From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE8EEC43381 for ; Wed, 27 Mar 2019 17:54:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7302E2075C for ; Wed, 27 Mar 2019 17:54:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="FklUO/rN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728934AbfC0Ryb (ORCPT ); Wed, 27 Mar 2019 13:54:31 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:43906 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727695AbfC0Ryb (ORCPT ); Wed, 27 Mar 2019 13:54:31 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2RHrprg074789; Wed, 27 Mar 2019 17:54:24 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2018-07-02; bh=vw//IQeYnYLQIo5JWn3HtytOeZHORkr5RWBAi0SrpHs=; b=FklUO/rN9dnppJlaCfkVDflNOuzwna/QpPgtFgpVhA3xhoTYRorGFtJxp2tL/naBweuO WPCRnUiPqif0Nn2PJBMNfpRGViKCucw5V1dU1r+I67FXAKpW5/XD0u5N8HzTRRoCQpfk +mDIUCws+8z9+GCWIJdHsJrnvTzZBxqlz/aU+iN3BpVKI58nn5W31TzX9bHA5oZkLmsL 4lu86QhhiEYmaWZCSh0f+MoIjrDMG4yK5N1dfSXVC+Sw6MDeV2U0j9h0jkE5s+rY62u/ F/krXpcK6YJtLpxTDGB9d/3zbld78MjV4p+MCc99eN7gIeWdm9phKsNGZYtVuk9vJBMX 9g== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by userp2120.oracle.com with ESMTP id 2re6djj848-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 27 Mar 2019 17:54:23 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x2RHsHl2001153 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 27 Mar 2019 17:54:17 GMT Received: from abhmp0022.oracle.com (abhmp0022.oracle.com [141.146.116.28]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2RHsGCg024017; Wed, 27 Mar 2019 17:54:16 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 27 Mar 2019 10:54:16 -0700 Date: Wed, 27 Mar 2019 10:54:14 -0700 From: "Darrick J. Wong" To: Goldwyn Rodrigues Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Goldwyn Rodrigues Subject: Re: [PATCH 04/15] dax: Introduce IOMAP_F_COW for copy-on-write Message-ID: <20190327175414.GB1172@magnolia> References: <20190326190301.32365-1-rgoldwyn@suse.de> <20190326190301.32365-5-rgoldwyn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326190301.32365-5-rgoldwyn@suse.de> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9207 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903270126 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Mar 26, 2019 at 02:02:50PM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > The IOMAP_F_COW is a flag to notify dax that it needs to copy > the data from iomap->cow_addr to iomap->addr, if the start/end > of I/O are not page aligned. > > This also introduces dax_to_dax_copy() which performs a copy > from one part of the device to another, to a maximum of one page. > > Question: Using iomap.cow_addr == 0 means the CoW is to be copied > (or memset) from a hole. Would this be better handled through a flag? > > Signed-off-by: Goldwyn Rodrigues > --- > fs/dax.c | 36 ++++++++++++++++++++++++++++++++++++ > include/linux/iomap.h | 3 +++ > 2 files changed, 39 insertions(+) > > diff --git a/fs/dax.c b/fs/dax.c > index ca0671d55aa6..e254535dd830 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1051,6 +1051,28 @@ static bool dax_range_is_aligned(struct block_device *bdev, > return true; > } > > +static void dax_to_dax_copy(struct iomap *iomap, loff_t pos, void *daddr, > + size_t len) > +{ > + loff_t blk_start, blk_pg; > + void *saddr; > + ssize_t map_len; > + > + /* A zero address is a hole. */ > + if (iomap->cow_addr == 0) { > + memset(daddr, 0, len); > + return; > + } > + > + blk_start = iomap->cow_addr + pos - iomap->cow_pos; > + blk_pg = round_down(blk_start, PAGE_SIZE); > + > + map_len = dax_direct_access(iomap->dax_dev, PHYS_PFN(blk_pg), PAGE_SIZE, > + &saddr, NULL); > + saddr += blk_start - blk_pg; > + memcpy(daddr, saddr, len); > +} > + > int __dax_zero_page_range(struct block_device *bdev, > struct dax_device *dax_dev, sector_t sector, > unsigned int offset, unsigned int size) > @@ -1143,6 +1165,20 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > break; > } > > + if (iomap->flags & IOMAP_F_COW) { > + loff_t pg_end = round_up(end, PAGE_SIZE); > + /* > + * Copy the first part of the page > + * Note: we pass offset as length > + */ > + if (offset) > + dax_to_dax_copy(iomap, pos - offset, kaddr, offset); > + > + /* Copy the last part of the range */ > + if (end < pg_end) > + dax_to_dax_copy(iomap, end, kaddr + offset + length, pg_end - end); > + } > + > map_len = PFN_PHYS(map_len); > kaddr += offset; > map_len -= offset; > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 0fefb5455bda..391785de1428 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h Probably a good idea to cc the iomap maintainers on this (entire patchset)... --D > @@ -35,6 +35,7 @@ struct vm_fault; > #define IOMAP_F_NEW 0x01 /* blocks have been newly allocated */ > #define IOMAP_F_DIRTY 0x02 /* uncommitted metadata */ > #define IOMAP_F_BUFFER_HEAD 0x04 /* file system requires buffer heads */ > +#define IOMAP_F_COW 0x08 /* cow before write */ > > /* > * Flags that only need to be reported for IOMAP_REPORT requests: > @@ -59,6 +60,8 @@ struct iomap { > u64 length; /* length of mapping, bytes */ > u16 type; /* type of mapping */ > u16 flags; /* flags for mapping */ > + u64 cow_addr; /* read address to perform CoW */ > + loff_t cow_pos; /* file offset of cow_addr */ > struct block_device *bdev; /* block device for I/O */ > struct dax_device *dax_dev; /* dax_dev for dax operations */ > void *inline_data; > -- > 2.16.4 >