linux-kernel - [PATCH 06/20] staging: lustre: ldlm: add a counter to the per-namespace data

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Message-ID: <152348368872.12394.16831797606945626384.stgit@noble>
Date:   Thu, 12 Apr 2018 07:54:48 +1000
From:   NeilBrown <neilb@...e.com>
To:     Oleg Drokin <oleg.drokin@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        James Simmons <jsimmons@...radead.org>,
        Andreas Dilger <andreas.dilger@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: [PATCH 06/20] staging: lustre: ldlm: add a counter to the
 per-namespace data

When we change the resource hash to rhashtable we won't have
a per-bucket counter.  We could use the nelems global counter,
but ldlm_resource goes to some trouble to avoid having any
table-wide atomics, and hopefully rhashtable will grow the
ability to disable the global counter in the near future.
Having a counter we control makes it easier to manage the
back-reference to the namespace when there is anything in the
hash table.

So add a counter to the ldlm_ns_bucket.

Signed-off-by: NeilBrown <neilb@...e.com>
---
 drivers/staging/lustre/lustre/include/lustre_dlm.h |    2 ++
 drivers/staging/lustre/lustre/ldlm/ldlm_resource.c |   10 +++++-----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/lustre/lustre/include/lustre_dlm.h b/drivers/staging/lustre/lustre/include/lustre_dlm.h
index 395d50160dcc..ab90abe1c2d8 100644
--- a/drivers/staging/lustre/lustre/include/lustre_dlm.h
+++ b/drivers/staging/lustre/lustre/include/lustre_dlm.h
@@ -309,6 +309,8 @@ struct ldlm_ns_bucket {
 	 * fact the network or overall system load is at fault
 	 */
 	struct adaptive_timeout     nsb_at_estimate;
+	/* counter of entries in this bucket */
+	atomic_t		nsb_count;
 };
 
 enum {
diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c b/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
index 927544f01adc..669556420bdf 100644
--- a/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
+++ b/drivers/staging/lustre/lustre/ldlm/ldlm_resource.c
@@ -181,12 +181,11 @@ static ssize_t resource_count_show(struct kobject *kobj, struct attribute *attr,
 	struct ldlm_namespace *ns = container_of(kobj, struct ldlm_namespace,
 						 ns_kobj);
 	__u64		  res = 0;
-	struct cfs_hash_bd	  bd;
 	int		    i;
 
 	/* result is not strictly consistent */
-	cfs_hash_for_each_bucket(ns->ns_rs_hash, &bd, i)
-		res += cfs_hash_bd_count_get(&bd);
+	for (i = 0; i < (1 << ns->ns_bucket_bits); i++)
+		res += atomic_read(&ns->ns_rs_buckets[i].nsb_count);
 	return sprintf(buf, "%lld\n", res);
 }
 LUSTRE_RO_ATTR(resource_count);
@@ -668,6 +667,7 @@ struct ldlm_namespace *ldlm_namespace_new(struct obd_device *obd, char *name,
 		struct ldlm_ns_bucket *nsb = &ns->ns_rs_buckets[idx];
 		at_init(&nsb->nsb_at_estimate, ldlm_enqueue_min, 0);
 		nsb->nsb_namespace = ns;
+		atomic_set(&nsb->nsb_count, 0);
 	}
 
 	ns->ns_obd      = obd;
@@ -1144,7 +1144,7 @@ ldlm_resource_get(struct ldlm_namespace *ns, struct ldlm_resource *parent,
 	}
 	/* We won! Let's add the resource. */
 	cfs_hash_bd_add_locked(ns->ns_rs_hash, &bd, &res->lr_hash);
-	if (cfs_hash_bd_count_get(&bd) == 1)
+	if (atomic_inc_return(&res->lr_ns_bucket->nsb_count) == 1)
 		ns_refcount = ldlm_namespace_get_return(ns);
 
 	cfs_hash_bd_unlock(ns->ns_rs_hash, &bd, 1);
@@ -1202,7 +1202,7 @@ static void __ldlm_resource_putref_final(struct cfs_hash_bd *bd,
 	cfs_hash_bd_unlock(ns->ns_rs_hash, bd, 1);
 	if (ns->ns_lvbo && ns->ns_lvbo->lvbo_free)
 		ns->ns_lvbo->lvbo_free(res);
-	if (cfs_hash_bd_count_get(bd) == 0)
+	if (atomic_dec_and_test(&nsb->nsb_count))
 		ldlm_namespace_put(ns);
 	kmem_cache_free(ldlm_resource_slab, res);
 }