Re: [PATCH 3/4] xfs: repair the AGFL

[Brian Foster <bfoster@redhat.com>]

On Tue, Aug 07, 2018 at 08:57:19PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Repair the AGFL from the rmap data.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/scrub/agheader_repair.c |  284 ++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/scrub/bitmap.c          |   92 +++++++++++++
>  fs/xfs/scrub/bitmap.h          |    4 +
>  fs/xfs/scrub/repair.h          |    2 
>  fs/xfs/scrub/scrub.c           |    2 
>  5 files changed, 383 insertions(+), 1 deletion(-)
> 
> 
> diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> index 4842fc598c9b..0decf711b3c7 100644
> --- a/fs/xfs/scrub/agheader_repair.c
> +++ b/fs/xfs/scrub/agheader_repair.c
> @@ -424,3 +424,287 @@ xrep_agf(
...
> +/* Repair the AGFL. */
> +int
> +xrep_agfl(
> +	struct xfs_scrub	*sc)
> +{
> +	struct xfs_owner_info	oinfo;
> +	struct xfs_bitmap	agfl_extents;
> +	struct xfs_mount	*mp = sc->mp;
> +	struct xfs_buf		*agf_bp;
> +	struct xfs_buf		*agfl_bp;
> +	xfs_agblock_t		flcount;
> +	int			error;
> +
> +	/* We require the rmapbt to rebuild anything. */
> +	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> +		return -EOPNOTSUPP;
> +
> +	xchk_perag_get(sc->mp, &sc->sa);
> +	xfs_bitmap_init(&agfl_extents);
> +
> +	/*
> +	 * Read the AGF so that we can query the rmapbt.  We hope that there's
> +	 * nothing wrong with the AGF, but all the AG header repair functions
> +	 * have this chicken-and-egg problem.
> +	 */
> +	error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.agno, 0, &agf_bp);
> +	if (error)
> +		return error;
> +	if (!agf_bp)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Make sure we have the AGFL buffer, as scrub might have decided it
> +	 * was corrupt after xfs_alloc_read_agfl failed with -EFSCORRUPTED.
> +	 */
> +	error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
> +			XFS_AG_DADDR(mp, sc->sa.agno, XFS_AGFL_DADDR(mp)),
> +			XFS_FSS_TO_BB(mp, 1), 0, &agfl_bp, NULL);
> +	if (error)
> +		return error;
> +	agfl_bp->b_ops = &xfs_agfl_buf_ops;
> +
> +	/* Gather all the extents we're going to put on the new AGFL. */
> +	error = xrep_agfl_collect_blocks(sc, agf_bp, &agfl_extents, &flcount);
> +	if (error)
> +		goto err;
> +
> +	/*
> +	 * Update AGF and AGFL.  We reset the global free block counter when
> +	 * we adjust the AGF flcount (which can fail) so avoid updating any
> +	 * buffers until we know that part works.
> +	 */
> +	error = xrep_agfl_update_agf(sc, agf_bp, flcount);
> +	if (error)
> +		goto err;
> +	xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount);
> +
> +	/*
> +	 * Ok, the AGFL should be ready to go now.  Roll the transaction to
> +	 * make the new AGFL permanent before we start using it to return
> +	 * freespace overflow to the freespace btrees.
> +	 */
> +	sc->sa.agf_bp = agf_bp;
> +	sc->sa.agfl_bp = agfl_bp;
> +	error = xrep_roll_ag_trans(sc);
> +	if (error)
> +		goto err;
> +
> +	/* Dump any AGFL overflow. */
> +	xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_AG);
> +	return xrep_reap_extents(sc, &agfl_extents, &oinfo, XFS_AG_RESV_AGFL);
> +err:
> +	xfs_bitmap_destroy(&agfl_extents);
> +	return error;

Was there a reason we don't maintain the ability to revert the AGFL on
error as is done in the AGF repair case? I take it we'll end up shutting
down the fs if anything causes us to fail once we've logged the
associated agf fields in xrep_agfl_update_agf()..?

