gfs2: Add per-reservation reserved block accounting

Add a rs_reserved field to struct gfs2_blkreserv to keep track of the number of
blocks reserved by this particular reservation, and a rd_reserved field to
struct gfs2_rgrpd to keep track of the total number of reserved blocks in the
resource group.  Those blocks are exclusively reserved, as opposed to the
rs_requested / rd_requested blocks which are tracked in the reservation tree
(rd_rstree) and which can be stolen if necessary.

When making a reservation with gfs2_inplace_reserve, rs_reserved is set to
somewhere between ap->min_target and ap->target depending on the number of free
blocks in the resource group.  When allocating blocks with gfs2_alloc_blocks,
rs_reserved is decremented accordingly.  Eventually, any reserved but not
consumed blocks are returned to the resource group by gfs2_inplace_release.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 3922b26264f5..802bc15f9f11 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -84,6 +84,7 @@ static void maybe_release_space(struct gfs2_bufdata *bd)
 	       bd->bd_bh->b_data + bi->bi_offset, bi->bi_bytes);
 	clear_bit(GBF_FULL, &bi->bi_flags);
 	rgd->rd_free_clone = rgd->rd_free;
+	BUG_ON(rgd->rd_free_clone < rgd->rd_reserved);
 	rgd->rd_extfail_pt = rgd->rd_free;
 }