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Message-ID: <152565448811.30131.18427155547615728371.stgit@noble>
Date: Mon, 07 May 2018 10:54:48 +1000
From: NeilBrown <neilb@...e.com>
To: Oleg Drokin <oleg.drokin@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
James Simmons <jsimmons@...radead.org>,
Andreas Dilger <andreas.dilger@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: [PATCH 04/10] 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: NeilBrown <neilb@...e.com>
---
drivers/staging/lustre/lustre/obdclass/lu_object.c | 70 ++++++++------------
1 file changed, 27 insertions(+), 43 deletions(-)
diff --git a/drivers/staging/lustre/lustre/obdclass/lu_object.c b/drivers/staging/lustre/lustre/obdclass/lu_object.c
index bf5b309edeae..0c9419a6d5d6 100644
--- a/drivers/staging/lustre/lustre/obdclass/lu_object.c
+++ b/drivers/staging/lustre/lustre/obdclass/lu_object.c
@@ -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_device *dev,
- const struct lu_fid *f,
- const struct lu_object_conf *conf,
- wait_queue_entry_t *waiter)
+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)
{
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);
/**
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