Re: [PATCH 7/8] xfs: refactor unmount record writing

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

On Tue, Mar 24, 2020 at 06:44:58PM +0100, Christoph Hellwig wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Separate out the unmount record writing from the rest of the
> ticket and log state futzing necessary to make it work. This is
> a no-op, just makes the code cleaner and places the unmount record
> formatting and writing alongside the commit record formatting and
> writing code.
> 
> We can also get rid of the ticket flag clearing before the
> xlog_write() call because it no longer cares about the state of
> XLOG_TIC_INITED.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Brian Foster <bfoster@redhat.com>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_log.c | 65 +++++++++++++++++++++++++++---------------------
>  1 file changed, 37 insertions(+), 28 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index a173b5925d1b..1d6ed696f717 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -471,6 +471,36 @@ xfs_log_reserve(
>   *		marked as with WANT_SYNC.
>   */
>  
> +/*
> + * Write out an unmount record using the ticket provided. We have to account for
> + * the data space used in the unmount ticket as this write is not done from a
> + * transaction context that has already done the accounting for us.
> + */
> +static int
> +xlog_write_unmount_record(
> +	struct xlog		*log,
> +	struct xlog_ticket	*ticket,
> +	xfs_lsn_t		*lsn,
> +	uint			flags)
> +{
> +	struct xfs_unmount_log_format ulf = {
> +		.magic = XLOG_UNMOUNT_TYPE,
> +	};
> +	struct xfs_log_iovec reg = {
> +		.i_addr = &ulf,
> +		.i_len = sizeof(ulf),
> +		.i_type = XLOG_REG_TYPE_UNMOUNT,
> +	};
> +	struct xfs_log_vec vec = {
> +		.lv_niovecs = 1,
> +		.lv_iovecp = &reg,
> +	};
> +
> +	/* account for space used by record data */
> +	ticket->t_curr_res -= sizeof(ulf);
> +	return xlog_write(log, &vec, ticket, lsn, NULL, flags);
> +}
> +
>  static bool
>  __xlog_state_release_iclog(
>  	struct xlog		*log,
> @@ -795,32 +825,14 @@ xlog_wait_on_iclog(
>  }
>  
>  /*
> - * Final log writes as part of unmount.
> - *
> - * Mark the filesystem clean as unmount happens.  Note that during relocation
> - * this routine needs to be executed as part of source-bag while the
> - * deallocation must not be done until source-end.
> + * Mark the filesystem clean by writing an unmount record to the head of the
> + * log.
>   */
> -
> -/* Actually write the unmount record to disk. */
>  static void
> -xfs_log_write_unmount_record(
> -	struct xfs_mount	*mp)
> +xlog_unmount_write(
> +	struct xlog		*log)
>  {
> -	/* the data section must be 32 bit size aligned */
> -	struct xfs_unmount_log_format magic = {
> -		.magic = XLOG_UNMOUNT_TYPE,
> -	};
> -	struct xfs_log_iovec reg = {
> -		.i_addr = &magic,
> -		.i_len = sizeof(magic),
> -		.i_type = XLOG_REG_TYPE_UNMOUNT,
> -	};
> -	struct xfs_log_vec vec = {
> -		.lv_niovecs = 1,
> -		.lv_iovecp = &reg,
> -	};
> -	struct xlog		*log = mp->m_log;
> +	struct xfs_mount	*mp = log->l_mp;
>  	struct xlog_in_core	*iclog;
>  	struct xlog_ticket	*tic = NULL;
>  	xfs_lsn_t		lsn;
> @@ -844,10 +856,7 @@ xfs_log_write_unmount_record(
>  		flags &= ~XLOG_UNMOUNT_TRANS;
>  	}
>  
> -	/* remove inited flag, and account for space used */
> -	tic->t_flags = 0;
> -	tic->t_curr_res -= sizeof(magic);
> -	error = xlog_write(log, &vec, tic, &lsn, NULL, flags);
> +	error = xlog_write_unmount_record(log, tic, &lsn, flags);
>  	/*
>  	 * At this point, we're umounting anyway, so there's no point in
>  	 * transitioning log state to IOERROR. Just continue...
> @@ -913,7 +922,7 @@ xfs_log_unmount_write(
>  	if (XLOG_FORCED_SHUTDOWN(log))
>  		return;
>  	xfs_log_unmount_verify_iclog(log);
> -	xfs_log_write_unmount_record(mp);
> +	xlog_unmount_write(log);
>  }
>  
>  /*
> -- 
> 2.25.1
>