[PATCH 0/7] Improve I/O priority handling

[PATCH 0/7] Improve I/O priority handling

[Damien Le Moal]

This small series based on for-4.21/block brings improvements to I/O priority
hanlding. The main fixes are in patches 5, 6 and 7. These fix BIO and request
I/O priority initialization for both the synchronous and asynchronous pathes.

Of note is that patch 3 is what I beleive a clear bug fix but can result in
userland applications behavior change since a different I/O priority values
will be returned for processes that have *not* executed ioprio_set(). This
needs careful review.

Damien Le Moal (7):
  aio: Comment use of IOCB_FLAG_IOPRIO aio flag
  block: Remove bio->bi_ioc
  block: Fix get_task_ioprio() default return value
  block: Introduce get_current_ioprio()
  aio: Fix fallback I/O priority value
  block: prevent merging of requests with different priorities
  block: Initialize BIO I/O priority early

 block/bio.c                  |  4 ----
 block/blk-core.c             | 12 +-----------
 block/blk-merge.c            | 14 ++++++++++++--
 block/blk-mq-sched.c         |  4 ++--
 block/blk-mq-sched.h         |  2 +-
 block/blk-mq.c               |  4 ++--
 block/blk.h                  | 16 ----------------
 block/ioprio.c               |  2 +-
 fs/aio.c                     |  2 +-
 include/linux/blk_types.h    |  3 +--
 include/linux/fs.h           |  2 +-
 include/linux/ioprio.h       | 13 +++++++++++++
 include/uapi/linux/aio_abi.h |  2 ++
 13 files changed, 37 insertions(+), 43 deletions(-)

-- 
2.19.1

[PATCH 1/7] aio: Comment use of IOCB_FLAG_IOPRIO aio flag

[Damien Le Moal]

Comment the use of the IOCB_FLAG_IOPRIO aio flag similarly to the
IOCB_FLAG_RESFD flag.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 include/uapi/linux/aio_abi.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index ce43d340f010..8387e0af0f76 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -50,6 +50,8 @@ enum {
  *
  * IOCB_FLAG_RESFD - Set if the "aio_resfd" member of the "struct iocb"
  *                   is valid.
+ * IOCB_FLAG_IOPRIO - Set if the "aio_reqprio" member of the "struct iocb"
+ *                    is valid.
  */
 #define IOCB_FLAG_RESFD		(1 << 0)
 #define IOCB_FLAG_IOPRIO	(1 << 1)
-- 
2.19.1

Re: [PATCH 1/7] aio: Comment use of IOCB_FLAG_IOPRIO aio flag

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:25PM +0900, Damien Le Moal wrote:
> Comment the use of the IOCB_FLAG_IOPRIO aio flag similarly to the
> IOCB_FLAG_RESFD flag.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 1/7] aio: Comment use of IOCB_FLAG_IOPRIO aio flag

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

-- 
Johannes Thumshirn                                        SUSE Labs
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

[PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

bio->bi_ioc is never set so always NULL. Remove references to it in
bio_disassociate_task() and in rq_ioc() and delete this field from
struct bio. With this change, rq_ioc() always returns
current->io_context without the need for a bio argument. Further
simplify the code and make it more readable by also removing this
helper, which also allows to simplify blk_mq_sched_assign_ioc() by
removing its bio argument.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/bio.c               |  4 ----
 block/blk-core.c          |  2 +-
 block/blk-mq-sched.c      |  4 ++--
 block/blk-mq-sched.h      |  2 +-
 block/blk-mq.c            |  4 ++--
 block/blk.h               | 16 ----------------
 include/linux/blk_types.h |  3 +--
 7 files changed, 7 insertions(+), 28 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 4f4d9884443b..03895cc0d74a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
  */
 void bio_disassociate_task(struct bio *bio)
 {
-	if (bio->bi_ioc) {
-		put_io_context(bio->bi_ioc);
-		bio->bi_ioc = NULL;
-	}
 	if (bio->bi_css) {
 		css_put(bio->bi_css);
 		bio->bi_css = NULL;
diff --git a/block/blk-core.c b/block/blk-core.c
index d6e8ab9ca99d..492648c96992 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
 
 void blk_init_request_from_bio(struct request *req, struct bio *bio)
 {
-	struct io_context *ioc = rq_ioc(bio);
+	struct io_context *ioc = current->io_context;
 
 	if (bio->bi_opf & REQ_RAHEAD)
 		req->cmd_flags |= REQ_FAILFAST_MASK;
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index d084f731d104..13b8dc332541 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,
 }
 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
 
-void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
+void blk_mq_sched_assign_ioc(struct request *rq)
 {
 	struct request_queue *q = rq->q;
-	struct io_context *ioc = rq_ioc(bio);
+	struct io_context *ioc = current->io_context;
 	struct io_cq *icq;
 
 	spin_lock_irq(&q->queue_lock);
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 7ff5671bf128..0f719c8532ae 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -8,7 +8,7 @@
 void blk_mq_sched_free_hctx_data(struct request_queue *q,
 				 void (*exit)(struct blk_mq_hw_ctx *));
 
-void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
+void blk_mq_sched_assign_ioc(struct request *rq);
 
 void blk_mq_sched_request_inserted(struct request *rq);
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 32b246ed44c0..636f80b96fa6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
 	if (!op_is_flush(data->cmd_flags)) {
 		rq->elv.icq = NULL;
 		if (e && e->type->ops.prepare_request) {
-			if (e->type->icq_cache && rq_ioc(bio))
-				blk_mq_sched_assign_ioc(rq, bio);
+			if (e->type->icq_cache)
+				blk_mq_sched_assign_ioc(rq);
 
 			e->type->ops.prepare_request(rq, bio);
 			rq->rq_flags |= RQF_ELVPRIV;
diff --git a/block/blk.h b/block/blk.h
index 816a9abb87cd..610948157a5b 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
 
 int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
 
-/**
- * rq_ioc - determine io_context for request allocation
- * @bio: request being allocated is for this bio (can be %NULL)
- *
- * Determine io_context to use for request allocation for @bio.  May return
- * %NULL if %current->io_context doesn't exist.
- */
-static inline struct io_context *rq_ioc(struct bio *bio)
-{
-#ifdef CONFIG_BLK_CGROUP
-	if (bio && bio->bi_ioc)
-		return bio->bi_ioc;
-#endif
-	return current->io_context;
-}
-
 /**
  * create_io_context - try to create task->io_context
  * @gfp_mask: allocation mask
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dbdbfbd6a987..c0ba1a038ff3 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -174,10 +174,9 @@ struct bio {
 	void			*bi_private;
 #ifdef CONFIG_BLK_CGROUP
 	/*
-	 * Optional ioc and css associated with this bio.  Put on bio
+	 * Optional css associated with this bio.  Put on bio
 	 * release.  Read comment on top of bio_associate_current().
 	 */
-	struct io_context	*bi_ioc;
 	struct cgroup_subsys_state *bi_css;
 	struct blkcg_gq		*bi_blkg;
 	struct bio_issue	bi_issue;
-- 
2.19.1

