On Mon, May 14 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. > > 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> Reviewed-by: NeilBrown <neilb@xxxxxxxx> Thanks :-) NeilBrown > --- > Changelog: > > v1) Initial patch that didn't apply to staging-testing branch > v2) Rebased after Neil's patches landed. Remove unlikely() test > as requested by Dan Carpenter > > drivers/staging/lustre/lustre/obdclass/lu_object.c | 39 +++++----------------- > 1 file changed, 9 insertions(+), 30 deletions(-) > > diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c > index f14e350..e0abd4f 100644 > --- a/drivers/staging/lustre/lustre/obdclass/lu_object.c > +++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c > @@ -593,15 +593,10 @@ 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; > - > -retry: > - ver = cfs_hash_bd_version_get(bd); > + u64 ver = cfs_hash_bd_version_get(bd); > > if (*version == ver) > return ERR_PTR(-ENOENT); > @@ -618,31 +613,13 @@ 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); > } > > /** > @@ -683,6 +660,8 @@ 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. > -- > 1.8.3.1
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