Re: [PATCH] xfs: log the inode on directory sf to block format change

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Oct 04, 2019 at 08:55:20AM -0400, Brian Foster wrote:
> When a directory changes from shortform (sf) to block format, the sf
> format is copied to a temporary buffer, the inode format is modified
> and the updated format filled with the dentries from the temporary
> buffer. If the inode format is modified and attempt to grow the
> inode fails (due to I/O error, for example), it is possible to
> return an error while leaving the directory in an inconsistent state
> and with an otherwise clean transaction. This results in corruption
> of the associated directory and leads to xfs_dabuf_map() errors as
> subsequent lookups cannot accurately determine the format of the
> directory. This problem is reproduced occasionally by generic/475.
> 
> The fundamental problem is that xfs_dir2_sf_to_block() changes the
> on-disk inode format without logging the inode. The inode is
> eventually logged by the bmapi layer in the common case, but error
> checking introduces the possibility of failing the high level
> request before this happens.
> 
> Update xfs_dir2_sf_to_block() to log the inode when the on-disk
> format is changed. This ensures that any subsequent errors after the
> format has changed cause the transaction to abort.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_dir2_block.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_dir2_block.c b/fs/xfs/libxfs/xfs_dir2_block.c
> index 9595ced393dc..3d1e5f6d64fd 100644
> --- a/fs/xfs/libxfs/xfs_dir2_block.c
> +++ b/fs/xfs/libxfs/xfs_dir2_block.c
> @@ -1098,6 +1098,7 @@ xfs_dir2_sf_to_block(
>  	xfs_idata_realloc(dp, -ifp->if_bytes, XFS_DATA_FORK);
>  	xfs_bmap_local_to_extents_empty(dp, XFS_DATA_FORK);
>  	dp->i_d.di_size = 0;
> +	xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);

I think the general idea looks ok, but is there any reason why we don't
log the inode in xfs_bmap_local_to_extents_empty, since it changes the
ondisk format?

Also, does xfs_attr_shortform_to_leaf have a similar problem?

--D

>  
>  	/*
>  	 * Add block 0 to the inode.
> -- 
> 2.20.1
>