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:26PM +0900, Damien Le Moal wrote:
> bio->bi_ioc is never set so always NULL. Remove references to it in
> bio_disassociate_task() and in rq_ioc() and delete this field from
> struct bio. With this change, rq_ioc() always returns
> current->io_context without the need for a bio argument. Further
> simplify the code and make it more readable by also removing this
> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
> removing its bio argument.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

-- 
Johannes Thumshirn                                        SUSE Labs
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Adam Manzanares]

On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote:
> bio->bi_ioc is never set so always NULL. Remove references to it in
> bio_disassociate_task() and in rq_ioc() and delete this field from
> struct bio. With this change, rq_ioc() always returns
> current->io_context without the need for a bio argument. Further
> simplify the code and make it more readable by also removing this
> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
> removing its bio argument.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>


Reviewed by: 
> ---
>  block/bio.c               |  4 ----
>  block/blk-core.c          |  2 +-
>  block/blk-mq-sched.c      |  4 ++--
>  block/blk-mq-sched.h      |  2 +-
>  block/blk-mq.c            |  4 ++--
>  block/blk.h               | 16 ----------------
>  include/linux/blk_types.h |  3 +--
>  7 files changed, 7 insertions(+), 28 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 4f4d9884443b..03895cc0d74a 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct
> blkcg_gq *blkg)
>   */
>  void bio_disassociate_task(struct bio *bio)
>  {
> -	if (bio->bi_ioc) {
> -		put_io_context(bio->bi_ioc);
> -		bio->bi_ioc = NULL;
> -	}
>  	if (bio->bi_css) {
>  		css_put(bio->bi_css);
>  		bio->bi_css = NULL;
> diff --git a/block/blk-core.c b/block/blk-core.c
> index d6e8ab9ca99d..492648c96992 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct
> request_queue *q)
>  
>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
>  {
> -	struct io_context *ioc = rq_ioc(bio);
> +	struct io_context *ioc = current->io_context;
>  
>  	if (bio->bi_opf & REQ_RAHEAD)
>  		req->cmd_flags |= REQ_FAILFAST_MASK;
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index d084f731d104..13b8dc332541 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct
> request_queue *q,
>  }
>  EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>  
> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
> +void blk_mq_sched_assign_ioc(struct request *rq)
>  {
>  	struct request_queue *q = rq->q;
> -	struct io_context *ioc = rq_ioc(bio);
> +	struct io_context *ioc = current->io_context;
>  	struct io_cq *icq;
>  
>  	spin_lock_irq(&q->queue_lock);
> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
> index 7ff5671bf128..0f719c8532ae 100644
> --- a/block/blk-mq-sched.h
> +++ b/block/blk-mq-sched.h
> @@ -8,7 +8,7 @@
>  void blk_mq_sched_free_hctx_data(struct request_queue *q,
>  				 void (*exit)(struct blk_mq_hw_ctx *));
>  
> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
> +void blk_mq_sched_assign_ioc(struct request *rq);
>  
>  void blk_mq_sched_request_inserted(struct request *rq);
>  bool blk_mq_sched_try_merge(struct request_queue *q, struct bio
> *bio,
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 32b246ed44c0..636f80b96fa6 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct
> request_queue *q,
>  	if (!op_is_flush(data->cmd_flags)) {
>  		rq->elv.icq = NULL;
>  		if (e && e->type->ops.prepare_request) {
> -			if (e->type->icq_cache && rq_ioc(bio))
> -				blk_mq_sched_assign_ioc(rq, bio);
> +			if (e->type->icq_cache)
> +				blk_mq_sched_assign_ioc(rq);
>  
>  			e->type->ops.prepare_request(rq, bio);
>  			rq->rq_flags |= RQF_ELVPRIV;
> diff --git a/block/blk.h b/block/blk.h
> index 816a9abb87cd..610948157a5b 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
>  
>  int create_task_io_context(struct task_struct *task, gfp_t gfp_mask,
> int node);
>  
> -/**
> - * rq_ioc - determine io_context for request allocation
> - * @bio: request being allocated is for this bio (can be %NULL)
> - *
> - * Determine io_context to use for request allocation for @bio.  May
> return
> - * %NULL if %current->io_context doesn't exist.
> - */
> -static inline struct io_context *rq_ioc(struct bio *bio)
> -{
> -#ifdef CONFIG_BLK_CGROUP
> -	if (bio && bio->bi_ioc)
> -		return bio->bi_ioc;
> -#endif
> -	return current->io_context;
> -}
> -
>  /**
>   * create_io_context - try to create task->io_context
>   * @gfp_mask: allocation mask
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index dbdbfbd6a987..c0ba1a038ff3 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -174,10 +174,9 @@ struct bio {
>  	void			*bi_private;
>  #ifdef CONFIG_BLK_CGROUP
>  	/*
> -	 * Optional ioc and css associated with this bio.  Put on bio
> +	 * Optional css associated with this bio.  Put on bio
>  	 * release.  Read comment on top of bio_associate_current().
>  	 */
> -	struct io_context	*bi_ioc;
>  	struct cgroup_subsys_state *bi_css;
>  	struct blkcg_gq		*bi_blkg;
>  	struct bio_issue	bi_issue;

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Ming Lei]

