[PATCH] xfs: fail ->bmap for reflink inodes

[Darrick J. Wong]

On Fri, May 27, 2016 at 08:32:18PM +0300, Avi Kivity wrote:
> On 05/26/2016 04:02 PM, Christoph Hellwig wrote:
> >Signed-off-by: Christoph Hellwig <hch at lst.de>
> >---
> >  fs/xfs/xfs_aops.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> >diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> >index a955552..d053a9e 100644
> >--- a/fs/xfs/xfs_aops.c
> >+++ b/fs/xfs/xfs_aops.c
> >@@ -1829,6 +1829,17 @@ 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);
> 
> Don't you also have to prevent a swapfile from being reflinked after it's
> bmapped?  Or is that already taken care of?

Already taken care of, at least for XFS.

--D