On Mon, Jul 30, 2018 at 02:20:51PM -0400, Brian Foster wrote:
> On Sun, Jul 29, 2018 at 10:48:15PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Rebuild the AGI header items with some help from the rmapbt.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
>
> A couple nits and future thoughts..
>
> > fs/xfs/scrub/agheader_repair.c | 220 ++++++++++++++++++++++++++++++++++++++++
> > fs/xfs/scrub/repair.h | 2
> > fs/xfs/scrub/scrub.c | 2
> > 3 files changed, 223 insertions(+), 1 deletion(-)
> >
> >
> > diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> > index bfef066c87c3..921e7d42a2ef 100644
> > --- a/fs/xfs/scrub/agheader_repair.c
> > +++ b/fs/xfs/scrub/agheader_repair.c
> > @@ -700,3 +700,223 @@ xrep_agfl(
> > xfs_bitmap_destroy(&agfl_extents);
> > return error;
> > }
> ...
> > +STATIC int
> > +xrep_agi_find_btrees(
> > + struct xfs_scrub *sc,
> > + struct xrep_find_ag_btree *fab)
> > +{
> > + struct xfs_buf *agf_bp;
> > + struct xfs_mount *mp = sc->mp;
> > + int error;
> > +
> > + /* Read the AGF. */
> > + error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.agno, 0, &agf_bp);
> > + if (error)
> > + return error;
> > + if (!agf_bp)
> > + return -ENOMEM;
> > +
> > + /* Find the btree roots. */
> > + error = xrep_find_ag_btree_roots(sc, agf_bp, fab, NULL);
> > + if (error)
> > + return error;
> > +
> > + /* We must find the inobt root. */
> > + if (fab[XREP_AGI_INOBT].root == NULLAGBLOCK ||
> > + fab[XREP_AGI_INOBT].height > XFS_BTREE_MAXLEVELS)
> > + return -EFSCORRUPTED;
> > +
> > + /* We must find the finobt root if that feature is enabled. */
> > + if (xfs_sb_version_hasfinobt(&mp->m_sb) &&
> > + (fab[XREP_AGI_FINOBT].root == NULLAGBLOCK ||
> > + fab[XREP_AGI_FINOBT].height > XFS_BTREE_MAXLEVELS))
> > + return -EFSCORRUPTED;
>
> Skimming around some of the existing code to find the btree roots, I
> notice that the .root field is going to be != NULLAGBLOCK so long as we
> find at least one appropriately typed block in the rmapbt. I know you
> mentioned that we depend on a correct rmapbt atm, but I'm wondering if
> there's room for slightly more robust error checks to at least prevent
> us from doing something damaging. For example, perhaps we could unset
> .root when we've found a second block at the same level as the current
> "root," and/or check some of the generic characteristics of a root btree
> block (no left/right siblings) once we're done..?
Good suggestion, I'll add it to xrep_findroot_block.
> > +
> > + return 0;
> > +}
> > +
> ...
> > +/* Trigger reinitialization of the in-core data. */
> > +STATIC int
> > +xrep_agi_commit_new(
> > + struct xfs_scrub *sc,
> > + struct xfs_buf *agi_bp,
> > + const struct xfs_agi *old_agi)
>
> old_agi is unused here.
>
> > +{
> > + struct xfs_perag *pag;
> > + struct xfs_agi *agi = XFS_BUF_TO_AGI(agi_bp);
> > +
> > + /* Trigger inode count recalculation */
> > + xfs_force_summary_recalc(sc->mp);
> > +
> > + /* Write this to disk. */
> > + xfs_trans_buf_set_type(sc->tp, agi_bp, XFS_BLFT_AGI_BUF);
> > + xfs_trans_log_buf(sc->tp, agi_bp, 0, BBTOB(agi_bp->b_length) - 1);
> > +
> > + /* Now reinitialize the in-core counters if necessary. */
> > + pag = sc->sa.pag;
> > + sc->sa.pag->pagi_init = 1;
>
> Same s/sc->sa.pag/pag/ nit here as before.
Both fixed.