On Mon, Nov 19, 2018 at 12:51:26PM +0900, Damien Le Moal wrote:
> bio->bi_ioc is never set so always NULL. Remove references to it in
> bio_disassociate_task() and in rq_ioc() and delete this field from
> struct bio. With this change, rq_ioc() always returns
> current->io_context without the need for a bio argument. Further
> simplify the code and make it more readable by also removing this
> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
> removing its bio argument.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>  block/bio.c               |  4 ----
>  block/blk-core.c          |  2 +-
>  block/blk-mq-sched.c      |  4 ++--
>  block/blk-mq-sched.h      |  2 +-
>  block/blk-mq.c            |  4 ++--
>  block/blk.h               | 16 ----------------
>  include/linux/blk_types.h |  3 +--
>  7 files changed, 7 insertions(+), 28 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 4f4d9884443b..03895cc0d74a 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
>   */
>  void bio_disassociate_task(struct bio *bio)
>  {
> -	if (bio->bi_ioc) {
> -		put_io_context(bio->bi_ioc);
> -		bio->bi_ioc = NULL;
> -	}
>  	if (bio->bi_css) {
>  		css_put(bio->bi_css);
>  		bio->bi_css = NULL;
> diff --git a/block/blk-core.c b/block/blk-core.c
> index d6e8ab9ca99d..492648c96992 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
>  
>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
>  {
> -	struct io_context *ioc = rq_ioc(bio);
> +	struct io_context *ioc = current->io_context;
>  
>  	if (bio->bi_opf & REQ_RAHEAD)
>  		req->cmd_flags |= REQ_FAILFAST_MASK;
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index d084f731d104..13b8dc332541 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,
>  }
>  EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>  
> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
> +void blk_mq_sched_assign_ioc(struct request *rq)
>  {
>  	struct request_queue *q = rq->q;
> -	struct io_context *ioc = rq_ioc(bio);
> +	struct io_context *ioc = current->io_context;
>  	struct io_cq *icq;
>  
>  	spin_lock_irq(&q->queue_lock);
> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
> index 7ff5671bf128..0f719c8532ae 100644
> --- a/block/blk-mq-sched.h
> +++ b/block/blk-mq-sched.h
> @@ -8,7 +8,7 @@
>  void blk_mq_sched_free_hctx_data(struct request_queue *q,
>  				 void (*exit)(struct blk_mq_hw_ctx *));
>  
> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
> +void blk_mq_sched_assign_ioc(struct request *rq);
>  
>  void blk_mq_sched_request_inserted(struct request *rq);
>  bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 32b246ed44c0..636f80b96fa6 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
>  	if (!op_is_flush(data->cmd_flags)) {
>  		rq->elv.icq = NULL;
>  		if (e && e->type->ops.prepare_request) {
> -			if (e->type->icq_cache && rq_ioc(bio))
> -				blk_mq_sched_assign_ioc(rq, bio);
> +			if (e->type->icq_cache)
> +				blk_mq_sched_assign_ioc(rq);
>  
>  			e->type->ops.prepare_request(rq, bio);
>  			rq->rq_flags |= RQF_ELVPRIV;
> diff --git a/block/blk.h b/block/blk.h
> index 816a9abb87cd..610948157a5b 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
>  
>  int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
>  
> -/**
> - * rq_ioc - determine io_context for request allocation
> - * @bio: request being allocated is for this bio (can be %NULL)
> - *
> - * Determine io_context to use for request allocation for @bio.  May return
> - * %NULL if %current->io_context doesn't exist.
> - */
> -static inline struct io_context *rq_ioc(struct bio *bio)
> -{
> -#ifdef CONFIG_BLK_CGROUP
> -	if (bio && bio->bi_ioc)
> -		return bio->bi_ioc;
> -#endif
> -	return current->io_context;
> -}
> -
>  /**
>   * create_io_context - try to create task->io_context
>   * @gfp_mask: allocation mask
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index dbdbfbd6a987..c0ba1a038ff3 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -174,10 +174,9 @@ struct bio {
>  	void			*bi_private;
>  #ifdef CONFIG_BLK_CGROUP
>  	/*
> -	 * Optional ioc and css associated with this bio.  Put on bio
> +	 * Optional css associated with this bio.  Put on bio
>  	 * release.  Read comment on top of bio_associate_current().
>  	 */
> -	struct io_context	*bi_ioc;
>  	struct cgroup_subsys_state *bi_css;
>  	struct blkcg_gq		*bi_blkg;
>  	struct bio_issue	bi_issue;

Hi,

Just found the following kernel oops, seems it is likely related with this
patch.

[  391.981012] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
[  391.982506] PGD 0 P4D 0
[  391.982975] Oops: 0000 [#1] PREEMPT SMP PTI
[  391.983769] CPU: 1 PID: 1790 Comm: scsi_id Not tainted 4.20.0-rc3_72abead3bf43_for-4.21-block-mp-bvec-V11+ #1
[  391.985563] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
[  391.987107] RIP: 0010:ioc_lookup_icq+0x13/0x54
[  391.987936] Code: f6 48 8b 3d 1c 78 5b 01 5b 5d 41 5c 41 5d 41 5e 41 5f e9 68 bd eb ff 0f 1f 44 00 00 55 53 48 89 fb 51 48 89 f5 e8 e3 82 da ff <48> 8b 43 38 48 85 c0 74 05 48 39 28 74 22 48 63 b5 8c 00 00 00 48
[  391.991318] RSP: 0018:ffffc90001467bb0 EFLAGS: 00010002
[  391.992292] RAX: ffff888266c85ac0 RBX: 0000000000000000 RCX: 0000000000000100
[  391.993615] RDX: 0000000000000001 RSI: ffff88826601f230 RDI: 0000000000000000
[  391.994917] RBP: ffff88826601f230 R08: 00000000f461df07 R09: 0000000000000006
[  391.996242] R10: ffffc90001467b10 R11: 0000000000000020 R12: ffff888269df4000
[  391.997572] R13: 0000000000000000 R14: ffff88826601f2c4 R15: 0000000000000001
[  391.998905] FS:  00007fa6923b7940(0000) GS:ffff888277a80000(0000) knlGS:0000000000000000
[  392.000389] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  392.001468] CR2: 0000000000000038 CR3: 0000000106dd8005 CR4: 0000000000760ee0
[  392.002783] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  392.004108] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  392.005394] PKRU: 55555554
[  392.005897] Call Trace:
[  392.006384]  blk_mq_sched_assign_ioc+0x3d/0x7f
[  392.007216]  blk_mq_get_request+0x321/0x354
[  392.008008]  blk_mq_alloc_request+0x4e/0xbf
[  392.008802]  blk_get_request+0x24/0x4c
[  392.009518]  sg_io+0x93/0x371
[  392.010074]  ? bd_acquire+0xa6/0xa6
[  392.010707]  ? dput+0x29/0xfd
[  392.011232]  ? mntput_no_expire+0x11/0x185
[  392.011987]  scsi_cmd_ioctl+0x1d3/0x386
[  392.012707]  sd_ioctl+0xbb/0xde [sd_mod]
[  392.013449]  blkdev_ioctl+0x893/0x8bf
[  392.014132]  block_ioctl+0x3c/0x3f
[  392.014781]  vfs_ioctl+0x1e/0x2b
[  392.015378]  do_vfs_ioctl+0x531/0x559
[  392.016059]  ksys_ioctl+0x3e/0x5d
[  392.016681]  __x64_sys_ioctl+0x16/0x19
[  392.017361]  do_syscall_64+0x84/0x13f
[  392.018060]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  392.018995] RIP: 0033:0x7fa691edf267
[  392.019663] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
[  392.023072] RSP: 002b:00007ffe463e8de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  392.024457] RAX: ffffffffffffffda RBX: 00007ffe463e8e20 RCX: 00007fa691edf267
[  392.025767] RDX: 00007ffe463e8e20 RSI: 0000000000002285 RDI: 0000000000000004
[  392.027068] RBP: 00007ffe463e9470 R08: 0000000000002006 R09: 00000000fffffe00
[  392.028413] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe463e9920
[  392.029722] R13: 00007ffe463e8e20 R14: 00007ffe463e8e2a R15: 00007ffe463e9920
[  392.031031] Modules linked in: scsi_debug null_blk isofs iTCO_wdt iTCO_vendor_support i2c_i801 i2c_core lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel virtio_scsi qemu_fw_cfg dm_mirror dm_region_hash dm_log dm_mod [last unloaded: null_blk]
[  392.035573] Dumping ftrace buffer:
[  392.036203]    (ftrace buffer empty)
[  392.036871] CR2: 0000000000000038
[  392.037503] ---[ end trace fa20a1088b068790 ]---

