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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 616F5C2D0DB for ; Tue, 28 Jan 2020 15:07:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C124207FD for ; Tue, 28 Jan 2020 15:07:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580224068; bh=zNXAL6fDLl7AhP7iPE3lYT54f7EWyhCfsBFNgifzV6w=; h=References:In-Reply-To:From:Date:Subject:To:List-ID:From; b=QQucYm1jpulZWBBtbq9jU3txTKAApGKb+nIChBJ//0VmJmW1jjqsji7v+2a4B8lX1 O03e+psVg02oRCEYG8TTHIlF7AnoE44PKUf/K/8d7hbBBTmsfZSk+1UEECPjeM5b8s lbbeTSm3XuMeFlyN46nD7Mx3kyfhoBS8vW7YsYKA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726295AbgA1PHr (ORCPT ); Tue, 28 Jan 2020 10:07:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:54586 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726057AbgA1PHr (ORCPT ); Tue, 28 Jan 2020 10:07:47 -0500 Received: from mail-ua1-f52.google.com (mail-ua1-f52.google.com [209.85.222.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6C57A207FD for ; Tue, 28 Jan 2020 15:07:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580224065; bh=zNXAL6fDLl7AhP7iPE3lYT54f7EWyhCfsBFNgifzV6w=; h=References:In-Reply-To:From:Date:Subject:To:From; b=UFIWo/HBzmZ23BU1fnj+/Tcfi/DaIjXgYxZ8akWfl8M6WpyLWyNL6lqj46cwULD1S ouudf4w7Gaed8brnDjyOklo0AuL1R9QeDAIIY37RA4UIXTI3tJHKyxRCA05+n4U8b0 EUeu++10QrB22eE5zMUE/3LlyDY2z/2ULbAjY+MQ= Received: by mail-ua1-f52.google.com with SMTP id x16so4918532uao.11 for ; Tue, 28 Jan 2020 07:07:45 -0800 (PST) X-Gm-Message-State: APjAAAVkhYFqkn1fbA3nIZ8RBJgC3ER7Kcz5kVM5GCM+lQ0xUx2irAdv jjcf3Xov0UzY1/GKmcgHBvpRsuf/s6UkMxtm86c= X-Google-Smtp-Source: APXvYqyis6uVuxtbKVsQFD/98MYYAFRToAehDSEonbswq96CKlIkmKn93+nfpkiIritoVH0aq8OmBkAXDfn9/Ranbc8= X-Received: by 2002:ab0:18a1:: with SMTP id t33mr13767933uag.123.1580224064245; Tue, 28 Jan 2020 07:07:44 -0800 (PST) MIME-Version: 1.0 References: <20200124115204.4086-1-fdmanana@kernel.org> In-Reply-To: <20200124115204.4086-1-fdmanana@kernel.org> From: Filipe Manana Date: Tue, 28 Jan 2020 15:07:32 +0000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] Btrfs: send, fix emission of invalid clone operations within the same file To: linux-btrfs Content-Type: text/plain; charset="UTF-8" Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Jan 24, 2020 at 11:54 AM wrote: > > From: Filipe Manana > > When doing an incremental send and a file has extents shared with itself > at different file offsets, it's possible for send to emit clone operations > that will fail at the destination because the source range goes beyond the > file's current size. This happens when the file size has increased in the > send snapshot, there is a hole between the shared extents and both shared > extents are at file offsets which are greater the file's size in the > parent snapshot. > > Example: > > $ mkfs.btrfs -f /dev/sdb > $ mount /dev/sdb /mnt/sdb > > $ xfs_io -f -c "pwrite -S 0xf1 0 64K" /mnt/sdb/foobar > $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/base > $ btrfs send -f /tmp/1.snap /mnt/sdb/base > > # Create a 320K extent at file offset 512K. > $ xfs_io -c "pwrite -S 0xab 512K 64K" /mnt/sdb/foobar > $ xfs_io -c "pwrite -S 0xcd 576K 64K" /mnt/sdb/foobar > $ xfs_io -c "pwrite -S 0xef 640K 64K" /mnt/sdb/foobar > $ xfs_io -c "pwrite -S 0x64 704K 64K" /mnt/sdb/foobar > $ xfs_io -c "pwrite -S 0x73 768K 64K" /mnt/sdb/foobar > > # Clone part of that 320K extent into a lower file offset (192K). > # This file offset is greater than the file's size in the parent > # snapshot (64K). Also the clone range is a bit