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

[Avi Kivity <avi@xxxxxxxxxxxx>]

On 05/26/2016 04:02 PM, Christoph Hellwig wrote:
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>   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
> +        * bypasseÑ 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?