[lustre-devel] [PATCH RFC] lustre: obd: convert obd_nid_hash to rhashtable
NeilBrown
neilb at suse.com
Sun Nov 4 15:43:25 PST 2018
On Sun, Nov 04 2018, James Simmons wrote:
>> > This patch converts the struct obd_export obd_nid_hash used by the servr
>> > to use rhltables. The reason is that the NID hash can have multiple obd
>> > exports using the same NID key. In the process we gain lockless lookup
>> > which should improve performance. This should also address the rare
>> > crashes:
>> >
>> > [<ffffffffc0913388>] ? cfs_hash_bd_from_key+0x38/0xb0 [libcfs]
>> > [74844.507416] [<ffffffffc0913425>] cfs_hash_bd_get+0x25/0x70 [libcfs]
>> > [74844.516384] [<ffffffffc09166d2>] cfs_hash_add+0x52/0x1a0 [libcfs]
>> > [74844.525211] [<ffffffffc0d8a765>] target_handle_connect+0x1fe5/0x29b0 [ptlrpc]
>> >
>> > Pre 4.8 kernels do not support rhltables so wrappers have been created.
>> >
>> > ***
>> > My testing has been positive so far but I do need to figure out the
>> > debugfs file mapping from the old libcfs hash to rhashtables.
>> >
>> > ***
>> >
>> > Signed-off-by: James Simmons <uja.ornl at yahoo.com>
>> > ---
>> > libcfs/autoconf/lustre-libcfs.m4 | 21 +++
>> > libcfs/include/libcfs/linux/linux-hash.h | 88 ++++++++++++
>> > lustre/include/lustre_export.h | 2 +-
>> > lustre/include/obd.h | 8 +-
>> > lustre/include/obd_support.h | 3 -
>> > lustre/ldlm/ldlm_flock.c | 18 ++-
>> > lustre/ldlm/ldlm_lib.c | 14 +-
>> > lustre/mdt/mdt_lproc.c | 21 ++-
>> > lustre/obdclass/genops.c | 76 ++++++-----
>> > lustre/obdclass/lprocfs_status_server.c | 133 +++++++++++-------
>> > lustre/obdclass/obd_config.c | 225 ++++++++++++++++++-------------
>> > 11 files changed, 394 insertions(+), 215 deletions(-)
>> >
>> > diff --git a/libcfs/autoconf/lustre-libcfs.m4 b/libcfs/autoconf/lustre-libcfs.m4
>> > index d437331..147ecb3 100644
>> > --- a/libcfs/autoconf/lustre-libcfs.m4
>> > +++ b/libcfs/autoconf/lustre-libcfs.m4
>> > @@ -761,6 +761,26 @@ LB_CHECK_LINUX_HEADER([linux/stringhash.h], [
>> > ]) # LIBCFS_STRINGHASH
>> >
>> > #
>> > +# LIBCFS_RHLTABLE
>> > +# Kernel version 4.8 commit ca26893f05e86497a86732768ec53cd38c0819ca
>> > +# created the rhlist interface to allow inserting duplicate objects
>> > +# into the same table.
>> > +#
>> > +AC_DEFUN([LIBCFS_RHLTABLE], [
>> > +LB_CHECK_COMPILE([if 'struct rhltable' exist],
>> > +rhtable, [
>> > + #include <linux/rhashtable.h>
>> > +],[
>> > + struct rhltable *hlt = NULL;
>> > +
>> > + rhltable_destroy(hlt);
>> > +],[
>> > + AC_DEFINE(HAVE_RHLTABLE, 1,
>> > + [struct rhltable exist])
>> > +])
>> > +]) # LIBCFS_RHLTABLE
>> > +
>> > +#
>> > # LIBCFS_STACKTRACE_OPS
>> > #
>> > # Kernel version 4.8 commit c8fe4609827aedc9c4b45de80e7cdc8ccfa8541b
>> > @@ -999,6 +1019,7 @@ LIBCFS_STACKTRACE_OPS_ADDRESS_RETURN_INT
>> > LIBCFS_GET_USER_PAGES_6ARG
>> > LIBCFS_STRINGHASH
>> > # 4.8
>> > +LIBCFS_RHLTABLE
>> > LIBCFS_STACKTRACE_OPS
>> > # 4.9
>> > LIBCFS_GET_USER_PAGES_GUP_FLAGS
>> > diff --git a/libcfs/include/libcfs/linux/linux-hash.h b/libcfs/include/libcfs/linux/linux-hash.h
>> > index 1227ec8..0453cd9 100644
>> > --- a/libcfs/include/libcfs/linux/linux-hash.h
>> > +++ b/libcfs/include/libcfs/linux/linux-hash.h
>> > @@ -38,6 +38,94 @@ u64 cfs_hashlen_string(const void *salt, const char *name);
>> > #endif
>> > #endif /* !HAVE_STRINGHASH */
>> >
>> > +#ifndef HAVE_RHLTABLE
