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Commit bab8b4cc authored by NeilBrown's avatar NeilBrown Committed by Greg Kroah-Hartman
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staging: lustre: lu_object: move retry logic inside htable_lookup 



The current retry logic, to wait when a 'dying' object is found,
spans multiple functions.  The process is attached to a waitqueue
and set TASK_UNINTERRUPTIBLE in htable_lookup, and this status
is passed back through lu_object_find_try() to lu_object_find_at()
where schedule() is called and the process is removed from the queue.

This can be simplified by moving all the logic (including
hashtable locking) inside htable_lookup(), which now never returns
EAGAIN.

Note that htable_lookup() is called with the hash bucket lock
held, and will drop and retake it if it needs to schedule.

I made this a 'goto' loop rather than a 'while(1)' loop as the
diff is easier to read.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e167b370

drivers/staging/lustre/lustre/obdclass/lu_object.c

+27 −43
Original line number Diff line number Diff line
@@ -584,16 +584,24 @@ void lu_object_print(const struct lu_env *env, void *cookie, 
}

EXPORT_SYMBOL(lu_object_print);



/*

 * NOTE: htable_lookup() is called with the relevant

 * hash bucket locked, but might drop and re-acquire the lock.

 */

static struct lu_object *htable_lookup(struct lu_site *s,

				       struct cfs_hash_bd *bd,

				       const struct lu_fid *f,

				       wait_queue_entry_t *waiter,

				       __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 = cfs_hash_bd_version_get(bd);

	__u64 ver;

	wait_queue_entry_t waiter;



retry:

	ver = cfs_hash_bd_version_get(bd);



	if (*version == ver)

		return ERR_PTR(-ENOENT);
@@ -626,11 +634,15 @@ static struct lu_object *htable_lookup(struct lu_site *s, 
	 * drained), and moreover, lookup has to wait until object is freed.

	 */



	init_waitqueue_entry(waiter, current);

	add_wait_queue(&bkt->lsb_marche_funebre, waiter);

	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);

	return ERR_PTR(-EAGAIN);

	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;

}



/**
@@ -694,13 +706,14 @@ static struct lu_object *lu_object_new(const struct lu_env *env, 
}



/**

 * 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.

 */

static struct lu_object *lu_object_find_try(const struct lu_env *env,

struct lu_object *lu_object_find_at(const struct lu_env *env,

				    struct lu_device *dev,

				    const struct lu_fid *f,

					    const struct lu_object_conf *conf,

					    wait_queue_entry_t *waiter)

				    const struct lu_object_conf *conf)

{

	struct lu_object      *o;

	struct lu_object      *shadow;
@@ -726,8 +739,6 @@ static struct lu_object *lu_object_find_try(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).

	 */

	if (conf && conf->loc_flags & LOC_F_NEW)

		return lu_object_new(env, dev, f, conf);
@@ -735,8 +746,9 @@ static struct lu_object *lu_object_find_try(const struct lu_env *env, 
	s  = dev->ld_site;

	hs = s->ls_obj_hash;

	cfs_hash_bd_get_and_lock(hs, (void *)f, &bd, 1);

	o = htable_lookup(s, &bd, f, waiter, &version);

	o = htable_lookup(s, &bd, f, &version);

	cfs_hash_bd_unlock(hs, &bd, 1);



	if (!IS_ERR(o) || PTR_ERR(o) != -ENOENT)

		return o;
@@ -752,7 +764,7 @@ static struct lu_object *lu_object_find_try(const struct lu_env *env, 


	cfs_hash_bd_lock(hs, &bd, 1);



	shadow = htable_lookup(s, &bd, f, waiter, &version);

	shadow = htable_lookup(s, &bd, f, &version);

	if (likely(PTR_ERR(shadow) == -ENOENT)) {

		cfs_hash_bd_add_locked(hs, &bd, &o->lo_header->loh_hash);

		cfs_hash_bd_unlock(hs, &bd, 1);
@@ -767,34 +779,6 @@ static struct lu_object *lu_object_find_try(const struct lu_env *env, 
	lu_object_free(env, o);

	return shadow;

}



/**

 * 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.

 */

struct lu_object *lu_object_find_at(const struct lu_env *env,

				    struct lu_device *dev,

				    const struct lu_fid *f,

				    const struct lu_object_conf *conf)

{

	wait_queue_head_t	*wq;

	struct lu_object	*obj;

	wait_queue_entry_t	   wait;



	while (1) {

		obj = lu_object_find_try(env, dev, f, conf, &wait);

		if (obj != ERR_PTR(-EAGAIN))

			return obj;

		/*

		 * lu_object_find_try() already added waiter into the

		 * wait queue.

		 */

		schedule();

		wq = lu_site_wq_from_fid(dev->ld_site, (void *)f);

		remove_wait_queue(wq, &wait);

	}

}

EXPORT_SYMBOL(lu_object_find_at);



/**