> On Wed, May 02 2018, James Simmons wrote: > > > From: Lai Siyao <lai.siyao@xxxxxxxxx> > > > > Currently we set LU_OBJECT_HEARD_BANSHEE on object when we want > > to remove object from cache, but this may lead to deadlock, because > > when other process lookup such object, it needs to wait for this > > object until release (done at last refcount put), while that process > > maybe already hold an LDLM lock. > > > > Now that current code can handle dying object correctly, we can just > > return such object in lookup, thus the above deadlock can be avoided. > > I think one of the reasons that I didn't apply this to mainline myself > is that "Now that" comment. When is the "now" that it is referring to? > Are were sure that all code in mainline "can handle dying objects > correctly"?? So I talked to Lai and he posted the LU-9049 ticket what patches need to land before this one. Only one patch is of concern and its for LU-9203 which doesn't apply to the staging tree since we don't have the LNet SMP updates in our tree. I saved notes about making sure LU-9203 lands together with the future LNet SMP changes. As it stands it is safe to land to staging. > > Signed-off-by: Lai Siyao <lai.siyao@xxxxxxxxx> > > Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9049 > > Reviewed-on: https://review.whamcloud.com/26965 > > Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@xxxxxxxxx> > > Tested-by: Cliff White <cliff.white@xxxxxxxxx> > > Reviewed-by: Fan Yong <fan.yong@xxxxxxxxx> > > Reviewed-by: Oleg Drokin <oleg.drokin@xxxxxxxxx> > > Signed-off-by: James Simmons <jsimmons@xxxxxxxxxxxxx> > > --- > > drivers/staging/lustre/lustre/include/lu_object.h | 2 +- > > drivers/staging/lustre/lustre/obdclass/lu_object.c | 82 +++++++++------------- > > 2 files changed, 36 insertions(+), 48 deletions(-) > > > > diff --git a/drivers/staging/lustre/lustre/include/lu_object.h b/drivers/staging/lustre/lustre/include/lu_object.h > > index f29bbca..232063a 100644 > > --- a/drivers/staging/lustre/lustre/include/lu_object.h > > +++ b/drivers/staging/lustre/lustre/include/lu_object.h > > @@ -673,7 +673,7 @@ static inline void lu_object_get(struct lu_object *o) > > } > > > > /** > > - * Return true of object will not be cached after last reference to it is > > + * Return true if object will not be cached after last reference to it is > > * released. > > */ > > static inline int lu_object_is_dying(const struct lu_object_header *h) > > diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c > > index 8b507f1..9311703 100644 > > --- a/drivers/staging/lustre/lustre/obdclass/lu_object.c > > +++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c > > @@ -589,19 +589,13 @@ static struct lu_object *htable_lookup(struct lu_site *s, > > const struct lu_fid *f, > > __u64 *version) > > { > > - struct cfs_hash *hs = s->ls_obj_hash; > > struct lu_site_bkt_data *bkt; > > struct lu_object_header *h; > > struct hlist_node *hnode; > > - __u64 ver; > > - wait_queue_entry_t waiter; > > + u64 ver = cfs_hash_bd_version_get(bd); > > > > -retry: > > - ver = cfs_hash_bd_version_get(bd); > > - > > - if (*version == ver) { > > + if (*version == ver) > > return ERR_PTR(-ENOENT); > > - } > > > > *version = ver; > > bkt = cfs_hash_bd_extra_get(s->ls_obj_hash, bd); > > @@ -615,31 +609,13 @@ static struct lu_object *htable_lookup(struct lu_site *s, > > } > > > > h = container_of(hnode, struct lu_object_header, loh_hash); > > - if (likely(!lu_object_is_dying(h))) { > > - cfs_hash_get(s->ls_obj_hash, hnode); > > - lprocfs_counter_incr(s->ls_stats, LU_SS_CACHE_HIT); > > - if (!list_empty(&h->loh_lru)) { > > - list_del_init(&h->loh_lru); > > - percpu_counter_dec(&s->ls_lru_len_counter); > > - } > > - return lu_object_top(h); > > + cfs_hash_get(s->ls_obj_hash, hnode); > > + lprocfs_counter_incr(s->ls_stats, LU_SS_CACHE_HIT); > > + if (!list_empty(&h->loh_lru)) { > > + list_del_init(&h->loh_lru); > > + percpu_counter_dec(&s->ls_lru_len_counter); > > } > > - > > - /* > > - * Lookup found an object being destroyed this object cannot be > > - * returned (to assure that references to dying objects are eventually > > - * drained), and moreover, lookup has to wait until object is freed. > > - */ > > - > > - init_waitqueue_entry(&waiter, current); > > - add_wait_queue(&bkt->lsb_marche_funebre, &waiter); > > - set_current_state(TASK_UNINTERRUPTIBLE); > > - lprocfs_counter_incr(s->ls_stats, LU_SS_CACHE_DEATH_RACE); > > - cfs_hash_bd_unlock(hs, bd, 1); > > - schedule(); > > - remove_wait_queue(&bkt->lsb_marche_funebre, &waiter); > > - cfs_hash_bd_lock(hs, bd, 1); > > - goto retry; > > + return lu_object_top(h); > > } > > > > /** > > @@ -680,6 +656,8 @@ static void lu_object_limit(const struct lu_env *env, struct lu_device *dev) > > } > > > > /** > > + * Core logic of lu_object_find*() functions. > > + * > > * Much like lu_object_find(), but top level device of object is specifically > > * \a dev rather than top level device of the site. This interface allows > > * objects of different "stacking" to be created within the same site. > > @@ -713,36 +691,46 @@ struct lu_object *lu_object_find_at(const struct lu_env *env, > > * It is unnecessary to perform lookup-alloc-lookup-insert, instead, > > * just alloc and insert directly. > > * > > + * If dying object is found during index search, add @waiter to the > > + * site wait-queue and return ERR_PTR(-EAGAIN). > > It seems odd to add this comment here, when it seems to describe code > that is being removed. > I can see that this comment is added by the upstream patch > Commit: fa14bdf6b648 ("LU-9049 obdclass: change object lookup to no wait mode") > but I cannot see what it refers to. > > Otherwise that patch looks good. > > Thanks, > NeilBrown > _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
