Re: [PATCH v3.2 2/3] xfs: clean up xfs_bui_item_recover iget/trans_alloc/ilock ordering

[Brian Foster <bfoster@redhat.com>]

On Sun, Oct 04, 2020 at 12:09:39PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> In most places in XFS, we have a specific order in which we gather
> resources: grab the inode, allocate a transaction, then lock the inode.
> xfs_bui_item_recover doesn't do it in that order, so fix it to be more
> consistent.  This also makes the error bailout code a bit less weird.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
> v3.2: don't remove the iunlock/irele if the defer commit succeeds
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_bmap_item.c |   41 +++++++++++++++++++++++------------------
>  1 file changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
> index c1f2cc3c42cb..852411568d14 100644
> --- a/fs/xfs/xfs_bmap_item.c
> +++ b/fs/xfs/xfs_bmap_item.c
> @@ -475,25 +475,26 @@ xfs_bui_item_recover(
>  	    (bmap->me_flags & ~XFS_BMAP_EXTENT_FLAGS))
>  		return -EFSCORRUPTED;
>  
> -	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate,
> -			XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK), 0, 0, &tp);
> -	if (error)
> -		return error;
> -
> -	budp = xfs_trans_get_bud(tp, buip);
> -
>  	/* Grab the inode. */
> -	error = xfs_iget(mp, tp, bmap->me_owner, 0, XFS_ILOCK_EXCL, &ip);
> +	error = xfs_iget(mp, NULL, bmap->me_owner, 0, 0, &ip);
>  	if (error)
> -		goto err_inode;
> +		return error;
>  
> -	error = xfs_qm_dqattach_locked(ip, false);
> +	error = xfs_qm_dqattach(ip);
>  	if (error)
> -		goto err_inode;
> +		goto err_rele;
>  
>  	if (VFS_I(ip)->i_nlink == 0)
>  		xfs_iflags_set(ip, XFS_IRECOVERY);
>  
> +	/* Allocate transaction and do the work. */
> +	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate,
> +			XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK), 0, 0, &tp);
> +	if (error)
> +		goto err_rele;
> +
> +	budp = xfs_trans_get_bud(tp, buip);
> +	xfs_ilock(ip, XFS_ILOCK_EXCL);
>  	xfs_trans_ijoin(tp, ip, 0);
>  
>  	count = bmap->me_len;
> @@ -501,7 +502,7 @@ xfs_bui_item_recover(
>  			whichfork, bmap->me_startoff, bmap->me_startblock,
>  			&count, state);
>  	if (error)
> -		goto err_inode;
> +		goto err_cancel;
>  
>  	if (count > 0) {
>  		ASSERT(bui_type == XFS_BMAP_UNMAP);
> @@ -512,17 +513,21 @@ xfs_bui_item_recover(
>  		xfs_bmap_unmap_extent(tp, ip, &irec);
>  	}
>  
> +	/* Commit transaction, which frees the transaction. */
>  	error = xfs_defer_ops_capture_and_commit(tp, capture_list);
> +	if (error)
> +		goto err_unlock;
> +
>  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
>  	xfs_irele(ip);
> -	return error;
> +	return 0;
>  
> -err_inode:
> +err_cancel:
>  	xfs_trans_cancel(tp);
> -	if (ip) {
> -		xfs_iunlock(ip, XFS_ILOCK_EXCL);
> -		xfs_irele(ip);
> -	}
> +err_unlock:
> +	xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +err_rele:
> +	xfs_irele(ip);
>  	return error;
>  }
>  
>