Hi Darrick,
On Wed, Mar 24, 2021 at 10:34:38AM -0700, Darrick J. Wong wrote:
> On Wed, Mar 24, 2021 at 09:06:20AM +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 use 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.
> >
> > Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
> > ---
> > fs/xfs/xfs_fsops.c | 84 +++++++++++++++++++++++++++-------------------
> > fs/xfs/xfs_trans.c | 1 -
> > 2 files changed, 50 insertions(+), 35 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> > index d1ba04124c28..9457b0691ece 100644
> > --- a/fs/xfs/xfs_fsops.c
> > +++ b/fs/xfs/xfs_fsops.c
> > @@ -91,23 +91,25 @@ xfs_growfs_data_private(
> > xfs_agnumber_t nagcount;
> > xfs_agnumber_t nagimax = 0;
> > xfs_rfsblock_t nb, nb_div, nb_mod;
> > - xfs_rfsblock_t delta;
> > + int64_t delta;
> > bool lastag_extended;
> > xfs_agnumber_t oagcount;
> > struct xfs_trans *tp;
> > 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);
> > + }
> >
> > nb_div = nb;
> > nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks);
> > @@ -115,10 +117,16 @@ 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)
> > - return -EINVAL;
> > }
> > delta = nb - mp->m_sb.sb_dblocks;
> > + /*
> > + * Reject filesystems with a single AG because they are not
> > + * supported, and reject a shrink operation that would cause a
> > + * filesystem to become unsupported.
> > + */
> > + if (delta < 0 && nagcount < 2)
> > + return -EINVAL;
> > +
> > oagcount = mp->m_sb.sb_agcount;
> >
> > /* allocate the new per-ag structures */
> > @@ -126,15 +134,22 @@ 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);
> > + (delta > 0 ? XFS_GROWFS_SPACE_RES(mp) : -delta), 0,
> > + XFS_TRANS_RESERVE, &tp);
> > if (error)
> > return error;
> >
> > - error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount,
> > - delta, &lastag_extended);
> > + if (delta > 0)
> > + error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount,
> > + delta, &lastag_extended);
> > + else
> > + error = xfs_ag_shrink_space(mp, &tp, nagcount - 1, -delta);
>
> Assuming I don't hear anyone yelling NAK in the next day or so, I think
> I'll stage this for 5.13 with the following change to warn that the
> shrink feature is still EXPERIMENTAL:
>
> By the way, are you going to send a patch to shrink the realtime device
> too?
My first priority will form the formal shrink-whole-AG patchset after this
is finalized.
I have little experience about rt device, maybe leave it later.
>
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 9457b0691ece..b33c894b6cf3 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -145,11 +145,20 @@ xfs_growfs_data_private(
> if (error)
> return error;
>
> - if (delta > 0)
> + if (delta > 0) {
> error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount,
> delta, &lastag_extended);
> - else
> + } else {
> + static struct ratelimit_state shrink_warning = \
> + RATELIMIT_STATE_INIT("shrink_warning", 86400 * HZ, 1);
> + ratelimit_set_flags(&shrink_warning, RATELIMIT_MSG_ON_RELEASE);
> +
> + if (__ratelimit(&shrink_warning))
> + xfs_alert(mp,
> + "EXPERIMENTAL online shrink feature in use. Use at your own risk!");
> +
> error = xfs_ag_shrink_space(mp, &tp, nagcount - 1, -delta);
> + }
> if (error)
> goto out_trans_cancel;
I'm fine with that, thanks for updating. :)
Thanks,
Gao Xiang
>
> --D
>
> > if (error)
> > goto out_trans_cancel;
> >
> > @@ -169,28 +184,29 @@ xfs_growfs_data_private(
> > xfs_set_low_space_thresholds(mp);
> > mp->m_alloc_set_aside = xfs_alloc_set_aside(mp);
> >
> > - /*
> > - * If we expanded the last AG, free the per-AG reservation
> > - * so we can reinitialize it with the new size.
> > - */
> > - if (lastag_extended) {
> > - struct xfs_perag *pag;
> > -
> > - pag = xfs_perag_get(mp, id.agno);
> > - error = xfs_ag_resv_free(pag);
> > - xfs_perag_put(pag);
> > - if (error)
> > - return error;
> > + if (delta > 0) {
> > + /*
> > + * If we expanded the last AG, free the per-AG reservation
> > + * so we can reinitialize it with the new size.
> > + */
> > + if (lastag_extended) {
> > + struct xfs_perag *pag;
> > +
> > + pag = xfs_perag_get(mp, id.agno);
> > + error = xfs_ag_resv_free(pag);
> > + xfs_perag_put(pag);
> > + if (error)
> > + return error;
> > + }
> > + /*
> > + * Reserve AG metadata blocks. ENOSPC here does not mean there
> > + * was a growfs failure, just that there still isn't space for
> > + * new user data after the grow has been run.
> > + */
> > + error = xfs_fs_reserve_ag_blocks(mp);
> > + if (error == -ENOSPC)
> > + error = 0;
> > }
> > -
> > - /*
> > - * Reserve AG metadata blocks. ENOSPC here does not mean there was a
> > - * growfs failure, just that there still isn't space for new user data
> > - * after the grow has been run.
> > - */
> > - error = xfs_fs_reserve_ag_blocks(mp);
> > - if (error == -ENOSPC)
> > - error = 0;
> > return error;
> >
> > out_trans_cancel:
> > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> > index b22a09e9daee..052274321993 100644
> > --- a/fs/xfs/xfs_trans.c
> > +++ b/fs/xfs/xfs_trans.c
> > @@ -436,7 +436,6 @@ 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
> >
>