> > + pag->pagi_count = be32_to_cpu(agi->agi_count);
> > + pag->pagi_freecount = be32_to_cpu(agi->agi_freecount);
> > +
> > + return 0;
> > +}
> > +
> > +/* Repair the AGI. */
> > +int
> > +xrep_agi(
> > + struct xfs_scrub *sc)
> > +{
> > + struct xrep_find_ag_btree fab[XREP_AGI_MAX] = {
> > + [XREP_AGI_INOBT] = {
> > + .rmap_owner = XFS_RMAP_OWN_INOBT,
> > + .buf_ops = &xfs_inobt_buf_ops,
> > + .magic = XFS_IBT_CRC_MAGIC,
> > + },
> > + [XREP_AGI_FINOBT] = {
> > + .rmap_owner = XFS_RMAP_OWN_INOBT,
> > + .buf_ops = &xfs_inobt_buf_ops,
> > + .magic = XFS_FIBT_CRC_MAGIC,
> > + },
> > + [XREP_AGI_END] = {
> > + .buf_ops = NULL
> > + },
> > + };
> > + struct xfs_agi old_agi;
>
> It's not immediately clear to me how much of a danger this is here, if
> at all, but FWIW xfs_agi is one of our larger structures at 336 bytes
> (mostly due to agi_unlinked). I'm not terribly concerned if this isn't
> currently exploding, but it might be worth thinking about another
> technique to preserve original behavior without the stack usage. Perhaps
> we could use an uncached buffer to preserve the original data and
> implement an xfs_buf_copy() helper to facilitate, for example.
It's not a huge deal since (vmap) kernel stacks are 16K(!) these days on
64-bit machines, but if it ever becomes a problem we can simply allocate
some memory in sc->buf in the setup routine.
--D
> Brian
>
> > + struct xfs_mount *mp = sc->mp;
> > + struct xfs_buf *agi_bp;
> > + struct xfs_agi *agi;
> > + 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);
> > + /*
> > + * Make sure we have the AGI buffer, as scrub might have decided it
> > + * was corrupt after xfs_ialloc_read_agi failed with -EFSCORRUPTED.
> > + */
> > + error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
> > + XFS_AG_DADDR(mp, sc->sa.agno, XFS_AGI_DADDR(mp)),
> > + XFS_FSS_TO_BB(mp, 1), 0, &agi_bp, NULL);
> > + if (error)
> > + return error;
> > + agi_bp->b_ops = &xfs_agi_buf_ops;
> > + agi = XFS_BUF_TO_AGI(agi_bp);
> > +
> > + /* Find the AGI btree roots. */
> > + error = xrep_agi_find_btrees(sc, fab);
> > + if (error)
> > + return error;
> > +
> > + /* Start rewriting the header and implant the btrees we found. */
> > + xrep_agi_init_header(sc, agi_bp, &old_agi);
> > + xrep_agi_set_roots(sc, agi, fab);
> > + error = xrep_agi_calc_from_btrees(sc, agi_bp);
> > + if (error)
> > + goto out_revert;
> > +
> > + /* Reinitialize in-core state. */
> > + return xrep_agi_commit_new(sc, agi_bp, &old_agi);
> > +
> > +out_revert:
> > + /* Mark the incore AGI state stale and revert the AGI. */
> > + sc->sa.pag->pagi_init = 0;
> > + memcpy(agi, &old_agi, sizeof(old_agi));
> > + return error;
> > +}
> > diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h
> > index 1d283360b5ab..9de321eee4ab 100644
> > --- a/fs/xfs/scrub/repair.h
> > +++ b/fs/xfs/scrub/repair.h
> > @@ -60,6 +60,7 @@ 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);
> > +int xrep_agi(struct xfs_scrub *sc);
> >
> > #else
> >
> > @@ -85,6 +86,7 @@ xrep_calc_ag_resblks(
> > #define xrep_superblock xrep_notsupported
> > #define xrep_agf xrep_notsupported
> > #define xrep_agfl xrep_notsupported
> > +#define xrep_agi xrep_notsupported
> >
> > #endif /* CONFIG_XFS_ONLINE_REPAIR */
> >
> > diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
> > index 2670f4cf62f4..4bfae1e61d30 100644
> > --- a/fs/xfs/scrub/scrub.c
> > +++ b/fs/xfs/scrub/scrub.c
> > @@ -226,7 +226,7 @@ static const struct xchk_meta_ops meta_scrub_ops[] = {
> > .type = ST_PERAG,
> > .setup = xchk_setup_fs,
> > .scrub = xchk_agi,
> > - .repair = xrep_notsupported,
> > + .repair = xrep_agi,
> > },
> > [XFS_SCRUB_TYPE_BNOBT] = { /* bnobt */
> > .type = ST_PERAG,
> >
> > --
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