Re: [PATCH 04/14] xfs: repair inode btrees

Dave Chinner
2018-06-04T03:41:32Z

On Wed, May 30, 2018 at 12:31:04PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Use the rmapbt to find inode chunks, query the chunks to compute
> hole and free masks, and with that information rebuild the inobt
> and finobt.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

[...]

> +xfs_repair_ialloc_check_free(
> + struct xfs_btree_cur *cur,
> + struct xfs_buf *bp,
> + xfs_ino_t fsino,
> + xfs_agino_t bpino,
> + bool *inuse)
> +{
> + struct xfs_mount *mp = cur->bc_mp;
> + struct xfs_dinode *dip;
> + int error;
> +
> + /* Will the in-core inode tell us if it's in use? */
> + error = xfs_icache_inode_is_allocated(mp, cur->bc_tp, fsino, inuse);
> + if (!error)
> + return 0;
> +
> + /* Inode uncached or half assembled, read disk buffer */
> + dip = xfs_buf_offset(bp, bpino * mp->m_sb.sb_inodesize);
> + if (be16_to_cpu(dip->di_magic) != XFS_DINODE_MAGIC)
> + return -EFSCORRUPTED;

Do we hold the buffer locked here? i.e. can we race with someone
else allocating/freeing/reading the inode?

> +
> + if (dip->di_version >= 3 && be64_to_cpu(dip->di_ino) != fsino)
> + return -EFSCORRUPTED;
> +
> + *inuse = dip->di_mode != 0;
> + return 0;
> +}
> +
> +/* Record extents that belong to inode btrees. */
> +STATIC int
> +xfs_repair_ialloc_extent_fn(
> + struct xfs_btree_cur *cur,
> + struct xfs_rmap_irec *rec,
> + void *priv)
> +{
> + struct xfs_imap imap;
> + struct xfs_repair_ialloc *ri = priv;
> + struct xfs_repair_ialloc_extent *rie;
> + struct xfs_dinode *dip;
> + struct xfs_buf *bp;
> + struct xfs_mount *mp = cur->bc_mp;
> + xfs_ino_t fsino;
> + xfs_inofree_t usedmask;
> + xfs_fsblock_t fsbno;
> + xfs_agnumber_t agno;
> + xfs_agblock_t agbno;
> + xfs_agino_t cdist;
> + xfs_agino_t startino;
> + xfs_agino_t clusterino;
> + xfs_agino_t nr_inodes;
> + xfs_agino_t inoalign;
> + xfs_agino_t agino;
> + xfs_agino_t rmino;
> + uint16_t fillmask;
> + bool inuse;
> + int blks_per_cluster;
> + int usedcount;
> + int error = 0;
> +
> + if (xfs_scrub_should_terminate(ri->sc, &error))
> + return error;
> +
> + /* Fragment of the old btrees; dispose of them later. */
> + if (rec->rm_owner == XFS_RMAP_OWN_INOBT) {
> + fsbno = XFS_AGB_TO_FSB(cur->bc_mp, cur->bc_private.a.agno,
> + rec->rm_startblock);
> + return xfs_repair_collect_btree_extent(ri->sc, &ri->btlist,
> + fsbno, rec->rm_blockcount);
> + }
> +
> + /* Skip extents which are not owned by this inode and fork. */
> + if (rec->rm_owner != XFS_RMAP_OWN_INODES)
> + return 0;
> +
> + agno = cur->bc_private.a.agno;
> + blks_per_cluster = xfs_icluster_size_fsb(mp);
> + nr_inodes = XFS_OFFBNO_TO_AGINO(mp, blks_per_cluster, 0);
> +
> + if (rec->rm_startblock % blks_per_cluster != 0)
> + return -EFSCORRUPTED;
> +
> + trace_xfs_repair_ialloc_extent_fn(mp, cur->bc_private.a.agno,
> + rec->rm_startblock, rec->rm_blockcount, rec->rm_owner,
> + rec->rm_offset, rec->rm_flags);
> +
> + /*
> + * Determine the inode block alignment, and where the block
> + * ought to start if it's aligned properly. On a sparse inode
> + * system the rmap doesn't have to start on an alignment boundary,
> + * but the record does. On pre-sparse filesystems, we /must/
> + * start both rmap and inobt on an alignment boundary.
> + */
> + inoalign = xfs_ialloc_cluster_alignment(mp);
> + agbno = rec->rm_startblock;
> + agino = XFS_OFFBNO_TO_AGINO(mp, agbno, 0);
> + rmino = XFS_OFFBNO_TO_AGINO(mp, rounddown(agbno, inoalign), 0);
> + if (!xfs_sb_version_hassparseinodes(&mp->m_sb) && agino != rmino)
> + return -EFSCORRUPTED;
> +
> + /*
> + * For each cluster in this blob of inode, we must calculate the
> + * properly aligned startino of that cluster, then iterate each
> + * cluster to fill in used and filled masks appropriately. We
> + * then use the (startino, used, filled) information to construct
> + * the appropriate inode records.
> + */
> + for (agbno = rec->rm_startblock;
> + agbno < rec->rm_startblock + rec->rm_blockcount;
> + agbno += blks_per_cluster) {

I see a few problems with indenting and "just over" long lines here.
Can you factor the loop internals into a separate function to reduce
that issue? Say xfs_repair_ialloc_process_cluster()?

