to do a kick_all_cpus_sync() before flushing the older hash table entries. By moving this to a separate function we capture these details and mention how it is different from a hugepage pte clear. > >> --- a/arch/powerpc/include/asm/pgtable-ppc64.h >> +++ b/arch/powerpc/include/asm/pgtable-ppc64.h >> @@ -576,6 +576,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr, >> extern void pmdp_splitting_flush(struct vm_area_struct *vma, >> unsigned long address, pmd_t *pmdp); >> >> +#define __HAVE_ARCH_PMDP_COLLAPSE_FLUSH >> +extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, >> + unsigned long address, pmd_t *pmdp); >> + > > The fashionable way of doing this is > > extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, > unsigned long address, pmd_t *pmdp); > #define pmdp_collapse_flush pmdp_collapse_flush > > then, elsewhere, > > #ifndef pmdp_collapse_flush > static inline pmd_t pmdp_collapse_flush(...) {} > #define pmdp_collapse_flush pmdp_collapse_flush > #endif > > It avoids introducing a second (ugly) symbol into the kernel. Ok updated to the above style. The reason I used the earlier style was because of similar usages in asm-generic/pgtable.h -aneesh