From db1327b16c2b24e28d1e5899bced89db9ae6538e Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Mon, 3 Oct 2016 09:11:36 -0700 Subject: [PATCH] xfs: report shared extent mappings to userspace correctly Report shared extents through the iomap interface so that FIEMAP flags shared blocks accurately. Have xfs_vm_bmap return zero for reflinked files because the bmap-based swap code requires static block mappings, which is incompatible with copy on write. NOTE: Existing userspace bmap users such as lilo will have the same problem with reflink files. Signed-off-by: Christoph Hellwig Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_aops.c | 11 +++++++++++ fs/xfs/xfs_iomap.c | 12 +++++++++++- 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index f6f5bbc39dda..2f4a15ec9ee9 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -1508,6 +1508,17 @@ xfs_vm_bmap( trace_xfs_vm_bmap(XFS_I(inode)); xfs_ilock(ip, XFS_IOLOCK_SHARED); + + /* + * The swap code (ab-)uses ->bmap to get a block mapping and then + * bypasseѕ 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.. + */ + if (xfs_is_reflink_inode(ip)) { + xfs_iunlock(ip, XFS_IOLOCK_SHARED); + return 0; + } filemap_write_and_wait(mapping); xfs_iunlock(ip, XFS_IOLOCK_SHARED); return generic_block_bmap(mapping, block, xfs_get_blocks); diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index ad6939df9680..765849ed9b70 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -961,6 +961,7 @@ xfs_file_iomap_begin( struct xfs_mount *mp = ip->i_mount; struct xfs_bmbt_irec imap; xfs_fileoff_t offset_fsb, end_fsb; + bool shared, trimmed; int nimaps = 1, error = 0; unsigned lockmode; @@ -989,7 +990,14 @@ xfs_file_iomap_begin( end_fsb = XFS_B_TO_FSB(mp, offset + length); error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap, - &nimaps, XFS_BMAPI_ENTIRE); + &nimaps, 0); + if (error) { + xfs_iunlock(ip, lockmode); + return error; + } + + /* Trim the mapping to the nearest shared extent boundary. */ + error = xfs_reflink_trim_around_shared(ip, &imap, &shared, &trimmed); if (error) { xfs_iunlock(ip, lockmode); return error; @@ -1028,6 +1036,8 @@ xfs_file_iomap_begin( } xfs_bmbt_to_iomap(ip, iomap, &imap); + if (shared) + iomap->flags |= IOMAP_F_SHARED; return 0; } -- 2.20.1