Re: [PATCH 3/9] xfs_repair: create a new class of btree rebuild cursors

[Brian Foster <bfoster@redhat.com>]

On Sat, May 09, 2020 at 09:31:59AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Create some new support structures and functions to assist phase5 in
> using the btree bulk loader to reconstruct metadata btrees.  This is the
> first step in removing the open-coded rebuilding code.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

FYI, unused variable warnings:

phase5.c: In function ‘phase5_func’:
phase5.c:2491:20: warning: unused variable ‘sc’ [-Wunused-variable]
 2491 |  struct repair_ctx sc = { .mp = mp, };
      |                    ^~
At top level:
phase5.c:509:1: warning: ‘finish_rebuild’ defined but not used [-Wunused-function]
  509 | finish_rebuild(
      | ^~~~~~~~~~~~~~
phase5.c:468:1: warning: ‘rebuild_alloc_block’ defined but not used [-Wunused-function]
  468 | rebuild_alloc_block(
      | ^~~~~~~~~~~~~~~~~~~
phase5.c:381:1: warning: ‘setup_rebuild’ defined but not used [-Wunused-function]
  381 | setup_rebuild(
      | ^~~~~~~~~~~~~
phase5.c:366:1: warning: ‘init_rebuild’ defined but not used [-Wunused-function]
  366 | init_rebuild(
      | ^~~~~~~~~~~~

>  repair/phase5.c |  240 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 219 insertions(+), 21 deletions(-)
> 
> 
> diff --git a/repair/phase5.c b/repair/phase5.c
> index f3be15de..7eb24519 100644
> --- a/repair/phase5.c
> +++ b/repair/phase5.c
...
> @@ -306,6 +324,157 @@ _("error - not enough free space in filesystem\n"));
...
> +/* Reserve blocks for the new btree. */
> +static void
> +setup_rebuild(
> +	struct xfs_mount	*mp,
> +	xfs_agnumber_t		agno,
> +	struct bt_rebuild	*btr,
> +	uint32_t		nr_blocks)
> +{
> +	struct extent_tree_node	*ext_ptr;
> +	struct extent_tree_node	*bno_ext_ptr;
> +	uint32_t		blocks_allocated = 0;
> +	int			error;
> +
> +	/*
> +	 * grab the smallest extent and use it up, then get the
> +	 * next smallest.  This mimics the init_*_cursor code.
> +	 */
> +	ext_ptr =  findfirst_bcnt_extent(agno);
> +
> +	/*
> +	 * set up the free block array
> +	 */
> +	while (blocks_allocated < nr_blocks)  {
> +		uint64_t	len;
> +		xfs_agblock_t	new_start;
> +		xfs_extlen_t	new_len;
> +
> +		if (!ext_ptr)
> +			do_error(
> +_("error - not enough free space in filesystem\n"));
> +
> +		/* Use up the extent we've got. */
> +		len = min(ext_ptr->ex_blockcount,
> +				btr->bload.nr_blocks - blocks_allocated);

What's the difference between the nr_blocks parameter and this one?

> +		error = xrep_newbt_add_reservation(&btr->newbt,
> +				XFS_AGB_TO_FSB(mp, agno,
> +					       ext_ptr->ex_startblock),
> +				len, NULL);
> +		if (error)
> +			do_error(_("could not set up btree reservation: %s\n"),
> +				strerror(-error));
> +		blocks_allocated += len;
> +
> +		error = rmap_add_ag_rec(mp, agno, ext_ptr->ex_startblock, len,
> +				btr->newbt.oinfo.oi_owner);
> +		if (error)
> +			do_error(_("could not set up btree rmaps: %s\n"),
> +				strerror(-error));
> +
> +		/* Figure out if we're putting anything back. */

The remaining extent replacement bits of this loop looks like it could
warrant a little helper and a comment to explain exactly what's
happening at a high level.

