GFS2: Use RCU/hlist_bl based hash for quotas
Prior to this patch, GFS2 kept all the quotas for each
super block in a single linked list. This is rather slow
when there are large numbers of quotas.
This patch introduces a hlist_bl based hash table, similar
to the one used for glocks. The initial look up of the quota
is now lockless in the case where it is already cached,
although we still have to take the per quota spinlock in
order to bump the ref count. Either way though, this is a
big improvement on what was there before.
The qd_lock and the per super block list is preserved, for
the time being. However it is intended that since this is no
longer used for its original role, it should be possible to
shrink the number of items on that list in due course and
remove the requirement to take qd_lock in qd_get.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Abhijith Das <adas@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index a99f60c..59d99ec 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -428,10 +428,13 @@
};
struct gfs2_quota_data {
+ struct hlist_bl_node qd_hlist;
struct list_head qd_list;
struct kqid qd_id;
+ struct gfs2_sbd *qd_sbd;
struct lockref qd_lockref;
struct list_head qd_lru;
+ unsigned qd_hash;
unsigned long qd_flags; /* QDF_... */
@@ -450,6 +453,7 @@
u64 qd_sync_gen;
unsigned long qd_last_warn;
+ struct rcu_head qd_rcu;
};
struct gfs2_trans {