[Cluster-devel] [GFS2 PATCH] gfs2: eliminate rs_inum and reduce the size of gfs2 inodes

[Andreas Gruenbacher]

On 13 June 2018 at 15:58, Bob Peterson <rpeterso at redhat.com> wrote:
> Hi,
>
> Before this patch, block reservations kept track of the inode
> number. At one point, that was a valid thing to do. However, since
> we made the reservation a part of the inode (rather than a pointer
> to a separate allocated object) the reservation can determine the
> inode number by using container_of. This saves us a little memory
> in our inode.
>
> Signed-off-by: Bob Peterson <rpeterso at redhat.com>
> ---
>  fs/gfs2/incore.h     | 1 -
>  fs/gfs2/rgrp.c       | 5 +++--
>  fs/gfs2/trace_gfs2.h | 3 ++-
>  3 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
> index d2ad817e089f..e9cd2cc292d3 100644
> --- a/fs/gfs2/incore.h
> +++ b/fs/gfs2/incore.h
> @@ -295,7 +295,6 @@ struct gfs2_blkreserv {
>         struct rb_node rs_node;       /* link to other block reservations */
>         struct gfs2_rbm rs_rbm;       /* Start of reservation */
>         u32 rs_free;                  /* how many blocks are still free */
> -       u64 rs_inum;                  /* Inode number for reservation */
>  };
>
>  /*
> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
> index 6bc5cfe710d1..7a001f6e8aee 100644
> --- a/fs/gfs2/rgrp.c
> +++ b/fs/gfs2/rgrp.c
> @@ -607,8 +607,10 @@ int gfs2_rsqa_alloc(struct gfs2_inode *ip)
>
>  static void dump_rs(struct seq_file *seq, const struct gfs2_blkreserv *rs)
>  {
> +       struct gfs2_inode *ip = container_of(rs, struct gfs2_inode, i_res);
> +
>         gfs2_print_dbg(seq, "  B: n:%llu s:%llu b:%u f:%u\n",
> -                      (unsigned long long)rs->rs_inum,
> +                      (unsigned long long)ip->i_no_addr,
>                        (unsigned long long)gfs2_rbm_to_block(&rs->rs_rbm),
>                        rs->rs_rbm.offset, rs->rs_free);
>  }
> @@ -1528,7 +1530,6 @@ static void rg_mblk_search(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip,
>         if (ret == 0) {
>                 rs->rs_rbm = rbm;
>                 rs->rs_free = extlen;
> -               rs->rs_inum = ip->i_no_addr;
>                 rs_insert(ip);
>         } else {
>                 if (goal == rgd->rd_last_alloc + rgd->rd_data0)
> diff --git a/fs/gfs2/trace_gfs2.h b/fs/gfs2/trace_gfs2.h
> index cb10b95efe0f..e0025258107a 100644
> --- a/fs/gfs2/trace_gfs2.h
> +++ b/fs/gfs2/trace_gfs2.h
> @@ -606,7 +606,8 @@ TRACE_EVENT(gfs2_rs,
>                 __entry->rd_addr        = rs->rs_rbm.rgd->rd_addr;
>                 __entry->rd_free_clone  = rs->rs_rbm.rgd->rd_free_clone;
>                 __entry->rd_reserved    = rs->rs_rbm.rgd->rd_reserved;
> -               __entry->inum           = rs->rs_inum;
> +               __entry->inum           = container_of(rs, struct gfs2_inode,
> +                                                      i_res)->i_no_addr;
>                 __entry->start          = gfs2_rbm_to_block(&rs->rs_rbm);
>                 __entry->free           = rs->rs_free;
>                 __entry->func           = func;
>

Reviewed-by: Andreas Gruenbacher <agruenba at redhat.com>

Thanks,
Andreas