Brian

> +		new_start = ext_ptr->ex_startblock + len;
> +		new_len = ext_ptr->ex_blockcount - len;
> +
> +		/* Delete the used-up extent from both extent trees. */
> +#ifdef XR_BLD_FREE_TRACE
> +		fprintf(stderr, "releasing extent: %u [%u %u]\n",
> +			agno, ext_ptr->ex_startblock, ext_ptr->ex_blockcount);
> +#endif
> +		bno_ext_ptr = find_bno_extent(agno, ext_ptr->ex_startblock);
> +		ASSERT(bno_ext_ptr != NULL);
> +		get_bno_extent(agno, bno_ext_ptr);
> +		release_extent_tree_node(bno_ext_ptr);
> +
> +		ext_ptr = get_bcnt_extent(agno, ext_ptr->ex_startblock,
> +				ext_ptr->ex_blockcount);
> +		ASSERT(ext_ptr != NULL);
> +		release_extent_tree_node(ext_ptr);
> +
> +		/*
> +		 * If we only used part of this last extent, then we need only
> +		 * to reinsert the extent in the extent trees and we're done.
> +		 */
> +		if (new_len > 0) {
> +			add_bno_extent(agno, new_start, new_len);
> +			add_bcnt_extent(agno, new_start, new_len);
> +			break;
> +		}
> +
> +		/* Otherwise, find the next biggest extent. */
> +		ext_ptr = findfirst_bcnt_extent(agno);
> +	}
> +#ifdef XR_BLD_FREE_TRACE
> +	fprintf(stderr, "blocks_allocated = %d\n",
> +		blocks_allocated);
> +#endif
> +}
> +
> +/* Feed one of the new btree blocks to the bulk loader. */
> +static int
> +rebuild_alloc_block(
> +	struct xfs_btree_cur	*cur,
> +	union xfs_btree_ptr	*ptr,
> +	void			*priv)
> +{
> +	struct bt_rebuild	*btr = priv;
> +
> +	return xrep_newbt_claim_block(cur, &btr->newbt, ptr);
> +}
> +
>  static void
>  write_cursor(bt_status_t *curs)
>  {
> @@ -336,6 +505,34 @@ finish_cursor(bt_status_t *curs)
>  	free(curs->btree_blocks);
>  }
>  
> +static void
> +finish_rebuild(
> +	struct xfs_mount	*mp,
> +	struct bt_rebuild	*btr)
> +{
> +	struct xrep_newbt_resv	*resv, *n;
> +
> +	for_each_xrep_newbt_reservation(&btr->newbt, resv, n) {
> +		xfs_agnumber_t	agno;
> +		xfs_agblock_t	bno;
> +		xfs_extlen_t	len;
> +
> +		if (resv->used >= resv->len)
> +			continue;
> +
> +		/* XXX: Shouldn't this go on the AGFL? */
> +		/* Put back everything we didn't use. */
> +		bno = XFS_FSB_TO_AGBNO(mp, resv->fsbno + resv->used);
> +		agno = XFS_FSB_TO_AGNO(mp, resv->fsbno + resv->used);
> +		len = resv->len - resv->used;
> +
> +		add_bno_extent(agno, bno, len);
> +		add_bcnt_extent(agno, bno, len);
> +	}
> +
> +	xrep_newbt_destroy(&btr->newbt, 0);
> +}
> +
>  /*
>   * We need to leave some free records in the tree for the corner case of
>   * setting up the AGFL. This may require allocation of blocks, and as
> @@ -2290,28 +2487,29 @@ keep_fsinos(xfs_mount_t *mp)
>  
>  static void
>  phase5_func(
> -	xfs_mount_t	*mp,
> -	xfs_agnumber_t	agno,
> -	struct xfs_slab	*lost_fsb)
> +	struct xfs_mount	*mp,
> +	xfs_agnumber_t		agno,
> +	struct xfs_slab		*lost_fsb)
>  {
> -	uint64_t	num_inos;
> -	uint64_t	num_free_inos;
> -	uint64_t	finobt_num_inos;
> -	uint64_t	finobt_num_free_inos;
> -	bt_status_t	bno_btree_curs;
> -	bt_status_t	bcnt_btree_curs;
> -	bt_status_t	ino_btree_curs;
> -	bt_status_t	fino_btree_curs;
> -	bt_status_t	rmap_btree_curs;
> -	bt_status_t	refcnt_btree_curs;
> -	int		extra_blocks = 0;
> -	uint		num_freeblocks;
> -	xfs_extlen_t	freeblks1;
> +	struct repair_ctx	sc = { .mp = mp, };
> +	struct agi_stat		agi_stat = {0,};
> +	uint64_t		num_inos;
> +	uint64_t		num_free_inos;
> +	uint64_t		finobt_num_inos;
> +	uint64_t		finobt_num_free_inos;
> +	bt_status_t		bno_btree_curs;
> +	bt_status_t		bcnt_btree_curs;
> +	bt_status_t		ino_btree_curs;
> +	bt_status_t		fino_btree_curs;
> +	bt_status_t		rmap_btree_curs;
> +	bt_status_t		refcnt_btree_curs;
> +	int			extra_blocks = 0;
> +	uint			num_freeblocks;
> +	xfs_extlen_t		freeblks1;
>  #ifdef DEBUG
> -	xfs_extlen_t	freeblks2;
> +	xfs_extlen_t		freeblks2;
>  #endif
> -	xfs_agblock_t	num_extents;
> -	struct agi_stat	agi_stat = {0,};
> +	xfs_agblock_t		num_extents;
>  
>  	if (verbose)
>  		do_log(_("        - agno = %d\n"), agno);
> @@ -2533,8 +2731,8 @@ inject_lost_blocks(
>  		if (error)
>  			goto out_cancel;
>  
> -		error = -libxfs_free_extent(tp, *fsb, 1, &XFS_RMAP_OINFO_AG,
> -					    XFS_AG_RESV_NONE);
> +		error = -libxfs_free_extent(tp, *fsb, 1,
> +				&XFS_RMAP_OINFO_ANY_OWNER, XFS_AG_RESV_NONE);
>  		if (error)
>  			goto out_cancel;
>  
>