On Mon, May 14 2018, James Simmons wrote: > From: Lai Siyao <lai.si...@intel.com> > > 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.si...@intel.com> > Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9049 > Reviewed-on: https://review.whamcloud.com/26965 > Reviewed-by: Alex Zhuravlev <alexey.zhurav...@intel.com> > Tested-by: Cliff White <cliff.wh...@intel.com> > Reviewed-by: Fan Yong <fan.y...@intel.com> > Reviewed-by: Oleg Drokin <oleg.dro...@intel.com> > Signed-off-by: James Simmons <jsimm...@infradead.org>
Reviewed-by: NeilBrown <ne...@suse.com>
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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