Thanks,
Ming

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Jens Axboe]

On 11/20/18 10:21 AM, Ming Lei wrote:
> On Mon, Nov 19, 2018 at 12:51:26PM +0900, Damien Le Moal wrote:
>> bio->bi_ioc is never set so always NULL. Remove references to it in
>> bio_disassociate_task() and in rq_ioc() and delete this field from
>> struct bio. With this change, rq_ioc() always returns
>> current->io_context without the need for a bio argument. Further
>> simplify the code and make it more readable by also removing this
>> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
>> removing its bio argument.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>>  block/bio.c               |  4 ----
>>  block/blk-core.c          |  2 +-
>>  block/blk-mq-sched.c      |  4 ++--
>>  block/blk-mq-sched.h      |  2 +-
>>  block/blk-mq.c            |  4 ++--
>>  block/blk.h               | 16 ----------------
>>  include/linux/blk_types.h |  3 +--
>>  7 files changed, 7 insertions(+), 28 deletions(-)
>>
>> diff --git a/block/bio.c b/block/bio.c
>> index 4f4d9884443b..03895cc0d74a 100644
>> --- a/block/bio.c
>> +++ b/block/bio.c
>> @@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
>>   */
>>  void bio_disassociate_task(struct bio *bio)
>>  {
>> -	if (bio->bi_ioc) {
>> -		put_io_context(bio->bi_ioc);
>> -		bio->bi_ioc = NULL;
>> -	}
>>  	if (bio->bi_css) {
>>  		css_put(bio->bi_css);
>>  		bio->bi_css = NULL;
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index d6e8ab9ca99d..492648c96992 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
>>  
>>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
>>  {
>> -	struct io_context *ioc = rq_ioc(bio);
>> +	struct io_context *ioc = current->io_context;
>>  
>>  	if (bio->bi_opf & REQ_RAHEAD)
>>  		req->cmd_flags |= REQ_FAILFAST_MASK;
>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>> index d084f731d104..13b8dc332541 100644
>> --- a/block/blk-mq-sched.c
>> +++ b/block/blk-mq-sched.c
>> @@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,
>>  }
>>  EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>  
>> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
>> +void blk_mq_sched_assign_ioc(struct request *rq)
>>  {
>>  	struct request_queue *q = rq->q;
>> -	struct io_context *ioc = rq_ioc(bio);
>> +	struct io_context *ioc = current->io_context;
>>  	struct io_cq *icq;
>>  
>>  	spin_lock_irq(&q->queue_lock);
>> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
>> index 7ff5671bf128..0f719c8532ae 100644
>> --- a/block/blk-mq-sched.h
>> +++ b/block/blk-mq-sched.h
>> @@ -8,7 +8,7 @@
>>  void blk_mq_sched_free_hctx_data(struct request_queue *q,
>>  				 void (*exit)(struct blk_mq_hw_ctx *));
>>  
>> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
>> +void blk_mq_sched_assign_ioc(struct request *rq);
>>  
>>  void blk_mq_sched_request_inserted(struct request *rq);
>>  bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 32b246ed44c0..636f80b96fa6 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
>>  	if (!op_is_flush(data->cmd_flags)) {
>>  		rq->elv.icq = NULL;
>>  		if (e && e->type->ops.prepare_request) {
>> -			if (e->type->icq_cache && rq_ioc(bio))
>> -				blk_mq_sched_assign_ioc(rq, bio);
>> +			if (e->type->icq_cache)
>> +				blk_mq_sched_assign_ioc(rq);
>>  
>>  			e->type->ops.prepare_request(rq, bio);
>>  			rq->rq_flags |= RQF_ELVPRIV;
>> diff --git a/block/blk.h b/block/blk.h
>> index 816a9abb87cd..610948157a5b 100644
>> --- a/block/blk.h
>> +++ b/block/blk.h
>> @@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
>>  
>>  int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
>>  
>> -/**
>> - * rq_ioc - determine io_context for request allocation
>> - * @bio: request being allocated is for this bio (can be %NULL)
>> - *
>> - * Determine io_context to use for request allocation for @bio.  May return
>> - * %NULL if %current->io_context doesn't exist.
>> - */
>> -static inline struct io_context *rq_ioc(struct bio *bio)
>> -{
>> -#ifdef CONFIG_BLK_CGROUP
>> -	if (bio && bio->bi_ioc)
>> -		return bio->bi_ioc;
>> -#endif
>> -	return current->io_context;
>> -}
>> -
>>  /**
>>   * create_io_context - try to create task->io_context
>>   * @gfp_mask: allocation mask
>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>> index dbdbfbd6a987..c0ba1a038ff3 100644
>> --- a/include/linux/blk_types.h
>> +++ b/include/linux/blk_types.h
>> @@ -174,10 +174,9 @@ struct bio {
>>  	void			*bi_private;
>>  #ifdef CONFIG_BLK_CGROUP
>>  	/*
>> -	 * Optional ioc and css associated with this bio.  Put on bio
>> +	 * Optional css associated with this bio.  Put on bio
>>  	 * release.  Read comment on top of bio_associate_current().
>>  	 */
>> -	struct io_context	*bi_ioc;
>>  	struct cgroup_subsys_state *bi_css;
>>  	struct blkcg_gq		*bi_blkg;
>>  	struct bio_issue	bi_issue;
> 
> Hi,
> 
> Just found the following kernel oops, seems it is likely related with this
> patch.
> 
> [  391.981012] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
> [  391.982506] PGD 0 P4D 0