>> > +struct rhlist_head {
>> > + struct rhash_head rhead;
>> > + struct rhlist_head __rcu *next;
>> > +};
>> > +
>> > +struct rhltable {
>> > + struct rhashtable ht;
>> > +};
>> > +
>> > +#define rhl_for_each_entry_rcu(tpos, pos, list, member) \
>> > + for (pos = list; pos && rht_entry(tpos, pos, member); \
>> > + pos = rcu_dereference_raw(pos->next))
>> > +
>> > +static inline int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
>> > +{
>> > + return rhashtable_init(&hlt->ht, params);
>> > +}
>> > +
>> > +static inline struct rhlist_head *rhltable_lookup(
>> > + struct rhltable *hlt, const void *key,
>> > + const struct rhashtable_params params)
>> > +{
>> > + struct rhashtable *ht = &hlt->ht;
>> > + struct rhashtable_compare_arg arg = {
>> > + .ht = ht,
>> > + .key = key,
>> > + };
>> > + struct bucket_table *tbl;
>> > + struct rhash_head *he;
>> > + unsigned int hash;
>> > +
>> > + tbl = rht_dereference_rcu(ht->tbl, ht);
>> > +restart:
>> > + hash = rht_key_hashfn(ht, tbl, key, params);
>> > + rht_for_each_rcu(he, tbl, hash) {
>> > + if (params.obj_cmpfn ?
>> > + params.obj_cmpfn(&arg, rht_obj(ht, he)) :
>> > + rhashtable_compare(&arg, rht_obj(ht, he)))
>> > + continue;
>> > + return he ? container_of(he, struct rhlist_head, rhead) : NULL;
>> > + }
>> > +
>> > + /* Ensure we see any new tables. */
>> > + smp_rmb();
>> > +
>> > + tbl = rht_dereference_rcu(tbl->future_tbl, ht);
>> > + if (unlikely(tbl))
>> > + goto restart;
>> > +
>> > + return NULL;
>> > +}
>> > +
>> > +static inline int rhltable_insert_key(
>> > + struct rhltable *hlt, const void *key, struct rhlist_head *list,
>> > + const struct rhashtable_params params)
>> > +{
>> > + return PTR_ERR(__rhashtable_insert_fast(&hlt->ht, key, &list->rhead,
>> > + params));
>> > +}
>> > +
>> > +static inline int rhltable_remove(
>> > + struct rhltable *hlt, struct rhlist_head *list,
>> > + const struct rhashtable_params params)
>> > +{
>> > + return rhashtable_remove_fast(&hlt->ht, &list->rhead, params);
>> > +}
>> > +
>> > +static inline void rhltable_free_and_destroy(struct rhltable *hlt,
>> > + void (*free_fn)(void *ptr,
>> > + void *arg),
>> > + void *arg)
>> > +{
>> > + return rhashtable_free_and_destroy(&hlt->ht, free_fn, arg);
>> > +}
>> > +
>> > +static inline void rhltable_destroy(struct rhltable *hlt)
>> > +{
>> > + return rhltable_free_and_destroy(hlt, NULL, NULL);
>> > +}
>> > +
>> > +static inline void rhltable_walk_enter(struct rhltable *hlt,
>> > + struct rhashtable_iter *iter)
>> > +{
>> > + rhashtable_walk_init(&hlt->ht, iter);
>> > +}
>> > +#endif /* !HAVE_RHLTABLE */
>> > +
>> > #ifndef HAVE_RHASHTABLE_LOOKUP_GET_INSERT_FAST
>> > /**
>> > * rhashtable_lookup_get_insert_fast - lookup and insert object into hash table
>> > diff --git a/lustre/include/lustre_export.h b/lustre/include/lustre_export.h
>> > index 5ead593..54887c9 100644
>> > --- a/lustre/include/lustre_export.h
>> > +++ b/lustre/include/lustre_export.h
>> > @@ -209,7 +209,7 @@ struct obd_export {
>> > /* Unlinked export list */
>> > struct list_head exp_stale_list;
>> > struct hlist_node exp_uuid_hash; /** uuid-export hash*/
>> > - struct hlist_node exp_nid_hash; /** nid-export hash */
>> > + struct rhlist_head exp_nid_hash; /** nid-export hash */
>> > struct hlist_node exp_gen_hash; /** last_rcvd clt gen hash */
>> > /**
>> > * All exports eligible for ping evictor are linked into a list
