Re: [PATCH v2 7/9] xfs: have getfsmap fall back to the freesp btrees when rmap is not present

[Brian Foster <bfoster@redhat.com>]

On Wed, Mar 01, 2017 at 06:29:53PM -0800, Darrick J. Wong wrote:
> If the reverse-mapping btree isn't available, fall back to the
> free space btrees to provide partial reverse mapping information.
> The online scrub tool can make use of even partial information to
> speed up the data block scan.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

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

> v2: various refactorings, fix array pointer passing
> ---
>  fs/xfs/xfs_fsmap.c |   72 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 69 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
> index 2fd05a0..b855984 100644
> --- a/fs/xfs/xfs_fsmap.c
> +++ b/fs/xfs/xfs_fsmap.c
> @@ -40,6 +40,7 @@
>  #include "xfs_fsmap.h"
>  #include "xfs_refcount.h"
>  #include "xfs_refcount_btree.h"
> +#include "xfs_alloc_btree.h"
>  
>  /* Convert an xfs_fsmap to an fsmap. */
>  void
> @@ -158,6 +159,9 @@ xfs_fsmap_owner_from_rmap(
>  	case XFS_RMAP_OWN_COW:
>  		dest->fmr_owner = XFS_FMR_OWN_COW;
>  		break;
> +	case XFS_RMAP_OWN_NULL:	/* "free" */
> +		dest->fmr_owner = XFS_FMR_OWN_FREE;
> +		break;
>  	default:
>  		return -EFSCORRUPTED;
>  	}
> @@ -378,6 +382,30 @@ xfs_getfsmap_rtdev_helper(
>  	return xfs_getfsmap_helper(cur->bc_tp, info, rec, rec_daddr);
>  }
>  
> +/* Transform a bnobt irec into a fsmap */
> +STATIC int
> +xfs_getfsmap_datadev_bnobt_helper(
> +	struct xfs_btree_cur		*cur,
> +	struct xfs_alloc_rec_incore	*rec,
> +	void				*priv)
> +{
> +	struct xfs_mount		*mp = cur->bc_mp;
> +	struct xfs_getfsmap_info	*info = priv;
> +	struct xfs_rmap_irec		irec;
> +	xfs_daddr_t			rec_daddr;
> +
> +	rec_daddr = XFS_AGB_TO_DADDR(mp, cur->bc_private.a.agno,
> +			rec->ar_startblock);
> +
> +	irec.rm_startblock = rec->ar_startblock;
> +	irec.rm_blockcount = rec->ar_blockcount;
> +	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
> +	irec.rm_offset = 0;
> +	irec.rm_flags = 0;
> +
> +	return xfs_getfsmap_helper(cur->bc_tp, info, &irec, rec_daddr);
> +}
> +
>  /* Set rmap flags based on the getfsmap flags */
>  static void
>  xfs_getfsmap_set_irec_flags(
> @@ -588,6 +616,43 @@ xfs_getfsmap_datadev_rmapbt(
>  			xfs_getfsmap_datadev_rmapbt_query, NULL);
>  }
>  
> +/* Actually query the bno btree. */
> +STATIC int
> +xfs_getfsmap_datadev_bnobt_query(
> +	struct xfs_trans		*tp,
> +	struct xfs_getfsmap_info	*info,
> +	struct xfs_btree_cur		**curpp,
> +	void				*priv)
> +{
> +	struct xfs_alloc_rec_incore	*key = priv;
> +
> +	/* Report any gap at the end of the last AG. */
> +	if (info->last)
> +		return xfs_getfsmap_datadev_bnobt_helper(*curpp, &key[1], info);
> +
> +	/* Allocate cursor for this AG and query_range it. */
> +	*curpp = xfs_allocbt_init_cursor(tp->t_mountp, tp, info->agf_bp,
> +			info->agno, XFS_BTNUM_BNO);
> +	key->ar_startblock = info->low.rm_startblock;
> +	key[1].ar_startblock = info->high.rm_startblock;
> +	return xfs_alloc_query_range(*curpp, key, &key[1],
> +			xfs_getfsmap_datadev_bnobt_helper, info);
> +}
> +
> +/* Execute a getfsmap query against the regular data device's bnobt. */
> +STATIC int
> +xfs_getfsmap_datadev_bnobt(
> +	struct xfs_trans		*tp,
> +	struct xfs_fsmap		*keys,
> +	struct xfs_getfsmap_info	*info)
> +{
> +	struct xfs_alloc_rec_incore	akeys[2];
> +
> +	info->missing_owner = XFS_FMR_OWN_UNKNOWN;
> +	return __xfs_getfsmap_datadev(tp, keys, info,
> +			xfs_getfsmap_datadev_bnobt_query, &akeys[0]);
> +}
> +
>  /* Do we recognize the device? */
>  STATIC bool
>  xfs_getfsmap_is_valid_device(
> @@ -668,8 +733,6 @@ xfs_getfsmap(
>  	int				i;
>  	int				error = 0;
>  
> -	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> -		return -EOPNOTSUPP;
>  	if (head->fmh_iflags & ~FMH_IF_VALID)
>  		return -EINVAL;
>  	if (!xfs_getfsmap_is_valid_device(mp, &head->fmh_keys[0]) ||
> @@ -681,7 +744,10 @@ xfs_getfsmap(
>  	/* Set up our device handlers. */
>  	memset(handlers, 0, sizeof(handlers));
>  	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
> -	handlers[0].fn = xfs_getfsmap_datadev_rmapbt;
> +	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> +		handlers[0].fn = xfs_getfsmap_datadev_rmapbt;
> +	else
> +		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
>  	if (mp->m_logdev_targp != mp->m_ddev_targp) {
>  		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
>  		handlers[1].fn = xfs_getfsmap_logdev;
> --
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