On Sat, Jan 09, 2021 at 03:09:19AM +0800, Gao Xiang wrote:
> As the first step of shrinking, this attempts to enable shrinking
> unused space in the last allocation group by fixing up freespace
> btree, agi, agf and adjusting super block and introduce a helper
> xfs_ag_shrink_space() to fixup the last AG.
>
> This can be all done in one transaction for now, so I think no
> additional protection is needed.
>
> Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_ag.c | 72 ++++++++++++++++++++++++++++++++++++++++++
> fs/xfs/libxfs/xfs_ag.h | 2 ++
> fs/xfs/xfs_fsops.c | 69 ++++++++++++++++++++++++++++++----------
> fs/xfs/xfs_trans.c | 1 -
> 4 files changed, 126 insertions(+), 18 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
> index 9331f3516afa..bec10c85e2a9 100644
> --- a/fs/xfs/libxfs/xfs_ag.c
> +++ b/fs/xfs/libxfs/xfs_ag.c
> @@ -485,6 +485,78 @@ xfs_ag_init_headers(
> return error;
> }
>
> +int
> +xfs_ag_shrink_space(
> + struct xfs_mount *mp,
> + struct xfs_trans *tp,
> + struct aghdr_init_data *id,
> + xfs_extlen_t len)
> +{
> + struct xfs_buf *agibp, *agfbp;
> + struct xfs_agi *agi;
> + struct xfs_agf *agf;
> + int error, err2;
> + struct xfs_alloc_arg args = {
> + .tp = tp,
> + .mp = mp,
> + .type = XFS_ALLOCTYPE_THIS_BNO,
> + .minlen = len,
> + .maxlen = len,
> + .oinfo = XFS_RMAP_OINFO_SKIP_UPDATE,
> + .resv = XFS_AG_RESV_NONE,
> + .prod = 1
> + };
> +
> + ASSERT(id->agno == mp->m_sb.sb_agcount - 1);
> + error = xfs_ialloc_read_agi(mp, tp, id->agno, &agibp);
> + if (error)
> + return error;
> +
> + agi = agibp->b_addr;
> +
> + error = xfs_alloc_read_agf(mp, tp, id->agno, 0, &agfbp);
> + if (error)
> + return error;
> +
> + args.fsbno = XFS_AGB_TO_FSB(mp, id->agno,
> + be32_to_cpu(agi->agi_length) - len);
> +
> + /* remove the preallocations before allocation and re-establish then */
> + error = xfs_ag_resv_free(agibp->b_pag);
> + if (error)
> + return error;
> +
> + /* internal log shouldn't also show up in the free space btrees */
> + error = xfs_alloc_vextent(&args);
> + if (error)
> + goto out;
> +
> + if (args.agbno == NULLAGBLOCK) {
> + error = -ENOSPC;
> + goto out;
> + }
> +
> + /* Change the agi length */
> + be32_add_cpu(&agi->agi_length, -len);
> + xfs_ialloc_log_agi(tp, agibp, XFS_AGI_LENGTH);
> +
> + /* Change agf length */
> + agf = agfbp->b_addr;
> + be32_add_cpu(&agf->agf_length, -len);
> + ASSERT(agf->agf_length == agi->agi_length);
> + xfs_alloc_log_agf(tp, agfbp, XFS_AGF_LENGTH);
> +
> +out:
> + err2 = xfs_ag_resv_init(agibp->b_pag, tp);
> + if (err2 && err2 != -ENOSPC) {
> + xfs_warn(mp,
> +"Error %d reserving per-AG metadata reserve pool.", err2);
> + xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
> + return err2;
> + }
> + return error;
> +}
> +
> /*
> * Extent the AG indicated by the @id by the length passed in
> */
> diff --git a/fs/xfs/libxfs/xfs_ag.h b/fs/xfs/libxfs/xfs_ag.h
> index 5166322807e7..f3b5bbfeadce 100644
> --- a/fs/xfs/libxfs/xfs_ag.h
> +++ b/fs/xfs/libxfs/xfs_ag.h
> @@ -24,6 +24,8 @@ struct aghdr_init_data {
> };
>
> int xfs_ag_init_headers(struct xfs_mount *mp, struct aghdr_init_data *id);
> +int xfs_ag_shrink_space(struct xfs_mount *mp, struct xfs_trans *tp,
> + struct aghdr_init_data *id, xfs_extlen_t len);
> int xfs_ag_extend_space(struct xfs_mount *mp, struct xfs_trans *tp,
> struct aghdr_init_data *id, xfs_extlen_t len);
> int xfs_ag_get_geometry(struct xfs_mount *mp, xfs_agnumber_t agno,
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index a792d1f0ac55..eea38395e804 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -79,19 +79,22 @@ xfs_growfs_data_private(
> xfs_rfsblock_t delta;
> xfs_agnumber_t oagcount;
> struct xfs_trans *tp;
> + bool extend;
> struct aghdr_init_data id = {};
>
> nb = in->newblocks;
> - if (nb < mp->m_sb.sb_dblocks)
> - return -EINVAL;
> - if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
> + error = xfs_sb_validate_fsb_count(&mp->m_sb, nb);
> + if (error)
> return error;
> - error = xfs_buf_read_uncached(mp->m_ddev_targp,
> +
> + if (nb > mp->m_sb.sb_dblocks) {
> + error = xfs_buf_read_uncached(mp->m_ddev_targp,
> XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
> XFS_FSS_TO_BB(mp, 1), 0, &bp, NULL);
> - if (error)
> - return error;
> - xfs_buf_relse(bp);
> + if (error)
> + return error;
> + xfs_buf_relse(bp);
> + }
>
> delta = nb; /* use delta as a temporary here */
Yikes, can this become a separate variable please?
