[PATCH 02/20] staging: lustre: convert lov_pool to use rhashtable
From: NeilBrown
Date: Wed Apr 11 2018 - 17:55:34 EST
The pools hashtable can be implemented using
the rhashtable implementation in lib.
This has the benefit that lookups are lock-free.
We need to use kfree_rcu() to free a pool so
that a lookup racing with a deletion will not access
freed memory.
rhashtable has no combined lookup-and-delete interface,
but as the lookup is lockless and the chains are short,
this brings little cost. Even if a lookup finds a pool,
we must be prepared for the delete to fail to find it,
as we might race with another thread doing a delete.
We use atomic_inc_not_zero() after finding a pool in the
hash table and if that fails, we must have raced with a
deletion, so we treat the lookup as a failure.
Use hashlen_string() rather than a hand-crafted hash
function.
Note that the pool_name, and the search key, are
guaranteed to be nul terminated.
Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
drivers/staging/lustre/lustre/include/obd.h | 4 -
.../staging/lustre/lustre/include/obd_support.h | 3
drivers/staging/lustre/lustre/lov/lov_internal.h | 11 +
drivers/staging/lustre/lustre/lov/lov_obd.c | 12 +-
drivers/staging/lustre/lustre/lov/lov_pool.c | 159 ++++++++------------
5 files changed, 80 insertions(+), 109 deletions(-)
diff --git a/drivers/staging/lustre/lustre/include/obd.h b/drivers/staging/lustre/lustre/include/obd.h
index f1233ca7d337..ad265db48b76 100644
--- a/drivers/staging/lustre/lustre/include/obd.h
+++ b/drivers/staging/lustre/lustre/include/obd.h
@@ -46,6 +46,8 @@
#include <lustre_intent.h>
#include <cl_object.h>
+#include <linux/rhashtable.h>
+
#define MAX_OBD_DEVICES 8192
struct osc_async_rc {
@@ -383,7 +385,7 @@ struct lov_obd {
__u32 lov_tgt_size; /* size of tgts array */
int lov_connects;
int lov_pool_count;
- struct cfs_hash *lov_pools_hash_body; /* used for key access */
+ struct rhashtable lov_pools_hash_body; /* used for key access */
struct list_head lov_pool_list; /* used for sequential access */
struct dentry *lov_pool_debugfs_entry;
enum lustre_sec_part lov_sp_me;
diff --git a/drivers/staging/lustre/lustre/include/obd_support.h b/drivers/staging/lustre/lustre/include/obd_support.h
index aebcab191442..730a6ee71565 100644
--- a/drivers/staging/lustre/lustre/include/obd_support.h
+++ b/drivers/staging/lustre/lustre/include/obd_support.h
@@ -61,9 +61,6 @@ extern atomic_long_t obd_dirty_transit_pages;
extern char obd_jobid_var[];
/* Some hash init argument constants */
-#define HASH_POOLS_BKT_BITS 3
-#define HASH_POOLS_CUR_BITS 3
-#define HASH_POOLS_MAX_BITS 7
#define HASH_UUID_BKT_BITS 5
#define HASH_UUID_CUR_BITS 7
#define HASH_UUID_MAX_BITS 12
diff --git a/drivers/staging/lustre/lustre/lov/lov_internal.h b/drivers/staging/lustre/lustre/lov/lov_internal.h
index 27f60dd7ab9a..47042f27ca90 100644
--- a/drivers/staging/lustre/lustre/lov/lov_internal.h
+++ b/drivers/staging/lustre/lustre/lov/lov_internal.h
@@ -149,11 +149,16 @@ struct pool_desc {
char pool_name[LOV_MAXPOOLNAME + 1];
struct ost_pool pool_obds;
atomic_t pool_refcount;
- struct hlist_node pool_hash; /* access by poolname */
- struct list_head pool_list; /* serial access */
+ struct rhash_head pool_hash; /* access by poolname */
+ union {
+ struct list_head pool_list; /* serial access */
+ struct rcu_head rcu; /* delayed free */
+ };
struct dentry *pool_debugfs_entry; /* file in debugfs */
