* [PATCH V2] block: release disk reference in hd_struct_free_work
@ 2020-09-01 10:07 Ming Lei
2020-09-01 10:09 ` Christoph Hellwig
2020-09-01 14:34 ` Jens Axboe
0 siblings, 2 replies; 3+ messages in thread
From: Ming Lei @ 2020-09-01 10:07 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-block, Ming Lei, Ilya Dryomov, Luis Chamberlain,
Christoph Hellwig, Bart Van Assche
Commit e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal")
stops to release request queue from wq context because that commit
supposed all blk_put_queue() is called in context which is allowed
to sleep. However, this assumption isn't true because we release disk's
reference in partition's percpu_ref's ->release() which doesn't allow
to sleep, because the ->release() is run via call_rcu().
Fixes this issue by moving put disk reference into hd_struct_free_work()
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Fixes: e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal")
Reported-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Ilya Dryomov <idryomov@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
---
V2:
- take Christoph's comment
block/partitions/core.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/block/partitions/core.c b/block/partitions/core.c
index e62a98a8eeb7..5a18c8edabbc 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -278,6 +278,15 @@ static void hd_struct_free_work(struct work_struct *work)
{
struct hd_struct *part =
container_of(to_rcu_work(work), struct hd_struct, rcu_work);
+ struct gendisk *disk = part_to_disk(part);
+
+ /*
+ * Release the disk reference acquired in delete_partition here.
+ * We can't release it in hd_struct_free because the final put_device
+ * needs process context and thus can't be run directly from a
+ * percpu_ref ->release handler.
+ */
+ put_device(disk_to_dev(disk));
part->start_sect = 0;
part->nr_sects = 0;
@@ -293,7 +302,6 @@ static void hd_struct_free(struct percpu_ref *ref)
rcu_dereference_protected(disk->part_tbl, 1);
rcu_assign_pointer(ptbl->last_lookup, NULL);
- put_device(disk_to_dev(disk));
INIT_RCU_WORK(&part->rcu_work, hd_struct_free_work);
queue_rcu_work(system_wq, &part->rcu_work);
--
2.25.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V2] block: release disk reference in hd_struct_free_work
2020-09-01 10:07 [PATCH V2] block: release disk reference in hd_struct_free_work Ming Lei
@ 2020-09-01 10:09 ` Christoph Hellwig
2020-09-01 14:34 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Christoph Hellwig @ 2020-09-01 10:09 UTC (permalink / raw)
To: Ming Lei
Cc: Jens Axboe, linux-block, Ilya Dryomov, Luis Chamberlain,
Christoph Hellwig, Bart Van Assche
On Tue, Sep 01, 2020 at 06:07:38PM +0800, Ming Lei wrote:
> Commit e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal")
> stops to release request queue from wq context because that commit
> supposed all blk_put_queue() is called in context which is allowed
> to sleep. However, this assumption isn't true because we release disk's
> reference in partition's percpu_ref's ->release() which doesn't allow
> to sleep, because the ->release() is run via call_rcu().
>
> Fixes this issue by moving put disk reference into hd_struct_free_work()
>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> Fixes: e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal")
> Reported-by: Ilya Dryomov <idryomov@gmail.com>
> Tested-by: Ilya Dryomov <idryomov@gmail.com>
> Cc: Luis Chamberlain <mcgrof@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Bart Van Assche <bvanassche@acm.org>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH V2] block: release disk reference in hd_struct_free_work
2020-09-01 10:07 [PATCH V2] block: release disk reference in hd_struct_free_work Ming Lei
2020-09-01 10:09 ` Christoph Hellwig
@ 2020-09-01 14:34 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Jens Axboe @ 2020-09-01 14:34 UTC (permalink / raw)
To: Ming Lei
Cc: linux-block, Ilya Dryomov, Luis Chamberlain, Christoph Hellwig,
Bart Van Assche
On 9/1/20 4:07 AM, Ming Lei wrote:
> Commit e8c7d14ac6c3 ("block: revert back to synchronous request_queue removal")
> stops to release request queue from wq context because that commit
> supposed all blk_put_queue() is called in context which is allowed
> to sleep. However, this assumption isn't true because we release disk's
> reference in partition's percpu_ref's ->release() which doesn't allow
> to sleep, because the ->release() is run via call_rcu().
>
> Fixes this issue by moving put disk reference into hd_struct_free_work()
Applied, thanks Ming.
--
Jens Axboe
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-09-01 14:34 UTC | newest]
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2020-09-01 10:07 [PATCH V2] block: release disk reference in hd_struct_free_work Ming Lei
2020-09-01 10:09 ` Christoph Hellwig
2020-09-01 14:34 ` Jens Axboe
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