From patchwork Fri Jul 10 20:29:22 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Wilcox, Matthew R" X-Patchwork-Id: 6768411 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 36120C05AC for ; Fri, 10 Jul 2015 20:32:23 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 171152078E for ; Fri, 10 Jul 2015 20:32:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC36D20787 for ; Fri, 10 Jul 2015 20:32:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933281AbbGJUaO (ORCPT ); Fri, 10 Jul 2015 16:30:14 -0400 Received: from mga14.intel.com ([192.55.52.115]:11060 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933145AbbGJU3s (ORCPT ); Fri, 10 Jul 2015 16:29:48 -0400 Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga103.fm.intel.com with ESMTP; 10 Jul 2015 13:29:38 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,449,1432623600"; d="scan'208";a="762160482" Received: from qwang4-mobl2.ccr.corp.intel.com (HELO thog.int.wil.cx) ([10.252.194.226]) by orsmga002.jf.intel.com with SMTP; 10 Jul 2015 13:29:35 -0700 Received: by thog.int.wil.cx (Postfix, from userid 1000) id A6B3460EDE; Fri, 10 Jul 2015 16:29:33 -0400 (EDT) From: Matthew Wilcox To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Matthew Wilcox Subject: [PATCH 07/10] dax: Add huge page fault support Date: Fri, 10 Jul 2015 16:29:22 -0400 Message-Id: <1436560165-8943-8-git-send-email-matthew.r.wilcox@intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1436560165-8943-1-git-send-email-matthew.r.wilcox@intel.com> References: <1436560165-8943-1-git-send-email-matthew.r.wilcox@intel.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Wilcox This is the support code for DAX-enabled filesystems to allow them to provide huge pages in response to faults. Signed-off-by: Matthew Wilcox --- Documentation/filesystems/dax.txt | 7 +- fs/dax.c | 152 ++++++++++++++++++++++++++++++++++++++ include/linux/dax.h | 14 ++++ 3 files changed, 170 insertions(+), 3 deletions(-) diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt index 7af2851..7bde640 100644 --- a/Documentation/filesystems/dax.txt +++ b/Documentation/filesystems/dax.txt @@ -60,9 +60,10 @@ Filesystem support consists of - implementing the direct_IO address space operation, and calling dax_do_io() instead of blockdev_direct_IO() if S_DAX is set - implementing an mmap file operation for DAX files which sets the - VM_MIXEDMAP flag on the VMA, and setting the vm_ops to include handlers - for fault and page_mkwrite (which should probably call dax_fault() and - dax_mkwrite(), passing the appropriate get_block() callback) + VM_MIXEDMAP and VM_HUGEPAGE flags on the VMA, and setting the vm_ops to + include handlers for fault, pmd_fault and page_mkwrite (which should + probably call dax_fault(), dax_pmd_fault() and dax_mkwrite(), passing the + appropriate get_block() callback) - calling dax_truncate_page() instead of block_truncate_page() for DAX files - calling dax_zero_page_range() instead of zero_user() for DAX files - ensuring that there is sufficient locking between reads, writes, diff --git a/fs/dax.c b/fs/dax.c index c3e21cc..20cf3b0 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -484,6 +484,158 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, } EXPORT_SYMBOL_GPL(dax_fault); +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +/* + * The 'colour' (ie low bits) within a PMD of a page offset. This comes up + * more often than one might expect in the below function. + */ +#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1) + +int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, unsigned int flags, get_block_t get_block, + dax_iodone_t complete_unwritten) +{ + struct file *file = vma->vm_file; + struct address_space *mapping = file->f_mapping; + struct inode *inode = mapping->host; + struct buffer_head bh; + unsigned blkbits = inode->i_blkbits; + unsigned long pmd_addr = address & PMD_MASK; + bool write = flags & FAULT_FLAG_WRITE; + long length; + void *kaddr; + pgoff_t size, pgoff; + sector_t block, sector; + unsigned long pfn; + int result = 0; + + /* Fall back to PTEs if we're going to COW */ + if (write && !