struct obd_device *pool_lobd; /* owner */
};
+int lov_pool_hash_init(struct rhashtable *tbl);
+void lov_pool_hash_destroy(struct rhashtable *tbl);
struct lov_request {
struct obd_info rq_oi;
@@ -241,8 +246,6 @@ void lprocfs_lov_init_vars(struct lprocfs_static_vars *lvars);
/* lov_cl.c */
extern struct lu_device_type lov_device_type;
-/* pools */
-extern struct cfs_hash_ops pool_hash_operations;
/* ost_pool methods */
int lov_ost_pool_init(struct ost_pool *op, unsigned int count);
int lov_ost_pool_extend(struct ost_pool *op, unsigned int min_count);
diff --git a/drivers/staging/lustre/lustre/lov/lov_obd.c b/drivers/staging/lustre/lustre/lov/lov_obd.c
index 355e87ecc62d..94da35e673f7 100644
--- a/drivers/staging/lustre/lustre/lov/lov_obd.c
+++ b/drivers/staging/lustre/lustre/lov/lov_obd.c
@@ -795,15 +795,11 @@ int lov_setup(struct obd_device *obd, struct lustre_cfg *lcfg)
init_rwsem(&lov->lov_notify_lock);
- lov->lov_pools_hash_body = cfs_hash_create("POOLS", HASH_POOLS_CUR_BITS,
- HASH_POOLS_MAX_BITS,
- HASH_POOLS_BKT_BITS, 0,
- CFS_HASH_MIN_THETA,
- CFS_HASH_MAX_THETA,
- &pool_hash_operations,
- CFS_HASH_DEFAULT);
INIT_LIST_HEAD(&lov->lov_pool_list);
lov->lov_pool_count = 0;
+ rc = lov_pool_hash_init(&lov->lov_pools_hash_body);
+ if (rc)
+ goto out;
rc = lov_ost_pool_init(&lov->lov_packed, 0);
if (rc)
goto out;
@@ -839,7 +835,7 @@ static int lov_cleanup(struct obd_device *obd)
/* coverity[overrun-buffer-val] */
lov_pool_del(obd, pool->pool_name);
}
- cfs_hash_putref(lov->lov_pools_hash_body);
+ lov_pool_hash_destroy(&lov->lov_pools_hash_body);
lov_ost_pool_free(&lov->lov_packed);
lprocfs_obd_cleanup(obd);
diff --git a/drivers/staging/lustre/lustre/lov/lov_pool.c b/drivers/staging/lustre/lustre/lov/lov_pool.c
index ecd9329cd073..b673b4fd305b 100644
--- a/drivers/staging/lustre/lustre/lov/lov_pool.c
+++ b/drivers/staging/lustre/lustre/lov/lov_pool.c
@@ -49,6 +49,28 @@
#define pool_tgt(_p, _i) \
_p->pool_lobd->u.lov.lov_tgts[_p->pool_obds.op_array[_i]]
+static u32 pool_hashfh(const void *data, u32 len, u32 seed)
+{
+ const char *pool_name = data;
+ return hashlen_hash(hashlen_string((void*)(unsigned long)seed, pool_name));
+}
+
+static int pool_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+ const struct pool_desc *pool = obj;
+ const char *pool_name = arg->key;
+ return strcmp(pool_name, pool->pool_name);
+}
+
+static const struct rhashtable_params pools_hash_params = {
+ .key_len = 1, /* actually variable */
+ .key_offset = offsetof(struct pool_desc, pool_name),
+ .head_offset = offsetof(struct pool_desc, pool_hash),
+ .hashfn = pool_hashfh,
+ .obj_cmpfn = pool_cmpfn,
+ .automatic_shrinking = true,
+};
+
static void lov_pool_getref(struct pool_desc *pool)
{
CDEBUG(D_INFO, "pool %p\n", pool);
@@ -59,96 +81,13 @@ void lov_pool_putref(struct pool_desc *pool)
{
CDEBUG(D_INFO, "pool %p\n", pool);
if (atomic_dec_and_test(&pool->pool_refcount)) {
- LASSERT(hlist_unhashed(&pool->pool_hash));
LASSERT(list_empty(&pool->pool_list));
LASSERT(!pool->pool_debugfs_entry);
lov_ost_pool_free(&pool->pool_obds);
- kfree(pool);
- }
-}
-
-static void lov_pool_putref_locked(struct pool_desc *pool)
-{
- CDEBUG(D_INFO, "pool %p\n", pool);
- LASSERT(atomic_read(&pool->pool_refcount) > 1);
-
- atomic_dec(&pool->pool_refcount);
-}
-
-/*
- * hash function using a Rotating Hash algorithm
- * Knuth, D. The Art of Computer Programming,
- * Volume 3: Sorting and Searching,
- * Chapter 6.4.