> nb_mod = do_div(delta, mp->m_sb.sb_agblocks);
> @@ -99,10 +102,18 @@ xfs_growfs_data_private(
> if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) {
> nagcount--;
> nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks;
> - if (nb < mp->m_sb.sb_dblocks)
> + if (nagcount < 2)
> return -EINVAL;
> }
> - delta = nb - mp->m_sb.sb_dblocks;
> +
> + if (nb > mp->m_sb.sb_dblocks) {
> + delta = nb - mp->m_sb.sb_dblocks;
> + extend = true;
> + } else {
> + delta = mp->m_sb.sb_dblocks - nb;
> + extend = false;
/me wonders why delta isn't simply int64_t, and then you can do things
like:
if (delta > 0)
growfs
else if (delta < 0)
shrinkfs
?
> + }
> +
> oagcount = mp->m_sb.sb_agcount;
>
> /* allocate the new per-ag structures */
> @@ -110,22 +121,34 @@ xfs_growfs_data_private(
> error = xfs_initialize_perag(mp, nagcount, &nagimax);
> if (error)
> return error;
> + } else if (nagcount != oagcount) {
> + /* TODO: shrinking the entire AGs hasn't yet completed */
> + return -EINVAL;
> }
>
> error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growdata,
> - XFS_GROWFS_SPACE_RES(mp), 0, XFS_TRANS_RESERVE, &tp);
> + (extend ? XFS_GROWFS_SPACE_RES(mp) : delta), 0,
> + XFS_TRANS_RESERVE, &tp);
> if (error)
> return error;
>
> - error = xfs_resizefs_init_new_ags(mp, &id, oagcount, nagcount, &delta);
> - if (error)
> - goto out_trans_cancel;
> -
> + if (extend) {
> + error = xfs_resizefs_init_new_ags(mp, &id, oagcount,
> + nagcount, &delta);
> + if (error)
> + goto out_trans_cancel;
> + }
> xfs_trans_agblocks_delta(tp, id.nfree);
>
> - /* If there are new blocks in the old last AG, extend it. */
> + /* If there are some blocks in the last AG, resize it. */
> if (delta) {
> - error = xfs_ag_extend_space(mp, tp, &id, delta);
> + if (extend) {
> + error = xfs_ag_extend_space(mp, tp, &id, delta);
> + } else {
> + id.agno = nagcount - 1;
> + error = xfs_ag_shrink_space(mp, tp, &id, delta);
> + }
> +
> if (error)
> goto out_trans_cancel;
> }
> @@ -137,11 +160,19 @@ xfs_growfs_data_private(
> */
> if (nagcount > oagcount)
> xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount);
> - if (nb > mp->m_sb.sb_dblocks)
> + if (nb != mp->m_sb.sb_dblocks)
> xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS,
> nb - mp->m_sb.sb_dblocks);
> if (id.nfree)
> xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, id.nfree);
> +
> + /*
> + * update in-core counters (especially sb_fdblocks) now
> + * so xfs_validate_sb_write() can pass.
> + */
> + if (xfs_sb_version_haslazysbcount(&mp->m_sb))
> + xfs_log_sb(tp);
> +
> xfs_trans_set_sync(tp);
> error = xfs_trans_commit(tp);
> if (error)
> @@ -178,6 +209,10 @@ xfs_growfs_data_private(
> return error;
>
> out_trans_cancel:
> + if (!extend && (tp->t_flags & XFS_TRANS_DIRTY)) {
> + xfs_trans_commit(tp);
> + return error;
When do we encounter the (!extend && DIRTY && cancelled) state?
--D
> + }
> xfs_trans_cancel(tp);
> return error;
> }
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index e72730f85af1..fd2cbf414b80 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -419,7 +419,6 @@ xfs_trans_mod_sb(
> tp->t_res_frextents_delta += delta;
> break;
> case XFS_TRANS_SB_DBLOCKS:
> - ASSERT(delta > 0);
> tp->t_dblocks_delta += delta;
> break;
> case XFS_TRANS_SB_AGCOUNT:
> --
> 2.27.0
>
