Re: [PATCH 02/10] xfs: set lv_bytes in xlog_write_one_vec

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Nov 12, 2025 at 01:14:18PM +0100, Christoph Hellwig wrote:
> lv_bytes is mostly just use by the CIL code, but has crept into the
> low-level log writing code to decide on a full or partial iclog
> write.  Ensure it is valid even for the special log writes that don't
> go through the CIL by initializing it in xlog_write_one_vec.
> 
> Note that even without this fix, the checkpoint commits would never
> trigger a partial iclog write, as they have no payload beyond the
> opheader.
> 
> The unmount record on the other hand could in theory trigger a an
> overflow of the iclog, but given that is has never been seen in
> the wild this has probably been masked by the small size of it
> and the fact that the unmount process does multiple log forces
> before writing the unmount record and we thus usually operate on
> an empty or almost empty iclog.
> 
> Fixes: 110dc24ad2ae ("xfs: log vector rounding leaks log space")
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_log.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index ed83a0e3578e..382c55f4d8d2 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -858,14 +858,15 @@ xlog_write_one_vec(
>  	struct xfs_log_vec	lv = {
>  		.lv_niovecs	= 1,
>  		.lv_iovecp	= reg,
> +		.lv_bytes	= reg->i_len,
>  	};
>  	LIST_HEAD		(lv_chain);
>  
>  	/* account for space used by record data */
> -	ticket->t_curr_res -= reg->i_len;
> +	ticket->t_curr_res -= lv.lv_bytes;
>  
>  	list_add(&lv.lv_list, &lv_chain);
> -	return xlog_write(log, ctx, &lv_chain, ticket, reg->i_len);
> +	return xlog_write(log, ctx, &lv_chain, ticket, lv.lv_bytes);
>  }
>  
>  /*
> -- 
> 2.47.3
> 
>