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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 EE8BEC10F06 for ; Tue, 26 Mar 2019 19:03:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE7C320823 for ; Tue, 26 Mar 2019 19:03:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732560AbfCZTD0 (ORCPT ); Tue, 26 Mar 2019 15:03:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:36958 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732504AbfCZTD0 (ORCPT ); Tue, 26 Mar 2019 15:03:26 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CD4D2AEE6; Tue, 26 Mar 2019 19:03:24 +0000 (UTC) From: Goldwyn Rodrigues To: linux-btrfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, Goldwyn Rodrigues Subject: [PATCH 04/15] dax: Introduce IOMAP_F_COW for copy-on-write Date: Tue, 26 Mar 2019 14:02:50 -0500 Message-Id: <20190326190301.32365-5-rgoldwyn@suse.de> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190326190301.32365-1-rgoldwyn@suse.de> References: <20190326190301.32365-1-rgoldwyn@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 @@ -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