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dm persistent data: remove space map ref_count entries if redundant 

Save space by removing entries from the space map ref_count tree if
they're no longer needed.

Ref counts are stored in two places: a bitmap if the ref_count is
below 3, or a btree of uint32_t if 3 or above.

When a ref_count that was above 3 drops below we can remove it from
the tree and save some metadata space.  This removal was commented out
before because I was unsure why this was causing under-populated btree
nodes.  Earlier patches have fixed this issue.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Joe Thornber 2012-03-28 18:41:27 +01:00 committed by Alasdair G Kergon
parent 905e51b39a
commit 71fd5ae25d
1 changed files with 0 additions and 3 deletions
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3
drivers/md/persistent-data/dm-space-map-common.c
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@ -405,8 +405,6 @@ int sm_ll_insert(struct ll_disk *ll, dm_block_t b,
if (r < 0)
return r;
#if 0
/* FIXME: dm_btree_remove doesn't handle this yet */
if (old > 2) {
r = dm_btree_remove(&ll->ref_count_info,
ll->ref_count_root,
@ -414,7 +412,6 @@ int sm_ll_insert(struct ll_disk *ll, dm_block_t b,
if (r)
return r;
}
#endif
} else {
__le32 le_rc = cpu_to_le32(ref_count);