From patchwork Fri Sep 9 16:34:40 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 9323979 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 ADAE260752 for ; Fri, 9 Sep 2016 16:35:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9DE3829DBE for ; Fri, 9 Sep 2016 16:35:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9283129E7B; Fri, 9 Sep 2016 16:35:15 +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=ham 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 C3DA429DBE for ; Fri, 9 Sep 2016 16:35:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753508AbcIIQfI (ORCPT ); Fri, 9 Sep 2016 12:35:08 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:54467 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753455AbcIIQfE (ORCPT ); Fri, 9 Sep 2016 12:35:04 -0400 Received: from [83.175.99.196] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.85_2 #1 (Red Hat Linux)) id 1biOlb-0005pL-GL; Fri, 09 Sep 2016 16:35:03 +0000 From: Christoph Hellwig To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@ml01.01.org Subject: [PATCH 06/10] dax: provide an iomap based fault handler Date: Fri, 9 Sep 2016 18:34:40 +0200 Message-Id: <1473438884-674-7-git-send-email-hch@lst.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1473438884-674-1-git-send-email-hch@lst.de> References: <1473438884-674-1-git-send-email-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Very similar to the existing dax_fault function, but instead of using the get_block callback we rely on the iomap_ops vector from iomap.c. That also avoids having to do two calls into the file system for write faults. Signed-off-by: Christoph Hellwig Reviewed-by: Ross Zwisler --- fs/dax.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/iomap.h | 2 + 2 files changed, 115 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index 57ad456..a170a94 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1343,4 +1343,117 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter, return done; } EXPORT_SYMBOL_GPL(iomap_dax_rw); + +/** + * iomap_dax_fault - handle a page fault on a DAX file + * @vma: The virtual memory area where the fault occurred + * @vmf: The description of the fault + * @ops: iomap ops passed from the file system + * + * When a page fault occurs, filesystems may call this helper in their fault + * or mkwrite handler for DAX files. Sssumes the caller has done all the + * necessary locking for the page fault to proceed successfully. + */ +int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, + struct iomap_ops *ops) +{ + struct address_space *mapping = vma->vm_file->f_mapping; + struct inode *inode = mapping->host; + unsigned long vaddr = (unsigned long)vmf->virtual_address; + loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; + sector_t sector; + struct iomap iomap = { 0 }; + unsigned flags = 0; + int error, major = 0; + void *entry; + + /* + * Check whether offset isn't beyond end of file now. Caller is supposed + * to hold locks serializing us with truncate / punch hole so this is + * a reliable test. + */ + if (pos >= i_size_read(inode)) + return VM_FAULT_SIGBUS; + + entry = grab_mapping_entry(mapping, vmf->pgoff); + if (IS_ERR(entry)) { + error = PTR_ERR(entry); + goto out; + } + + if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page) + flags |= IOMAP_WRITE; + + /* + * Note that we don't bother to use iomap_apply here: DAX required + * the file system block size to be equal the page size, which means + * that we never have to deal with more than a single extent here. + */ + error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap); + if (error) + goto unlock_entry; + if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { + error = -EIO; /* fs corruption? */ + goto unlock_entry; + } + + sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9); + + if (vmf->cow_page) { + switch (iomap.type) { + case IOMAP_HOLE: + case IOMAP_UNWRITTEN: + clear_user_highpage(vmf->cow_page, vaddr); + break; + case IOMAP_MAPPED: + error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE, + vmf->cow_page, vaddr); + break; + default: + WARN_ON_ONCE(1); + error = -EIO; + break; + } + + if (error) + goto unlock_entry; + if (!radix_tree_exceptional_entry(entry)) { + vmf->page = entry; + return VM_FAULT_LOCKED; + } + vmf->entry = entry; + return VM_FAULT_DAX_LOCKED; + } + + switch (iomap.type) { + case IOMAP_MAPPED: + if (iomap.flags & IOMAP_F_NEW) { + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + major = VM_FAULT_MAJOR; + } + break; + case IOMAP_UNWRITTEN: + case IOMAP_HOLE: + if (!(vmf->flags & FAULT_FLAG_WRITE)) + return dax_load_hole(mapping, entry, vmf); + default: + WARN_ON_ONCE(1); + error = -EIO; + } + + /* Filesystem should not return unwritten buffers to us! */ + error = dax_insert_mapping(mapping, iomap.bdev, sector, PAGE_SIZE, + &entry, vma, vmf); +unlock_entry: + put_locked_mapping_entry(mapping, vmf->pgoff, entry); +out: + if (error == -ENOMEM) + return VM_FAULT_OOM | major; + /* -EBUSY is fine, somebody else faulted on the same PTE */ + if (error < 0 && error != -EBUSY) + return VM_FAULT_SIGBUS | major; + return VM_FAULT_NOPAGE | major; +} +EXPORT_SYMBOL_GPL(iomap_dax_fault); #endif /* CONFIG_FS_IOMAP */ diff --git a/include/linux/iomap.h b/include/linux/iomap.h index 3d5f785..a4ef953 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -73,6 +73,8 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, struct iomap_ops *ops); int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, struct iomap_ops *ops); +int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, + struct iomap_ops *ops); int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, loff_t start, loff_t len, struct iomap_ops *ops);