Brian

> +}
> diff --git a/fs/xfs/scrub/bitmap.c b/fs/xfs/scrub/bitmap.c
> index c770e2d0b6aa..fdadc9e1dc49 100644
> --- a/fs/xfs/scrub/bitmap.c
> +++ b/fs/xfs/scrub/bitmap.c
> @@ -9,6 +9,7 @@
>  #include "xfs_format.h"
>  #include "xfs_trans_resv.h"
>  #include "xfs_mount.h"
> +#include "xfs_btree.h"
>  #include "scrub/xfs_scrub.h"
>  #include "scrub/scrub.h"
>  #include "scrub/common.h"
> @@ -209,3 +210,94 @@ xfs_bitmap_disunion(
>  }
>  #undef LEFT_ALIGNED
>  #undef RIGHT_ALIGNED
> +
> +/*
> + * Record all btree blocks seen while iterating all records of a btree.
> + *
> + * We know that the btree query_all function starts at the left edge and walks
> + * towards the right edge of the tree.  Therefore, we know that we can walk up
> + * the btree cursor towards the root; if the pointer for a given level points
> + * to the first record/key in that block, we haven't seen this block before;
> + * and therefore we need to remember that we saw this block in the btree.
> + *
> + * So if our btree is:
> + *
> + *    4
> + *  / | \
> + * 1  2  3
> + *
> + * Pretend for this example that each leaf block has 100 btree records.  For
> + * the first btree record, we'll observe that bc_ptrs[0] == 1, so we record
> + * that we saw block 1.  Then we observe that bc_ptrs[1] == 1, so we record
> + * block 4.  The list is [1, 4].
> + *
> + * For the second btree record, we see that bc_ptrs[0] == 2, so we exit the
> + * loop.  The list remains [1, 4].
> + *
> + * For the 101st btree record, we've moved onto leaf block 2.  Now
> + * bc_ptrs[0] == 1 again, so we record that we saw block 2.  We see that
> + * bc_ptrs[1] == 2, so we exit the loop.  The list is now [1, 4, 2].
> + *
> + * For the 102nd record, bc_ptrs[0] == 2, so we continue.
> + *
> + * For the 201st record, we've moved on to leaf block 3.  bc_ptrs[0] == 1, so
> + * we add 3 to the list.  Now it is [1, 4, 2, 3].
> + *
> + * For the 300th record we just exit, with the list being [1, 4, 2, 3].
> + */
> +
> +/*
> + * Record all the buffers pointed to by the btree cursor.  Callers already
> + * engaged in a btree walk should call this function to capture the list of
> + * blocks going from the leaf towards the root.
> + */
> +int
> +xfs_bitmap_set_btcur_path(
> +	struct xfs_bitmap	*bitmap,
> +	struct xfs_btree_cur	*cur)
> +{
> +	struct xfs_buf		*bp;
> +	xfs_fsblock_t		fsb;
> +	int			i;
> +	int			error;
> +
> +	for (i = 0; i < cur->bc_nlevels && cur->bc_ptrs[i] == 1; i++) {
> +		xfs_btree_get_block(cur, i, &bp);
> +		if (!bp)
> +			continue;
> +		fsb = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
> +		error = xfs_bitmap_set(bitmap, fsb, 1);
> +		if (error)
> +			return error;
> +	}
> +
> +	return 0;
> +}
> +
> +/* Collect a btree's block in the bitmap. */
> +STATIC int
> +xfs_bitmap_collect_btblock(
> +	struct xfs_btree_cur	*cur,
> +	int			level,
> +	void			*priv)
> +{
> +	struct xfs_bitmap	*bitmap = priv;
> +	struct xfs_buf		*bp;
> +	xfs_fsblock_t		fsbno;
> +
> +	xfs_btree_get_block(cur, level, &bp);
> +	if (!bp)
> +		return 0;
> +
> +	fsbno = XFS_DADDR_TO_FSB(cur->bc_mp, bp->b_bn);
> +	return xfs_bitmap_set(bitmap, fsbno, 1);
> +}
> +
> +/* Walk the btree and mark the bitmap wherever a btree block is found. */
> +int
> +xfs_bitmap_set_btblocks(
> +	struct xfs_bitmap	*bitmap,
> +	struct xfs_btree_cur	*cur)
> +{
> +	return xfs_btree_visit_blocks(cur, xfs_bitmap_collect_btblock, bitmap);
> +}
> diff --git a/fs/xfs/scrub/bitmap.h b/fs/xfs/scrub/bitmap.h
> index dad652ee9177..ae8ecbce6fa6 100644
> --- a/fs/xfs/scrub/bitmap.h
> +++ b/fs/xfs/scrub/bitmap.h
> @@ -28,5 +28,9 @@ void xfs_bitmap_destroy(struct xfs_bitmap *bitmap);
>  
>  int xfs_bitmap_set(struct xfs_bitmap *bitmap, uint64_t start, uint64_t len);
>  int xfs_bitmap_disunion(struct xfs_bitmap *bitmap, struct xfs_bitmap *sub);
> +int xfs_bitmap_set_btcur_path(struct xfs_bitmap *bitmap,
> +		struct xfs_btree_cur *cur);
> +int xfs_bitmap_set_btblocks(struct xfs_bitmap *bitmap,
> +		struct xfs_btree_cur *cur);
>  
>  #endif	/* __XFS_SCRUB_BITMAP_H__ */
> diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h
> index 6f0903c51a47..1d283360b5ab 100644
> --- a/fs/xfs/scrub/repair.h
> +++ b/fs/xfs/scrub/repair.h
> @@ -59,6 +59,7 @@ int xrep_ino_dqattach(struct xfs_scrub *sc);
>  int xrep_probe(struct xfs_scrub *sc);
>  int xrep_superblock(struct xfs_scrub *sc);
>  int xrep_agf(struct xfs_scrub *sc);
> +int xrep_agfl(struct xfs_scrub *sc);
>  
>  #else
>  
> @@ -83,6 +84,7 @@ xrep_calc_ag_resblks(
>  #define xrep_probe			xrep_notsupported
>  #define xrep_superblock			xrep_notsupported
>  #define xrep_agf			xrep_notsupported
> +#define xrep_agfl			xrep_notsupported
>  
>  #endif /* CONFIG_XFS_ONLINE_REPAIR */
>  
> diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
> index 1e8a17c8e2b9..2670f4cf62f4 100644
> --- a/fs/xfs/scrub/scrub.c
> +++ b/fs/xfs/scrub/scrub.c
> @@ -220,7 +220,7 @@ static const struct xchk_meta_ops meta_scrub_ops[] = {
>  		.type	= ST_PERAG,
>  		.setup	= xchk_setup_fs,
>  		.scrub	= xchk_agfl,
> -		.repair	= xrep_notsupported,
> +		.repair	= xrep_agfl,
>  	},
>  	[XFS_SCRUB_TYPE_AGI] = {	/* agi */
>  		.type	= ST_PERAG,
> 
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