- * Addison Wesley, 1973
- */
-static __u32 pool_hashfn(struct cfs_hash *hash_body, const void *key,
- unsigned int mask)
-{
- int i;
- __u32 result;
- char *poolname;
-
- result = 0;
- poolname = (char *)key;
- for (i = 0; i < LOV_MAXPOOLNAME; i++) {
- if (poolname[i] == '\0')
- break;
- result = (result << 4) ^ (result >> 28) ^ poolname[i];
+ kfree_rcu(pool, rcu);
}
- return (result % mask);
-}
-
-static void *pool_key(struct hlist_node *hnode)
-{
- struct pool_desc *pool;
-
- pool = hlist_entry(hnode, struct pool_desc, pool_hash);
- return pool->pool_name;
-}
-
-static int pool_hashkey_keycmp(const void *key, struct hlist_node *compared_hnode)
-{
- char *pool_name;
- struct pool_desc *pool;
-
- pool_name = (char *)key;
- pool = hlist_entry(compared_hnode, struct pool_desc, pool_hash);
- return !strncmp(pool_name, pool->pool_name, LOV_MAXPOOLNAME);
-}
-
-static void *pool_hashobject(struct hlist_node *hnode)
-{
- return hlist_entry(hnode, struct pool_desc, pool_hash);
-}
-
-static void pool_hashrefcount_get(struct cfs_hash *hs, struct hlist_node *hnode)
-{
- struct pool_desc *pool;
-
- pool = hlist_entry(hnode, struct pool_desc, pool_hash);
- lov_pool_getref(pool);
-}
-
-static void pool_hashrefcount_put_locked(struct cfs_hash *hs,
- struct hlist_node *hnode)
-{
- struct pool_desc *pool;
-
- pool = hlist_entry(hnode, struct pool_desc, pool_hash);
- lov_pool_putref_locked(pool);
}
-struct cfs_hash_ops pool_hash_operations = {
- .hs_hash = pool_hashfn,
- .hs_key = pool_key,
- .hs_keycmp = pool_hashkey_keycmp,
- .hs_object = pool_hashobject,
- .hs_get = pool_hashrefcount_get,
- .hs_put_locked = pool_hashrefcount_put_locked,
-
-};
-
/*
* pool debugfs seq_file methods
*/
@@ -396,6 +335,23 @@ int lov_ost_pool_free(struct ost_pool *op)
return 0;
}
+static void
+pools_hash_exit(void *vpool, void *data)
+{
+ struct pool_desc *pool = vpool;
+ lov_pool_putref(pool);
+}
+
+int lov_pool_hash_init(struct rhashtable *tbl)
+{
+ return rhashtable_init(tbl, &pools_hash_params);
+}
+
+void lov_pool_hash_destroy(struct rhashtable *tbl)
+{
+ rhashtable_free_and_destroy(tbl, pools_hash_exit, NULL);
+}
+
int lov_pool_new(struct obd_device *obd, char *poolname)
{
struct lov_obd *lov;
@@ -421,8 +377,6 @@ int lov_pool_new(struct obd_device *obd, char *poolname)
if (rc)
goto out_err;
- INIT_HLIST_NODE(&new_pool->pool_hash);
-
/* get ref for debugfs file */
lov_pool_getref(new_pool);
new_pool->pool_debugfs_entry = ldebugfs_add_simple(
@@ -443,11 +397,16 @@ int lov_pool_new(struct obd_device *obd, char *poolname)
lov->lov_pool_count++;
spin_unlock(&obd->obd_dev_lock);
- /* add to find only when it fully ready */
- rc = cfs_hash_add_unique(lov->lov_pools_hash_body, poolname,
- &new_pool->pool_hash);
+ /* Add to hash table only when it is fully ready. */
+ rc = rhashtable_lookup_insert_fast(&lov->lov_pools_hash_body,
+ &new_pool->pool_hash, pools_hash_params);
if (rc) {
- rc = -EEXIST;
+ if (rc != -EEXIST)
+ /*
+ * Hide -E2BIG and -EBUSY which
+ * are not helpful.
+ */
+ rc = -ENOMEM;
goto out_err;
}
@@ -476,7 +435,13 @@ int lov_pool_del(struct obd_device *obd, char *poolname)
lov = &obd->u.lov;
/* lookup and kill hash reference */
- pool = cfs_hash_del_key(lov->lov_pools_hash_body, poolname);
+ rcu_read_lock();
+ pool = rhashtable_lookup(&lov->lov_pools_hash_body, poolname, pools_hash_params);
+ if (pool)
+ if (rhashtable_remove_fast(&lov->lov_pools_hash_body,
+ &pool->pool_hash, pools_hash_params) != 0)
+ pool = NULL;
+ rcu_read_unlock();
if (!pool)
return -ENOENT;
@@ -507,7 +472,11 @@ int lov_pool_add(struct obd_device *obd, char *poolname, char *ostname)
lov = &obd->u.lov;
- pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
+ rcu_read_lock();
+ pool = rhashtable_lookup(&lov->lov_pools_hash_body, poolname, pools_hash_params);
+ if (pool && !atomic_inc_not_zero(&pool->pool_refcount))
+ pool = NULL;
+ rcu_read_unlock();
if (!pool)
return -ENOENT;
@@ -551,7 +520,11 @@ int lov_pool_remove(struct obd_device *obd, char *poolname, char *ostname)
lov = &obd->u.lov;
- pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
+ rcu_read_lock();
+ pool = rhashtable_lookup(&lov->lov_pools_hash_body, poolname, pools_hash_params);
+ if (pool && !atomic_inc_not_zero(&pool->pool_refcount))
+ pool = NULL;
+ rcu_read_unlock();
if (!pool)
return -ENOENT;