From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:42630 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752196AbeEOHg1 (ORCPT ); Tue, 15 May 2018 03:36:27 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 9C5C6ADFF for ; Tue, 15 May 2018 07:36:26 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH 1/2] btrfs: inode: Don't compress if NODATASUM or NODATACOW set Date: Tue, 15 May 2018 15:36:21 +0800 Message-Id: <20180515073622.18732-2-wqu@suse.com> In-Reply-To: <20180515073622.18732-1-wqu@suse.com> References: <20180515073622.18732-1-wqu@suse.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: As btrfs(5) specified: Note If nodatacow or nodatasum are enabled, compression is disabled. If NODATASUM or NODATACOW set, we should not compress the extent. Normally NODATACOW is detected properly in run_delalloc_range() so compression won't happen for NODATACOW. However for NODATASUM we don't have any check, and it can cause compressed extent without csum pretty easily, just by: ------ mkfs.btrfs -f $dev mount $dev $mnt -o nodatasum touch $mnt/foobar mount -o remount,datasum,compress $mnt xfs_io -f -c "pwrite 0 128K" $mnt/foobar ------ And in fact, we have bug report about corrupted compressed extent without proper data checksum so even RAID1 can't recover the corruption. (https://bugzilla.kernel.org/show_bug.cgi?id=199707) Running compression without proper checksum could cause more damage when corruption happens, so there is no need to allow compression for NODATACSUM. Reported-by: James Harvey Signed-off-by: Qu Wenruo --- fs/btrfs/inode.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index d241285a0d2a..dbef3f404559 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -396,6 +396,14 @@ static inline int inode_need_compress(struct inode *inode, u64 start, u64 end) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + /* + * Btrfs doesn't support compression without csum or CoW. + * This should have the highest priority. + */ + if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW || + BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) + return 0; + /* force compress */ if (btrfs_test_opt(fs_info, FORCE_COMPRESS)) return 1; -- 2.17.0