From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:46112 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726727AbeH3UNA (ORCPT ); Thu, 30 Aug 2018 16:13:00 -0400 From: Eric Sandeen Subject: [PATCH, RFC] xfs: re-enable FIBMAP on reflink; disable for swap Message-ID: <2eb759e5-2faa-67fd-5c16-c1d8edc42d02@redhat.com> Date: Thu, 30 Aug 2018 11:10:05 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs Cc: Christoph Hellwig We disabled FIBMAP/bmap calls for reflinked files because swap will then writes directly to the blocks, bypassing COW mechanisms, and breaking copy on write. As noted in commit db1327b, this restriction also breaks bootloaders that want to use the FIBMAP ioctl. Rather than disabling the entire mapping interface for everyone just because swapon may abuse the info, teach xfs_iomap_swapfile_activate() to reject activation for reflinked files, and re-enable the FIBMAP interface. Signed-off-by: Eric Sandeen --- yes, other FIBMAP users could also abuse this information, but disallowing mapping because somebody might do something dumb with it seems very heavy handed... thoughts? diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 8eb3ba3d4d00..b75a7f37bdd9 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -1382,15 +1382,10 @@ xfs_vm_bmap( trace_xfs_vm_bmap(ip); /* - * The swap code (ab-)uses ->bmap to get a block mapping and then - * bypasses the file system for actual I/O. We really can't allow - * that on reflinks inodes, so we have to skip out here. And yes, - * 0 is the magic code for a bmap error. - * * Since we don't pass back blockdev info, we can't return bmap - * information for rt files either. + * information for rt files. */ - if (xfs_is_reflink_inode(ip) || XFS_IS_REALTIME_INODE(ip)) + if (XFS_IS_REALTIME_INODE(ip)) return 0; return iomap_bmap(mapping, block, &xfs_iomap_ops); } @@ -1477,7 +1472,13 @@ xfs_iomap_swapfile_activate( struct file *swap_file, sector_t *span) { - sis->bdev = xfs_find_bdev_for_inode(file_inode(swap_file)); + struct inode *inode = file_inode(swap_file); + + /* Cannot allow swap to write directly to reflinked files/blocks */ + if (xfs_is_reflink_inode(XFS_I(inode))) + return -EOPNOTSUPP; + + sis->bdev = xfs_find_bdev_for_inode(inode); return iomap_swapfile_activate(sis, swap_file, span, &xfs_iomap_ops); }