Re: [PATCH] block: Use non _rcu version of list functions for tag_set_list

[Jens Axboe]

On 7/28/20 7:29 AM, Daniel Wagner wrote:
> tag_set_list is only accessed under the tag_set_lock lock. There is
> no need for using the _rcu list functions.
> 
> The _rcu list function were introduced to allow read access to the
> tag_set_list protected under RCU, see 705cda97ee3a ("blk-mq: Make it
> safe to use RCU to iterate over blk_mq_tag_set.tag_list") and
> 05b79413946d ("Revert "blk-mq: don't handle TAG_SHARED in restart"").
> Those changes got reverted later but the cleanup commit missed a
> couple of places to undo the changes.

Applied, thanks.

-- 
Jens Axboe

Re: [PATCH] block: Use non _rcu version of list functions for tag_set_list

[Hannes Reinecke]

On 7/28/20 3:29 PM, Daniel Wagner wrote:

tag_set_list is only accessed under the tag_set_lock lock. There is
no need for using the _rcu list functions.

The _rcu list function were introduced to allow read access to the
tag_set_list protected under RCU, see 705cda97ee3a ("blk-mq: Make it
safe to use RCU to iterate over blk_mq_tag_set.tag_list") and
05b79413946d ("Revert "blk-mq: don't handle TAG_SHARED in restart"").
Those changes got reverted later but the cleanup commit missed a
couple of places to undo the changes.

Fixes: 97889f9ac24f ("blk-mq: remove synchronize_rcu() from 
blk_mq_del_queue_tag_set()"
Cc: Ming Lei 
Signed-off-by: Daniel Wagner 
---
  block/blk-mq.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e32cb0217135..14ee7506f32f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2792,7 +2792,7 @@ static void blk_mq_del_queue_tag_set(struct request_queue 
*q)
struct blk_mq_tag_set *set = q->tag_set;
  
  	mutex_lock(>tag_list_lock);

-   list_del_rcu(>tag_set_list);
+   list_del(>tag_set_list);
if (list_is_singular(>tag_list)) {
/* just transitioned to unshared */
set->flags &= ~BLK_MQ_F_TAG_SHARED;
@@ -2819,7 +2819,7 @@ static void blk_mq_add_queue_tag_set(struct 
blk_mq_tag_set *set,
}
if (set->flags & BLK_MQ_F_TAG_SHARED)
queue_set_hctx_shared(q, true);
-   list_add_tail_rcu(>tag_set_list, >tag_list);
+   list_add_tail(>tag_set_list, >tag_list);
  
  	mutex_unlock(>tag_list_lock);

  }


Indeed.

Reviewed-by: Hannes Reinecke 

Cheers,

Hannes
--
Dr. Hannes ReineckeTeamlead Storage & Networking
h...@suse.de   +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

[PATCH] block: Use non _rcu version of list functions for tag_set_list

[Daniel Wagner]

tag_set_list is only accessed under the tag_set_lock lock. There is
no need for using the _rcu list functions.

The _rcu list function were introduced to allow read access to the
tag_set_list protected under RCU, see 705cda97ee3a ("blk-mq: Make it
safe to use RCU to iterate over blk_mq_tag_set.tag_list") and
05b79413946d ("Revert "blk-mq: don't handle TAG_SHARED in restart"").
Those changes got reverted later but the cleanup commit missed a
couple of places to undo the changes.

Fixes: 97889f9ac24f ("blk-mq: remove synchronize_rcu() from 
blk_mq_del_queue_tag_set()"
Cc: Ming Lei 
Signed-off-by: Daniel Wagner 
---
 block/blk-mq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e32cb0217135..14ee7506f32f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2792,7 +2792,7 @@ static void blk_mq_del_queue_tag_set(struct request_queue 
*q)
struct blk_mq_tag_set *set = q->tag_set;
 
mutex_lock(>tag_list_lock);
-   list_del_rcu(>tag_set_list);
+   list_del(>tag_set_list);
if (list_is_singular(>tag_list)) {
/* just transitioned to unshared */
set->flags &= ~BLK_MQ_F_TAG_SHARED;
@@ -2819,7 +2819,7 @@ static void blk_mq_add_queue_tag_set(struct 
blk_mq_tag_set *set,
}
if (set->flags & BLK_MQ_F_TAG_SHARED)
queue_set_hctx_shared(q, true);
-   list_add_tail_rcu(>tag_set_list, >tag_list);
+   list_add_tail(>tag_set_list, >tag_list);
 
mutex_unlock(>tag_list_lock);
 }
-- 
2.16.4