behind the offset of > # the 320K extent so that we leave a hole between the shared extents. > $ xfs_io -c "reflink /mnt/sdb/foobar 448K 192K 192K" /mnt/sdb/foobar > > $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/incr > $ btrfs send -p /mnt/sdb/base -f /tmp/2.snap /mnt/sdb/incr > > $ mkfs.btrfs -f /dev/sdc > $ mount /dev/sdc /mnt/sdc > > $ btrfs receive -f /tmp/1.snap /mnt/sdc > $ btrfs receive -f /tmp/2.snap /mnt/sdc > ERROR: failed to clone extents to foobar: Invalid argument > > The problem is that after processing the extent at file offset 192K, send > does not issue a write operation full of zeroes for the hole between that > extent and the extent starting at file offset 520K (hole range from 384K > to 512K), this is because the hole is at an offset larger the size of the > file in the parent snapshot (384K > 64K). As a consequence the field > 'cur_inode_next_write_offset' of the send context remains with a value of > 384K when we start to process the extent at file offset 512K, which is the > value set after processing the extent at offset 192K. > > This screws up the lookup of possible extents to clone because due to an > incorrect value of 'cur_inode_next_write_offset' we can now consider > extents for cloning, in the same inode, that lie beyond the current size > of the file in the receiver of the send stream. Also, when checking if > an extent in the same file can be used for cloning, we must also check > that not only its start offset doesn't start at or beyond the current eof > of the file in the receiver but that the source range doesn't go beyond > current eof, that is we must check offset + length does not cross the > current eof, as that makes clone operations fail with -EINVAL. > > So fix this by updating 'cur_inode_next_write_offset' whenever we start > processing an extent and checking an extent's offset and length when > considering it for cloning operations. > > A test case for fstests follows soon. > > Fixes: 11f2069c113e02 ("Btrfs: send, allow clone operations within the same file") > Signed-off-by: Filipe Manana Tested-by: Craig Andrews (on behalf of Craig, see https://lore.kernel.org/linux-btrfs/f2ca887d98c1b5aacc4dde88cba74d98@integralblue.com/) > --- > fs/btrfs/send.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c > index 091e5bc8c7ea..0b42dac8a35f 100644 > --- a/fs/btrfs/send.c > +++ b/fs/btrfs/send.c > @@ -1269,7 +1269,8 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_) > * destination of the stream. > */ > if (ino == bctx->cur_objectid && > - offset >= bctx->sctx->cur_inode_next_write_offset) > + offset + bctx->extent_len > > + bctx->sctx->cur_inode_next_write_offset) > return 0; > } > > @@ -5804,6 +5805,18 @@ static int process_extent(struct send_ctx *sctx, > } > } > > + /* > + * There might be a hole between the end of the last processed extent > + * and this extent, and we may have not sent a write operation for that > + * hole because it was not needed (range is beyond eof in the parent > + * snapshot). So adjust the next write offset to the offset of this > + * extent, as we want to make sure we don't do mistakes when checking if > + * we can clone this extent from some other offset in this inode or when > + * detecting if we need to issue a truncate operation when finishing the > + * processing this inode. > + */ > + sctx->cur_inode_next_write_offset = key->offset; > + > ret = find_extent_clone(sctx, path, key->objectid, key->offset, > sctx->cur_inode_size, &found_clone); > if (ret != -ENOENT && ret < 0) > -- > 2.11.0 >