> [  391.982975] Oops: 0000 [#1] PREEMPT SMP PTI
> [  391.983769] CPU: 1 PID: 1790 Comm: scsi_id Not tainted 4.20.0-rc3_72abead3bf43_for-4.21-block-mp-bvec-V11+ #1
> [  391.985563] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
> [  391.987107] RIP: 0010:ioc_lookup_icq+0x13/0x54
> [  391.987936] Code: f6 48 8b 3d 1c 78 5b 01 5b 5d 41 5c 41 5d 41 5e 41 5f e9 68 bd eb ff 0f 1f 44 00 00 55 53 48 89 fb 51 48 89 f5 e8 e3 82 da ff <48> 8b 43 38 48 85 c0 74 05 48 39 28 74 22 48 63 b5 8c 00 00 00 48
> [  391.991318] RSP: 0018:ffffc90001467bb0 EFLAGS: 00010002
> [  391.992292] RAX: ffff888266c85ac0 RBX: 0000000000000000 RCX: 0000000000000100
> [  391.993615] RDX: 0000000000000001 RSI: ffff88826601f230 RDI: 0000000000000000
> [  391.994917] RBP: ffff88826601f230 R08: 00000000f461df07 R09: 0000000000000006
> [  391.996242] R10: ffffc90001467b10 R11: 0000000000000020 R12: ffff888269df4000
> [  391.997572] R13: 0000000000000000 R14: ffff88826601f2c4 R15: 0000000000000001
> [  391.998905] FS:  00007fa6923b7940(0000) GS:ffff888277a80000(0000) knlGS:0000000000000000
> [  392.000389] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  392.001468] CR2: 0000000000000038 CR3: 0000000106dd8005 CR4: 0000000000760ee0
> [  392.002783] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  392.004108] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  392.005394] PKRU: 55555554
> [  392.005897] Call Trace:
> [  392.006384]  blk_mq_sched_assign_ioc+0x3d/0x7f
> [  392.007216]  blk_mq_get_request+0x321/0x354
> [  392.008008]  blk_mq_alloc_request+0x4e/0xbf
> [  392.008802]  blk_get_request+0x24/0x4c
> [  392.009518]  sg_io+0x93/0x371
> [  392.010074]  ? bd_acquire+0xa6/0xa6
> [  392.010707]  ? dput+0x29/0xfd
> [  392.011232]  ? mntput_no_expire+0x11/0x185
> [  392.011987]  scsi_cmd_ioctl+0x1d3/0x386
> [  392.012707]  sd_ioctl+0xbb/0xde [sd_mod]
> [  392.013449]  blkdev_ioctl+0x893/0x8bf
> [  392.014132]  block_ioctl+0x3c/0x3f
> [  392.014781]  vfs_ioctl+0x1e/0x2b
> [  392.015378]  do_vfs_ioctl+0x531/0x559
> [  392.016059]  ksys_ioctl+0x3e/0x5d
> [  392.016681]  __x64_sys_ioctl+0x16/0x19
> [  392.017361]  do_syscall_64+0x84/0x13f
> [  392.018060]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  392.018995] RIP: 0033:0x7fa691edf267
> [  392.019663] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
> [  392.023072] RSP: 002b:00007ffe463e8de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [  392.024457] RAX: ffffffffffffffda RBX: 00007ffe463e8e20 RCX: 00007fa691edf267
> [  392.025767] RDX: 00007ffe463e8e20 RSI: 0000000000002285 RDI: 0000000000000004
> [  392.027068] RBP: 00007ffe463e9470 R08: 0000000000002006 R09: 00000000fffffe00
> [  392.028413] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe463e9920
> [  392.029722] R13: 00007ffe463e8e20 R14: 00007ffe463e8e2a R15: 00007ffe463e9920
> [  392.031031] Modules linked in: scsi_debug null_blk isofs iTCO_wdt iTCO_vendor_support i2c_i801 i2c_core lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel virtio_scsi qemu_fw_cfg dm_mirror dm_region_hash dm_log dm_mod [last unloaded: null_blk]
> [  392.035573] Dumping ftrace buffer:
> [  392.036203]    (ftrace buffer empty)
> [  392.036871] CR2: 0000000000000038
> [  392.037503] ---[ end trace fa20a1088b068790 ]---

I think the below should fix it, we haven't necessarily setup an
ioc if we're just doing as passthrough request.


diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 13b8dc332541..f096d8989773 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
 void blk_mq_sched_assign_ioc(struct request *rq)
 {
 	struct request_queue *q = rq->q;
-	struct io_context *ioc = current->io_context;
+	struct io_context *ioc;
 	struct io_cq *icq;
 
+	/*
+	 * May not have an IO context if it's a passthrough request
+	 */
+	ioc = current->io_context;
+	if (!ioc)
+		return;
+
 	spin_lock_irq(&q->queue_lock);
 	icq = ioc_lookup_icq(ioc, q);
 	spin_unlock_irq(&q->queue_lock);

-- 
Jens Axboe

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

On 2018/11/21 2:31, Jens Axboe wrote:
> I think the below should fix it, we haven't necessarily setup an
> ioc if we're just doing as passthrough request.
> 
> 
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 13b8dc332541..f096d8989773 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>  void blk_mq_sched_assign_ioc(struct request *rq)
>  {
>  	struct request_queue *q = rq->q;
> -	struct io_context *ioc = current->io_context;
> +	struct io_context *ioc;
>  	struct io_cq *icq;
>  
> +	/*
> +	 * May not have an IO context if it's a passthrough request
> +	 */
> +	ioc = current->io_context;
> +	if (!ioc)
> +		return;
> +
>  	spin_lock_irq(&q->queue_lock);
>  	icq = ioc_lookup_icq(ioc, q);
>  	spin_unlock_irq(&q->queue_lock);

This seems reasonable to me, but I wonder why this problem was not triggering
before. The previous code getting the ioc with the rq_ioc(bio) call was
essentially the same and there was no "if (!ioc) return;" in
blk_mq_sched_assign_ioc() before the patch.
Any idea why this is popping up now ?

