Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753261AbbEKGeA (ORCPT ); Mon, 11 May 2015 02:34:00 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:45768 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752552AbbEKGd5 (ORCPT ); Mon, 11 May 2015 02:33:57 -0400 From: "Aneesh Kumar K.V" To: Andrew Morton Cc: mpe@ellerman.id.au, paulus@samba.org, benh@kernel.crashing.org, kirill.shutemov@linux.intel.com, aarcange@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org 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> User-Agent: Notmuch/0.19+103~g294bb6d (http://notmuchmail.org) Emacs/24.4.1 (x86_64-pc-linux-gnu) 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 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051106-0017-0000-0000-00000135156C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2594 Lines: 68 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/