Re: [PATCH v8 07/16] xfs: add xfs_remount_ro() helper

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

On Fri, Nov 01, 2019 at 03:50:39PM +0800, Ian Kent wrote:
> Factor the remount read only code into a helper to simplify the
> subsequent change from the super block method .remount_fs to the
> mount-api fs_context_operations method .reconfigure.
> 
> Signed-off-by: Ian Kent <raven@themaw.net>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

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

--D

> ---
>  fs/xfs/xfs_super.c |   73 +++++++++++++++++++++++++++++++---------------------
>  1 file changed, 43 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 6eaa1b05897a..bdf6c069e3ea 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1246,6 +1246,47 @@ xfs_remount_rw(
>  	return 0;
>  }
>  
> +static int
> +xfs_remount_ro(
> +	struct xfs_mount	*mp)
> +{
> +	int error;
> +
> +	/*
> +	 * Cancel background eofb scanning so it cannot race with the final
> +	 * log force+buftarg wait and deadlock the remount.
> +	 */
> +	xfs_stop_block_reaping(mp);
> +
> +	/* Get rid of any leftover CoW reservations... */
> +	error = xfs_icache_free_cowblocks(mp, NULL);
> +	if (error) {
> +		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> +		return error;
> +	}
> +
> +	/* Free the per-AG metadata reservation pool. */
> +	error = xfs_fs_unreserve_ag_blocks(mp);
> +	if (error) {
> +		xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> +		return error;
> +	}
> +
> +	/*
> +	 * Before we sync the metadata, we need to free up the reserve block
> +	 * pool so that the used block count in the superblock on disk is
> +	 * correct at the end of the remount. Stash the current* reserve pool
> +	 * size so that if we get remounted rw, we can return it to the same
> +	 * size.
> +	 */
> +	xfs_save_resvblks(mp);
> +
> +	xfs_quiesce_attr(mp);
> +	mp->m_flags |= XFS_MOUNT_RDONLY;
> +
> +	return 0;
> +}
> +
>  STATIC int
>  xfs_fs_remount(
>  	struct super_block	*sb,
> @@ -1316,37 +1357,9 @@ xfs_fs_remount(
>  
>  	/* rw -> ro */
>  	if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (*flags & SB_RDONLY)) {
> -		/*
> -		 * Cancel background eofb scanning so it cannot race with the
> -		 * final log force+buftarg wait and deadlock the remount.
> -		 */
> -		xfs_stop_block_reaping(mp);
> -
> -		/* Get rid of any leftover CoW reservations... */
> -		error = xfs_icache_free_cowblocks(mp, NULL);
> -		if (error) {
> -			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> -			return error;
> -		}
> -
> -		/* Free the per-AG metadata reservation pool. */
> -		error = xfs_fs_unreserve_ag_blocks(mp);
> -		if (error) {
> -			xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> +		error = xfs_remount_ro(mp);
> +		if (error)
>  			return error;
> -		}
> -
> -		/*
> -		 * Before we sync the metadata, we need to free up the reserve
> -		 * block pool so that the used block count in the superblock on
> -		 * disk is correct at the end of the remount. Stash the current
> -		 * reserve pool size so that if we get remounted rw, we can
> -		 * return it to the same size.
> -		 */
> -		xfs_save_resvblks(mp);
> -
> -		xfs_quiesce_attr(mp);
> -		mp->m_flags |= XFS_MOUNT_RDONLY;
>  	}
>  
>  	return 0;
>