Ming,

Is this a new test your are running ? If this same problem triggers on stable
kernels, Jens patch needs to go to stable too.

Best regards.

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Ming Lei]

On Tue, Nov 20, 2018 at 11:58:09PM +0000, Damien Le Moal wrote:
> On 2018/11/21 2:31, Jens Axboe wrote:
> > I think the below should fix it, we haven't necessarily setup an
> > ioc if we're just doing as passthrough request.
> > 
> > 
> > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> > index 13b8dc332541..f096d8989773 100644
> > --- a/block/blk-mq-sched.c
> > +++ b/block/blk-mq-sched.c
> > @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
> >  void blk_mq_sched_assign_ioc(struct request *rq)
> >  {
> >  	struct request_queue *q = rq->q;
> > -	struct io_context *ioc = current->io_context;
> > +	struct io_context *ioc;
> >  	struct io_cq *icq;
> >  
> > +	/*
> > +	 * May not have an IO context if it's a passthrough request
> > +	 */
> > +	ioc = current->io_context;
> > +	if (!ioc)
> > +		return;
> > +
> >  	spin_lock_irq(&q->queue_lock);
> >  	icq = ioc_lookup_icq(ioc, q);
> >  	spin_unlock_irq(&q->queue_lock);
> 
> This seems reasonable to me, but I wonder why this problem was not triggering
> before. The previous code getting the ioc with the rq_ioc(bio) call was
> essentially the same and there was no "if (!ioc) return;" in
> blk_mq_sched_assign_ioc() before the patch.
> Any idea why this is popping up now ?
> 
> Ming,
> 
> Is this a new test your are running ? If this same problem triggers on stable
> kernels, Jens patch needs to go to stable too.

No, I run daily block related tests on block for-next, and this issue is
just triggered when your patches landed.

You may find the test script:

https://people.redhat.com/minlei/tests/tools/elv-switch

Thanks,
Ming

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

On 2018/11/21 10:24, Ming Lei wrote:
> On Tue, Nov 20, 2018 at 11:58:09PM +0000, Damien Le Moal wrote:
>> On 2018/11/21 2:31, Jens Axboe wrote:
>>> I think the below should fix it, we haven't necessarily setup an
>>> ioc if we're just doing as passthrough request.
>>>
>>>
>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>> index 13b8dc332541..f096d8989773 100644
>>> --- a/block/blk-mq-sched.c
>>> +++ b/block/blk-mq-sched.c
>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>>  {
>>>  	struct request_queue *q = rq->q;
>>> -	struct io_context *ioc = current->io_context;
>>> +	struct io_context *ioc;
>>>  	struct io_cq *icq;
>>>  
>>> +	/*
>>> +	 * May not have an IO context if it's a passthrough request
>>> +	 */
>>> +	ioc = current->io_context;
>>> +	if (!ioc)
>>> +		return;
>>> +
>>>  	spin_lock_irq(&q->queue_lock);
>>>  	icq = ioc_lookup_icq(ioc, q);
>>>  	spin_unlock_irq(&q->queue_lock);
>>
>> This seems reasonable to me, but I wonder why this problem was not triggering
>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>> essentially the same and there was no "if (!ioc) return;" in
>> blk_mq_sched_assign_ioc() before the patch.
>> Any idea why this is popping up now ?
>>
>> Ming,
>>
>> Is this a new test your are running ? If this same problem triggers on stable
>> kernels, Jens patch needs to go to stable too.
> 
> No, I run daily block related tests on block for-next, and this issue is
> just triggered when your patches landed.
> 
> You may find the test script:
> 
> https://people.redhat.com/minlei/tests/tools/elv-switch

Thanks for the information. I will look into what else caused the behavior change.


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Jens Axboe]

On 11/20/18 4:58 PM, Damien Le Moal wrote:
> On 2018/11/21 2:31, Jens Axboe wrote:
>> I think the below should fix it, we haven't necessarily setup an
>> ioc if we're just doing as passthrough request.
>>
>>
>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>> index 13b8dc332541..f096d8989773 100644
>> --- a/block/blk-mq-sched.c
>> +++ b/block/blk-mq-sched.c
>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>  {
>>  	struct request_queue *q = rq->q;
>> -	struct io_context *ioc = current->io_context;
>> +	struct io_context *ioc;
>>  	struct io_cq *icq;
>>  
>> +	/*
>> +	 * May not have an IO context if it's a passthrough request
>> +	 */
>> +	ioc = current->io_context;
>> +	if (!ioc)
>> +		return;
>> +
>>  	spin_lock_irq(&q->queue_lock);
>>  	icq = ioc_lookup_icq(ioc, q);
>>  	spin_unlock_irq(&q->queue_lock);
> 
> This seems reasonable to me, but I wonder why this problem was not triggering
> before. The previous code getting the ioc with the rq_ioc(bio) call was
> essentially the same and there was no "if (!ioc) return;" in
> blk_mq_sched_assign_ioc() before the patch.
> Any idea why this is popping up now ?
> 
> Ming,
> 
> Is this a new test your are running ? If this same problem triggers on stable
> kernels, Jens patch needs to go to stable too.

No, it's definitely introduced in your patches:

-                       if (e->type->icq_cache && rq_ioc(bio))
-                               blk_mq_sched_assign_ioc(rq, bio);
+                       if (e->type->icq_cache)
+                               blk_mq_sched_assign_ioc(rq);

Please run blktests on a series. Always. There's no excuse not to.