>> > diff --git a/lustre/include/obd.h b/lustre/include/obd.h
>> > index 1fcf0a2..8219710 100644
>> > --- a/lustre/include/obd.h
>> > +++ b/lustre/include/obd.h
>> > @@ -639,7 +639,7 @@ struct obd_device {
>> > /* uuid-export hash body */
>> > struct cfs_hash *obd_uuid_hash;
>> > /* nid-export hash body */
>> > - struct cfs_hash *obd_nid_hash;
>> > + struct rhltable obd_nid_hash;
>> > /* nid stats body */
>> > struct cfs_hash *obd_nid_stats_hash;
>> > /* client_generation-export hash body */
>> > @@ -750,6 +750,12 @@ struct obd_device {
>> > struct completion obd_kobj_unregister;
>> > };
>> >
>> > +int obd_nid_export_for_each(struct obd_device *obd, lnet_nid_t nid,
>> > + int cb(struct obd_export *exp, void *data),
>> > + void *data);
>> > +int obd_nid_add(struct obd_device *obd, struct obd_export *exp);
>> > +void obd_nid_del(struct obd_device *obd, struct obd_export *exp);
>> > +
>> > /* get/set_info keys */
>> > #define KEY_ASYNC "async"
>> > #define KEY_CHANGELOG_CLEAR "changelog_clear"
>> > diff --git a/lustre/include/obd_support.h b/lustre/include/obd_support.h
>> > index e9dd33e..0175cf8 100644
>> > --- a/lustre/include/obd_support.h
>> > +++ b/lustre/include/obd_support.h
>> > @@ -78,9 +78,6 @@ extern char obd_jobid_var[];
>> > #define HASH_UUID_BKT_BITS 5
>> > #define HASH_UUID_CUR_BITS 7
>> > #define HASH_UUID_MAX_BITS 12
>> > -#define HASH_NID_BKT_BITS 5
>> > -#define HASH_NID_CUR_BITS 7
>> > -#define HASH_NID_MAX_BITS 12
>> > #define HASH_NID_STATS_BKT_BITS 5
>> > #define HASH_NID_STATS_CUR_BITS 7
>> > #define HASH_NID_STATS_MAX_BITS 12
>> > diff --git a/lustre/ldlm/ldlm_flock.c b/lustre/ldlm/ldlm_flock.c
>> > index f848a36..4c1603a 100644
>> > --- a/lustre/ldlm/ldlm_flock.c
>> > +++ b/lustre/ldlm/ldlm_flock.c
>> > @@ -161,20 +161,18 @@ ldlm_flock_destroy(struct ldlm_lock *lock, enum ldlm_mode mode, __u64 flags)
>> > */
>> >
>> > struct ldlm_flock_lookup_cb_data {
>> > - __u64 *bl_owner;
>> > + u64 *bl_owner;
>>
>> Arrrggg. Please don't do this.
>>
>> > lock = cfs_hash_lookup(exp->exp_flock_hash, cb_data->bl_owner);
>> > - if (lock == NULL)
>> > + if (!lock)
>>
>> Or this.
>>
>> If you want to fix up this stuff, do it in a separate patch.
>> A patch should just do one thing.
>> I would actually prefer that the "add compatibilty code so we can use
>> rhltables in old kernels" was a separate patch from "use rhltables for
>> obd_nid_hash", but at least those two are conceptually related.
>>
>> It is much harder to read a patch if I keep having to say to myself "Oh,
>> that change is irrelevant here, I can ignore it".
>
> This is a pretty big patch for email review so I will break it up. I think
> it can be more than 2 and it doesn't matter for buildable from patch to
> patch since this us just for review.
I don't accept that there is a distinction between "For review" and "for
use". The patches as reviewed much be exactly the patches that get
applied.
It does take a little more work to make sure that you can build and test
after each patch, but it is only a little. Often the early patches
introduce functionality that is not immediately used, then the later
patches use it. Very rarely you might need to leave off a "static"
declaration, so the code will build even though the function isn't used.
Thanks,
NeilBrown
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