> + /* The per-AG inum of this inode cluster. */
> + agino = XFS_OFFBNO_TO_AGINO(mp, agbno, 0);
> +
> + /* The per-AG inum of the inobt record. */
> + startino = rmino +
> + rounddown(agino - rmino, XFS_INODES_PER_CHUNK);
> + cdist = agino - startino;

What's "cdist" mean? I can guess at it's meaning, but I don't recall
seeing the inode number offset into a cluster been refered to as a
distanced before....

> + /* Every inode in this holemask slot is filled. */
> + fillmask = xfs_inobt_maskn(
> + cdist / XFS_INODES_PER_HOLEMASK_BIT,
> + nr_inodes / XFS_INODES_PER_HOLEMASK_BIT);
> +
> + /* Grab the inode cluster buffer. */
> + imap.im_blkno = XFS_AGB_TO_DADDR(mp, agno, agbno);
> + imap.im_len = XFS_FSB_TO_BB(mp, blks_per_cluster);
> + imap.im_boffset = 0;
> +
> + error = xfs_imap_to_bp(mp, cur->bc_tp, &imap,
> + &dip, &bp, 0, XFS_IGET_UNTRUSTED);
> + if (error)
> + return error;
> +
> + usedmask = 0;
> + usedcount = 0;
> + /* Which inodes within this cluster are free? */
> + for (clusterino = 0; clusterino < nr_inodes; clusterino++) {
> + fsino = XFS_AGINO_TO_INO(mp, cur->bc_private.a.agno,
> + agino + clusterino);
> + error = xfs_repair_ialloc_check_free(cur, bp, fsino,
> + clusterino, &inuse);
> + if (error) {
> + xfs_trans_brelse(cur->bc_tp, bp);
> + return error;
> + }
> + if (inuse) {
> + usedcount++;
> + usedmask |= XFS_INOBT_MASK(cdist + clusterino);
> + }
> + }
> + xfs_trans_brelse(cur->bc_tp, bp);
> +
> + /*
> + * If the last item in the list is our chunk record,
> + * update that.
> + */
> + if (!list_empty(&ri->extlist)) {
> + rie = list_last_entry(&ri->extlist,
> + struct xfs_repair_ialloc_extent, list);
> + if (rie->startino + XFS_INODES_PER_CHUNK > startino) {
> + rie->freemask &= ~usedmask;
> + rie->holemask &= ~fillmask;
> + rie->count += nr_inodes;
> + rie->usedcount += usedcount;
> + continue;
> + }
> + }
> +
> + /* New inode chunk; add to the list. */
> + rie = kmem_alloc(sizeof(struct xfs_repair_ialloc_extent),
> + KM_MAYFAIL);
> + if (!rie)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&rie->list);
> + rie->startino = startino;
> + rie->freemask = XFS_INOBT_ALL_FREE & ~usedmask;
> + rie->holemask = XFS_INOBT_ALL_FREE & ~fillmask;
> + rie->count = nr_inodes;
> + rie->usedcount = usedcount;
> + list_add_tail(&rie->list, &ri->extlist);
> + ri->nr_records++;
> + }
> +
> + return 0;
> +}

[....]

> +/* Repair both inode btrees. */
> +int
> +xfs_repair_iallocbt(
> + struct xfs_scrub_context *sc)
> +{
> + struct xfs_repair_ialloc ri;
> + struct xfs_owner_info oinfo;
> + struct xfs_mount *mp = sc->mp;
> + struct xfs_buf *bp;
> + struct xfs_repair_ialloc_extent *rie;
> + struct xfs_repair_ialloc_extent *n;
> + struct xfs_agi *agi;
> + struct xfs_btree_cur *cur = NULL;
> + struct xfs_perag *pag;
> + xfs_fsblock_t inofsb;
> + xfs_fsblock_t finofsb;
> + xfs_extlen_t nr_blocks;
> + xfs_agino_t old_count;
> + xfs_agino_t old_freecount;
> + xfs_agino_t freecount;
> + unsigned int count;
> + unsigned int usedcount;
> + int logflags;
> + int error = 0;
> +
> + /* We require the rmapbt to rebuild anything. */
> + if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
> + return -EOPNOTSUPP;

This could be factored similarly to the allocbt repair function.