-- 
Jens Axboe

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

On 2018/11/21 11:11, Jens Axboe wrote:
> On 11/20/18 4:58 PM, Damien Le Moal wrote:
>> On 2018/11/21 2:31, Jens Axboe wrote:
>>> I think the below should fix it, we haven't necessarily setup an
>>> ioc if we're just doing as passthrough request.
>>>
>>>
>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>> index 13b8dc332541..f096d8989773 100644
>>> --- a/block/blk-mq-sched.c
>>> +++ b/block/blk-mq-sched.c
>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>>  {
>>>  	struct request_queue *q = rq->q;
>>> -	struct io_context *ioc = current->io_context;
>>> +	struct io_context *ioc;
>>>  	struct io_cq *icq;
>>>  
>>> +	/*
>>> +	 * May not have an IO context if it's a passthrough request
>>> +	 */
>>> +	ioc = current->io_context;
>>> +	if (!ioc)
>>> +		return;
>>> +
>>>  	spin_lock_irq(&q->queue_lock);
>>>  	icq = ioc_lookup_icq(ioc, q);
>>>  	spin_unlock_irq(&q->queue_lock);
>>
>> This seems reasonable to me, but I wonder why this problem was not triggering
>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>> essentially the same and there was no "if (!ioc) return;" in
>> blk_mq_sched_assign_ioc() before the patch.
>> Any idea why this is popping up now ?
>>
>> Ming,
>>
>> Is this a new test your are running ? If this same problem triggers on stable
>> kernels, Jens patch needs to go to stable too.
> 
> No, it's definitely introduced in your patches:
> 
> -                       if (e->type->icq_cache && rq_ioc(bio))
> -                               blk_mq_sched_assign_ioc(rq, bio);
> +                       if (e->type->icq_cache)
> +                               blk_mq_sched_assign_ioc(rq);

Arg ! Yes, I missed this. My apologies.

> Please run blktests on a series. Always. There's no excuse not to.

I did run my usual tests exercising drives with various fio workloads. But I did
not run blktests itself. I will fix my workflow to include it.

Thanks.


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

On 2018/11/21 11:11, Jens Axboe wrote:
> On 11/20/18 4:58 PM, Damien Le Moal wrote:
>> On 2018/11/21 2:31, Jens Axboe wrote:
>>> I think the below should fix it, we haven't necessarily setup an
>>> ioc if we're just doing as passthrough request.
>>>
>>>
>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>> index 13b8dc332541..f096d8989773 100644
>>> --- a/block/blk-mq-sched.c
>>> +++ b/block/blk-mq-sched.c
>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>>  {
>>>  	struct request_queue *q = rq->q;
>>> -	struct io_context *ioc = current->io_context;
>>> +	struct io_context *ioc;
>>>  	struct io_cq *icq;
>>>  
>>> +	/*
>>> +	 * May not have an IO context if it's a passthrough request
>>> +	 */
>>> +	ioc = current->io_context;
>>> +	if (!ioc)
>>> +		return;
>>> +
>>>  	spin_lock_irq(&q->queue_lock);
>>>  	icq = ioc_lookup_icq(ioc, q);
>>>  	spin_unlock_irq(&q->queue_lock);
>>
>> This seems reasonable to me, but I wonder why this problem was not triggering
>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>> essentially the same and there was no "if (!ioc) return;" in
>> blk_mq_sched_assign_ioc() before the patch.
>> Any idea why this is popping up now ?
>>
>> Ming,
>>
>> Is this a new test your are running ? If this same problem triggers on stable
>> kernels, Jens patch needs to go to stable too.
> 
> No, it's definitely introduced in your patches:
> 
> -                       if (e->type->icq_cache && rq_ioc(bio))
> -                               blk_mq_sched_assign_ioc(rq, bio);
> +                       if (e->type->icq_cache)
> +                               blk_mq_sched_assign_ioc(rq);
> 
> Please run blktests on a series. Always. There's no excuse not to.

By the way, should I send an updated patch 2 to include your fix ?
Or will you add an incremental fix ?

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Jens Axboe]

On 11/20/18 7:45 PM, Damien Le Moal wrote:
> On 2018/11/21 11:11, Jens Axboe wrote:
>> On 11/20/18 4:58 PM, Damien Le Moal wrote:
>>> On 2018/11/21 2:31, Jens Axboe wrote:
>>>> I think the below should fix it, we haven't necessarily setup an
>>>> ioc if we're just doing as passthrough request.
>>>>
>>>>
>>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>>> index 13b8dc332541..f096d8989773 100644
>>>> --- a/block/blk-mq-sched.c
>>>> +++ b/block/blk-mq-sched.c
>>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>>>  {
>>>>  	struct request_queue *q = rq->q;
>>>> -	struct io_context *ioc = current->io_context;
>>>> +	struct io_context *ioc;
>>>>  	struct io_cq *icq;
>>>>  
>>>> +	/*
>>>> +	 * May not have an IO context if it's a passthrough request
>>>> +	 */
>>>> +	ioc = current->io_context;
>>>> +	if (!ioc)
>>>> +		return;
>>>> +
>>>>  	spin_lock_irq(&q->queue_lock);
>>>>  	icq = ioc_lookup_icq(ioc, q);
>>>>  	spin_unlock_irq(&q->queue_lock);
>>>
>>> This seems reasonable to me, but I wonder why this problem was not triggering
>>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>>> essentially the same and there was no "if (!ioc) return;" in
>>> blk_mq_sched_assign_ioc() before the patch.
>>> Any idea why this is popping up now ?
>>>
>>> Ming,
>>>
>>> Is this a new test your are running ? If this same problem triggers on stable
>>> kernels, Jens patch needs to go to stable too.
>>
>> No, it's definitely introduced in your patches:
>>
>> -                       if (e->type->icq_cache && rq_ioc(bio))
>> -                               blk_mq_sched_assign_ioc(rq, bio);
>> +                       if (e->type->icq_cache)
>> +                               blk_mq_sched_assign_ioc(rq);
>>
>> Please run blktests on a series. Always. There's no excuse not to.
> 
> By the way, should I send an updated patch 2 to include your fix ?
> Or will you add an incremental fix ?

I had to add the incremental fix, I already merged your patches
earlier. It's all pushed out now.

