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?
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;
--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
>