(vma->vm_flags & VM_SHARED)) + return VM_FAULT_FALLBACK; + /* If the PMD would extend outside the VMA */ + if (pmd_addr < vma->vm_start) + return VM_FAULT_FALLBACK; + if ((pmd_addr + PMD_SIZE) > vma->vm_end) + return VM_FAULT_FALLBACK; + + pgoff = ((pmd_addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (pgoff >= size) + return VM_FAULT_SIGBUS; + /* If the PMD would cover blocks out of the file */ + if ((pgoff | PG_PMD_COLOUR) >= size) + return VM_FAULT_FALLBACK; + + memset(&bh, 0, sizeof(bh)); + block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); + + bh.b_size = PMD_SIZE; + length = get_block(inode, block, &bh, write); + if (length) + return VM_FAULT_SIGBUS; + i_mmap_lock_read(mapping); + + /* + * If the filesystem isn't willing to tell us the length of a hole, + * just fall back to PTEs. Calling get_block 512 times in a loop + * would be silly. + */ + if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) + goto fallback; + + /* Guard against a race with truncate */ + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (pgoff >= size) { + result = VM_FAULT_SIGBUS; + goto out; + } + if ((pgoff | PG_PMD_COLOUR) >= size) + goto fallback; + + if (is_huge_zero_pmd(*pmd)) + unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0); + + if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) { + bool set; + spinlock_t *ptl; + struct mm_struct *mm = vma->vm_mm; + struct page *zero_page = get_huge_zero_page(); + if (unlikely(!zero_page)) + goto fallback; + + ptl = pmd_lock(mm, pmd); + set = set_huge_zero_page(NULL, mm, vma, pmd_addr, pmd, + zero_page); + spin_unlock(ptl); + result = VM_FAULT_NOPAGE; + } else { + sector = bh.b_blocknr << (blkbits - 9); + length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, + bh.b_size); + if (length < 0) { + result = VM_FAULT_SIGBUS; + goto out; + } + if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) + goto fallback; + + if (buffer_unwritten(&bh) || buffer_new(&bh)) { + int i; + for (i = 0; i < PTRS_PER_PMD; i++) + clear_page(kaddr + i * PAGE_SIZE); + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + result |= VM_FAULT_MAJOR; + } + + result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write); + } + + out: + i_mmap_unlock_read(mapping); + + if (buffer_unwritten(&bh)) + complete_unwritten(&bh, !(result & VM_FAULT_ERROR)); + + return result; + + fallback: + count_vm_event(THP_FAULT_FALLBACK); + result = VM_FAULT_FALLBACK; + goto out; +} +EXPORT_SYMBOL_GPL(__dax_pmd_fault); + +/** + * dax_pmd_fault - handle a PMD fault on a DAX file + * @vma: The virtual memory area where the fault occurred + * @vmf: The description of the fault + * @get_block: The filesystem method used to translate file offsets to blocks + * + * When a page fault occurs, filesystems may call this helper in their + * pmd_fault handler for DAX files. + */ +int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, unsigned int flags, get_block_t get_block, + dax_iodone_t complete_unwritten) +{ + int result; + struct super_block *sb = file_inode(vma->vm_file)->i_sb; + + if (flags & FAULT_FLAG_WRITE) { + sb_start_pagefault(sb); + file_update_time(vma->vm_file); + } + result = __dax_pmd_fault(vma, address, pmd, flags, get_block, + complete_unwritten); + if (flags & FAULT_FLAG_WRITE) + sb_end_pagefault(sb); + + return result; +} +EXPORT_SYMBOL_GPL(dax_pmd_fault); +#endif /* CONFIG_TRANSPARENT_HUGEPAGES */ + /** * dax_pfn_mkwrite - handle first write to DAX page * @vma: The virtual memory area where the fault occurred diff --git a/include/linux/dax.h b/include/linux/dax.h index 9b51f9d..b415e52 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -14,6 +14,20 @@ int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t, dax_iodone_t); int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t, dax_iodone_t); +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *, + unsigned int flags, get_block_t, dax_iodone_t); +int __dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *, + unsigned int flags, get_block_t, dax_iodone_t); +#else +static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, unsigned int flags, get_block_t gb, + dax_iodone_t di) +{ + return VM_FAULT_FALLBACK; +} +#define __dax_pmd_fault dax_pmd_fault +#endif int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *); #define dax_mkwrite(vma, vmf, gb, iod) dax_fault(vma, vmf, gb, iod) #define __dax_mkwrite(vma, vmf, gb, iod) __dax_fault(vma, vmf, gb, iod)