Re: [PATCH 5/8] blk-mq: make blk_abort_request() trigger timeout path

[t...@kernel.org]

On Mon, Jan 08, 2018 at 10:10:01PM +, Bart Van Assche wrote:
> Other req->deadline writes are protected by preempt_disable(),
> write_seqcount_begin(>gstate_seq), write_seqcount_end(>gstate_seq)
> and preempt_enable(). I think it's fine that the above req->deadline store
> does not have that protection but I also think that that deserves a comment.

Will add.

Thanks.

-- 
tejun

Re: [PATCH 5/8] blk-mq: make blk_abort_request() trigger timeout path

[Bart Van Assche]

On Mon, 2018-01-08 at 11:15 -0800, Tejun Heo wrote:
> @@ -156,12 +156,12 @@ void blk_timeout_work(struct work_struct *work)
>   */
>  void blk_abort_request(struct request *req)
>  {
> - if (blk_mark_rq_complete(req))
> - return;
> -
>   if (req->q->mq_ops) {
> - blk_mq_rq_timed_out(req, false);
> + req->deadline = jiffies;
> + mod_timer(>q->timeout, 0);
>   } else {
> + if (blk_mark_rq_complete(req))
> + return;
>   blk_delete_timer(req);
>   blk_rq_timed_out(req);
>   }

Other req->deadline writes are protected by preempt_disable(),
write_seqcount_begin(>gstate_seq), write_seqcount_end(>gstate_seq)
and preempt_enable(). I think it's fine that the above req->deadline store
does not have that protection but I also think that that deserves a comment.

Thanks,

Bart.

[PATCH 5/8] blk-mq: make blk_abort_request() trigger timeout path

[Tejun Heo]

With issue/complete and timeout paths now using the generation number
and state based synchronization, blk_abort_request() is the only one
which depends on REQ_ATOM_COMPLETE for arbitrating completion.

There's no reason for blk_abort_request() to be a completely separate
path.  This patch makes blk_abort_request() piggyback on the timeout
path instead of trying to terminate the request directly.

This removes the last dependency on REQ_ATOM_COMPLETE in blk-mq.

Note that this makes blk_abort_request() asynchronous - it initiates
abortion but the actual termination will happen after a short while,
even when the caller owns the request.  AFAICS, SCSI and ATA should be
fine with that and I think mtip32xx and dasd should be safe but not
completely sure.  It'd be great if people who know the drivers take a
look.

Signed-off-by: Tejun Heo 
Cc: Asai Thambi SP 
Cc: Stefan Haberland 
Cc: Jan Hoeppner 
---
 block/blk-mq.c  | 2 +-
 block/blk-mq.h  | 2 --
 block/blk-timeout.c | 8 
 3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 41bfd27..bed4cb8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -814,7 +814,7 @@ struct blk_mq_timeout_data {
unsigned int nr_expired;
 };
 
-void blk_mq_rq_timed_out(struct request *req, bool reserved)
+static void blk_mq_rq_timed_out(struct request *req, bool reserved)
 {
const struct blk_mq_ops *ops = req->q->mq_ops;
enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index cf01f6f..6b2d616 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -94,8 +94,6 @@ extern int blk_mq_sysfs_register(struct request_queue *q);
 extern void blk_mq_sysfs_unregister(struct request_queue *q);
 extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
 
-extern void blk_mq_rq_timed_out(struct request *req, bool reserved);
-
 void blk_mq_release(struct request_queue *q);
 
 /**
diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index 6427be7..d580af3 100644
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -156,12 +156,12 @@ void blk_timeout_work(struct work_struct *work)
  */
 void blk_abort_request(struct request *req)
 {
-   if (blk_mark_rq_complete(req))
-   return;
-
if (req->q->mq_ops) {
-   blk_mq_rq_timed_out(req, false);
+   req->deadline = jiffies;
+   mod_timer(>q->timeout, 0);
} else {
+   if (blk_mark_rq_complete(req))
+   return;
blk_delete_timer(req);
blk_rq_timed_out(req);
}
-- 
2.9.5