From patchwork Wed Jun 14 17:22:09 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ross Zwisler X-Patchwork-Id: 9787041 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id EA5156038E for ; Wed, 14 Jun 2017 17:22:43 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D02AB27E5A for ; Wed, 14 Jun 2017 17:22:43 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C4CCC283AE; Wed, 14 Jun 2017 17:22:43 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 613D427E5A for ; Wed, 14 Jun 2017 17:22:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752723AbdFNRWj (ORCPT ); Wed, 14 Jun 2017 13:22:39 -0400 Received: from mga06.intel.com ([134.134.136.31]:16236 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752562AbdFNRWg (ORCPT ); Wed, 14 Jun 2017 13:22:36 -0400 Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP; 14 Jun 2017 10:22:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,341,1493708400"; d="scan'208";a="99492158" Received: from theros.lm.intel.com ([10.232.112.77]) by orsmga002.jf.intel.com with ESMTP; 14 Jun 2017 10:22:18 -0700 From: Ross Zwisler To: Andrew Morton , linux-kernel@vger.kernel.org Cc: Ross Zwisler , "Darrick J. Wong" , "Theodore Ts'o" , Alexander Viro , Andreas Dilger , Christoph Hellwig , Dan Williams , Dave Hansen , Ingo Molnar , Jan Kara , Jonathan Corbet , Matthew Wilcox , Steven Rostedt , linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org Subject: [PATCH v2 1/3] mm: add vm_insert_mixed_mkwrite() Date: Wed, 14 Jun 2017 11:22:09 -0600 Message-Id: <20170614172211.19820-2-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170614172211.19820-1-ross.zwisler@linux.intel.com> References: <20170614172211.19820-1-ross.zwisler@linux.intel.com> Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP To be able to use the common 4k zero page in DAX we need to have our PTE fault path look more like our PMD fault path where a PTE entry can be marked as dirty and writeable as it is first inserted, rather than waiting for a follow-up dax_pfn_mkwrite() => finish_mkwrite_fault() call. Right now we can rely on having a dax_pfn_mkwrite() call because we can distinguish between these two cases in do_wp_page(): case 1: 4k zero page => writable DAX storage case 2: read-only DAX storage => writeable DAX storage This distinction is made by via vm_normal_page(). vm_normal_page() returns false for the common 4k zero page, though, just as it does for DAX ptes. Instead of special casing the DAX + 4k zero page case, we will simplify our DAX PTE page fault sequence so that it matches our DAX PMD sequence, and get rid of dax_pfn_mkwrite() completely. This means that insert_pfn() needs to follow the lead of insert_pfn_pmd() and allow us to pass in a 'mkwrite' flag. If 'mkwrite' is set insert_pfn() will do the work that was previously done by wp_page_reuse() as part of the dax_pfn_mkwrite() call path. Signed-off-by: Ross Zwisler --- include/linux/mm.h | 2 ++ mm/memory.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 47 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index b892e95..0ea79e6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2296,6 +2296,8 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn, pgprot_t pgprot); int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, pfn_t pfn); +int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn); int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len); diff --git a/mm/memory.c b/mm/memory.c index 2e65df1..38d7c4f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1646,7 +1646,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, EXPORT_SYMBOL(vm_insert_page); static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, - pfn_t pfn, pgprot_t prot) + pfn_t pfn, pgprot_t prot, bool mkwrite) { struct mm_struct *mm = vma->vm_mm; int retval; @@ -1658,7 +1658,7 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, if (!pte) goto out; retval = -EBUSY; - if (!pte_none(*pte)) + if (!pte_none(*pte) && !mkwrite) goto out_unlock; /* Ok, finally just insert the thing.. */ @@ -1666,6 +1666,12 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr, entry = pte_mkdevmap(pfn_t_pte(pfn, prot)); else entry = pte_mkspecial(pfn_t_pte(pfn, prot)); + + if (mkwrite) { + entry = pte_mkyoung(entry); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + } + set_pte_at(mm, addr, pte, entry); update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */ @@ -1736,7 +1742,8 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV)); - ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot); + ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot, + false); return ret; } @@ -1772,10 +1779,44 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, page = pfn_to_page(pfn_t_to_pfn(pfn)); return insert_page(vma, addr, page, pgprot); } - return insert_pfn(vma, addr, pfn, pgprot); + return insert_pfn(vma, addr, pfn, pgprot, false); } EXPORT_SYMBOL(vm_insert_mixed); +int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn) +{ + pgprot_t pgprot = vma->vm_page_prot; + + BUG_ON(!(vma->vm_flags & VM_MIXEDMAP)); + + if (addr < vma->vm_start || addr >= vma->vm_end) + return -EFAULT; + + track_pfn_insert(vma, &pgprot, pfn); + + /* + * If we don't have pte special, then we have to use the pfn_valid() + * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must* + * refcount the page if pfn_valid is true (hence insert_page rather + * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP + * without pte special, it would there be refcounted as a normal page. + */ + if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) { + struct page *page; + + /* + * At this point we are committed to insert_page() + * regardless of whether the caller specified flags that + * result in pfn_t_has_page() == false. + */ + page = pfn_to_page(pfn_t_to_pfn(pfn)); + return insert_page(vma, addr, page, pgprot); + } + return insert_pfn(vma, addr, pfn, pgprot, true); +} +EXPORT_SYMBOL(vm_insert_mixed_mkwrite); + /* * maps a range of physical memory into the requested pages. the old * mappings are removed. any references to nonexistent pages results