> +
> + xfs_scrub_perag_get(sc->mp, &sc->sa);
> + pag = sc->sa.pag;
> + /* Collect all reverse mappings for inode blocks. */
> + xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_INOBT);
> + INIT_LIST_HEAD(&ri.extlist);
> + xfs_repair_init_extent_list(&ri.btlist);
> + ri.nr_records = 0;
> + ri.sc = sc;
> +
> + cur = xfs_rmapbt_init_cursor(mp, sc->tp, sc->sa.agf_bp, sc->sa.agno);
> + error = xfs_rmap_query_all(cur, xfs_repair_ialloc_extent_fn, &ri);
> + if (error)
> + goto out;
> + xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
> + cur = NULL;
> +
> + /* Do we actually have enough space to do this? */
> + nr_blocks = xfs_iallocbt_calc_size(mp, ri.nr_records);
> + if (xfs_sb_version_hasfinobt(&mp->m_sb))
> + nr_blocks *= 2;
> + if (!xfs_repair_ag_has_space(pag, nr_blocks, XFS_AG_RESV_NONE)) {
> + error = -ENOSPC;
> + goto out;
> + }
> +
> + /* Invalidate all the inobt/finobt blocks in btlist. */
> + error = xfs_repair_invalidate_blocks(sc, &ri.btlist);
> + if (error)
> + goto out;
> +
> + agi = XFS_BUF_TO_AGI(sc->sa.agi_bp);
> + /* Initialize new btree roots. */
> + error = xfs_repair_alloc_ag_block(sc, &oinfo, &inofsb,
> + XFS_AG_RESV_NONE);
> + if (error)
> + goto out;
> + error = xfs_repair_init_btblock(sc, inofsb, &bp, XFS_BTNUM_INO,
> + &xfs_inobt_buf_ops);
> + if (error)
> + goto out;
> + agi->agi_root = cpu_to_be32(XFS_FSB_TO_AGBNO(mp, inofsb));
> + agi->agi_level = cpu_to_be32(1);
> + logflags = XFS_AGI_ROOT | XFS_AGI_LEVEL;
> +
> + if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
> + error = xfs_repair_alloc_ag_block(sc, &oinfo, &finofsb,
> + mp->m_inotbt_nores ? XFS_AG_RESV_NONE :
> + XFS_AG_RESV_METADATA);
> + if (error)
> + goto out;
> + error = xfs_repair_init_btblock(sc, finofsb, &bp,
> + XFS_BTNUM_FINO, &xfs_inobt_buf_ops);
> + if (error)
> + goto out;
> + agi->agi_free_root = cpu_to_be32(XFS_FSB_TO_AGBNO(mp, finofsb));
> + agi->agi_free_level = cpu_to_be32(1);
> + logflags |= XFS_AGI_FREE_ROOT | XFS_AGI_FREE_LEVEL;
> + }
> +
> + xfs_ialloc_log_agi(sc->tp, sc->sa.agi_bp, logflags);
> + error = xfs_repair_roll_ag_trans(sc);
> + if (error)
> + goto out;
> +
> + /* Insert records into the new btrees. */
> + count = 0;
> + usedcount = 0;
> + list_sort(NULL, &ri.extlist, xfs_repair_ialloc_extent_cmp);
> + list_for_each_entry_safe(rie, n, &ri.extlist, list) {
> + count += rie->count;
> + usedcount += rie->usedcount;
> +
> + error = xfs_repair_iallocbt_insert_rec(sc, rie);
> + if (error)
> + goto out;
> +
> + list_del(&rie->list);
> + kmem_free(rie);
> + }
> +
> +
> + /* Update the AGI counters. */
> + agi = XFS_BUF_TO_AGI(sc->sa.agi_bp);
> + old_count = be32_to_cpu(agi->agi_count);
> + old_freecount = be32_to_cpu(agi->agi_freecount);
> + freecount = count - usedcount;
> +
> + xfs_repair_mod_ino_counts(sc, old_count, count, old_freecount,
> + freecount);
> +
> + if (count != old_count) {
> + if (sc->sa.pag->pagi_init)
> + sc->sa.pag->pagi_count = count;
> + agi->agi_count = cpu_to_be32(count);
> + xfs_ialloc_log_agi(sc->tp, sc->sa.agi_bp, XFS_AGI_COUNT);
> + }
> +
> + if (freecount != old_freecount) {
> + if (sc->sa.pag->pagi_init)
> + sc->sa.pag->pagi_freecount = freecount;

We've read the AGI buffer in at this point, right? so it is
guaranteed that pagi_init is true, right?

> + agi->agi_freecount = cpu_to_be32(freecount);
> + xfs_ialloc_log_agi(sc->tp, sc->sa.agi_bp, XFS_AGI_FREECOUNT);
> + }
> +
> + /* Free the old inode btree blocks if they're not in use. */
> + return xfs_repair_reap_btree_extents(sc, &ri.btlist, &oinfo,
> + XFS_AG_RESV_NONE);
> +out:

out_error, perhaps, to distinguish it from the normal function
return path? (and perhaps apply that to all the previous main reapir
functions on factoring?)

> + if (cur)
> + xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
> + xfs_repair_cancel_btree_extents(sc, &ri.btlist);
> + list_for_each_entry_safe(rie, n, &ri.extlist, list) {
> + list_del(&rie->list);
> + kmem_free(rie);
> + }
> + return error;
> +}

-Dave.

--
Dave Chinner
david@fromorbit.com