-- 
Jens Axboe

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Damien Le Moal]

On 2018/11/21 11:49, Jens Axboe wrote:
> On 11/20/18 7:45 PM, Damien Le Moal wrote:
>> On 2018/11/21 11:11, Jens Axboe wrote:
>>> On 11/20/18 4:58 PM, Damien Le Moal wrote:
>>>> On 2018/11/21 2:31, Jens Axboe wrote:
>>>>> I think the below should fix it, we haven't necessarily setup an
>>>>> ioc if we're just doing as passthrough request.
>>>>>
>>>>>
>>>>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>>>>> index 13b8dc332541..f096d8989773 100644
>>>>> --- a/block/blk-mq-sched.c
>>>>> +++ b/block/blk-mq-sched.c
>>>>> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>>>>  void blk_mq_sched_assign_ioc(struct request *rq)
>>>>>  {
>>>>>  	struct request_queue *q = rq->q;
>>>>> -	struct io_context *ioc = current->io_context;
>>>>> +	struct io_context *ioc;
>>>>>  	struct io_cq *icq;
>>>>>  
>>>>> +	/*
>>>>> +	 * May not have an IO context if it's a passthrough request
>>>>> +	 */
>>>>> +	ioc = current->io_context;
>>>>> +	if (!ioc)
>>>>> +		return;
>>>>> +
>>>>>  	spin_lock_irq(&q->queue_lock);
>>>>>  	icq = ioc_lookup_icq(ioc, q);
>>>>>  	spin_unlock_irq(&q->queue_lock);
>>>>
>>>> This seems reasonable to me, but I wonder why this problem was not triggering
>>>> before. The previous code getting the ioc with the rq_ioc(bio) call was
>>>> essentially the same and there was no "if (!ioc) return;" in
>>>> blk_mq_sched_assign_ioc() before the patch.
>>>> Any idea why this is popping up now ?
>>>>
>>>> Ming,
>>>>
>>>> Is this a new test your are running ? If this same problem triggers on stable
>>>> kernels, Jens patch needs to go to stable too.
>>>
>>> No, it's definitely introduced in your patches:
>>>
>>> -                       if (e->type->icq_cache && rq_ioc(bio))
>>> -                               blk_mq_sched_assign_ioc(rq, bio);
>>> +                       if (e->type->icq_cache)
>>> +                               blk_mq_sched_assign_ioc(rq);
>>>
>>> Please run blktests on a series. Always. There's no excuse not to.
>>
>> By the way, should I send an updated patch 2 to include your fix ?
>> Or will you add an incremental fix ?
> 
> I had to add the incremental fix, I already merged your patches
> earlier. It's all pushed out now.

Thank you.


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/7] block: Remove bio->bi_ioc

[Ming Lei]

On Tue, Nov 20, 2018 at 10:31:19AM -0700, Jens Axboe wrote:
> On 11/20/18 10:21 AM, Ming Lei wrote:
> > On Mon, Nov 19, 2018 at 12:51:26PM +0900, Damien Le Moal wrote:
> >> bio->bi_ioc is never set so always NULL. Remove references to it in
> >> bio_disassociate_task() and in rq_ioc() and delete this field from
> >> struct bio. With this change, rq_ioc() always returns
> >> current->io_context without the need for a bio argument. Further
> >> simplify the code and make it more readable by also removing this
> >> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
> >> removing its bio argument.
> >>
> >> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> >> ---
> >>  block/bio.c               |  4 ----
> >>  block/blk-core.c          |  2 +-
> >>  block/blk-mq-sched.c      |  4 ++--
> >>  block/blk-mq-sched.h      |  2 +-
> >>  block/blk-mq.c            |  4 ++--
> >>  block/blk.h               | 16 ----------------
> >>  include/linux/blk_types.h |  3 +--
> >>  7 files changed, 7 insertions(+), 28 deletions(-)
> >>
> >> diff --git a/block/bio.c b/block/bio.c
> >> index 4f4d9884443b..03895cc0d74a 100644
> >> --- a/block/bio.c
> >> +++ b/block/bio.c
> >> @@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
> >>   */
> >>  void bio_disassociate_task(struct bio *bio)
> >>  {
> >> -	if (bio->bi_ioc) {
> >> -		put_io_context(bio->bi_ioc);
> >> -		bio->bi_ioc = NULL;
> >> -	}
> >>  	if (bio->bi_css) {
> >>  		css_put(bio->bi_css);
> >>  		bio->bi_css = NULL;
> >> diff --git a/block/blk-core.c b/block/blk-core.c
> >> index d6e8ab9ca99d..492648c96992 100644
> >> --- a/block/blk-core.c
> >> +++ b/block/blk-core.c
> >> @@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
> >>  
> >>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
> >>  {
> >> -	struct io_context *ioc = rq_ioc(bio);
> >> +	struct io_context *ioc = current->io_context;
> >>  
> >>  	if (bio->bi_opf & REQ_RAHEAD)
> >>  		req->cmd_flags |= REQ_FAILFAST_MASK;
> >> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> >> index d084f731d104..13b8dc332541 100644
> >> --- a/block/blk-mq-sched.c
> >> +++ b/block/blk-mq-sched.c
> >> @@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,
> >>  }
> >>  EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
> >>  
> >> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
> >> +void blk_mq_sched_assign_ioc(struct request *rq)
> >>  {
> >>  	struct request_queue *q = rq->q;
> >> -	struct io_context *ioc = rq_ioc(bio);
> >> +	struct io_context *ioc = current->io_context;
> >>  	struct io_cq *icq;
> >>  
> >>  	spin_lock_irq(&q->queue_lock);
> >> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
> >> index 7ff5671bf128..0f719c8532ae 100644
> >> --- a/block/blk-mq-sched.h
> >> +++ b/block/blk-mq-sched.h
> >> @@ -8,7 +8,7 @@
> >>  void blk_mq_sched_free_hctx_data(struct request_queue *q,
> >>  				 void (*exit)(struct blk_mq_hw_ctx *));
> >>  
> >> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
> >> +void blk_mq_sched_assign_ioc(struct request *rq);
> >>  
> >>  void blk_mq_sched_request_inserted(struct request *rq);
> >>  bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
> >> diff --git a/block/blk-mq.c b/block/blk-mq.c
> >> index 32b246ed44c0..636f80b96fa6 100644
> >> --- a/block/blk-mq.c
> >> +++ b/block/blk-mq.c
> >> @@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
> >>  	if (!op_is_flush(data->cmd_flags)) {
> >>  		rq->elv.icq = NULL;
> >>  		if (e && e->type->ops.prepare_request) {
> >> -			if (e->type->icq_cache && rq_ioc(bio))
> >> -				blk_mq_sched_assign_ioc(rq, bio);
> >> +			if (e->type->icq_cache)
> >> +				blk_mq_sched_assign_ioc(rq);
> >>  
> >>  			e->type->ops.prepare_request(rq, bio);
> >>  			rq->rq_flags |= RQF_ELVPRIV;
> >> diff --git a/block/blk.h b/block/blk.h
> >> index 816a9abb87cd..610948157a5b 100644
> >> --- a/block/blk.h
> >> +++ b/block/blk.h
> >> @@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
> >>  
> >>  int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
> >>  
> >> -/**
> >> - * rq_ioc - determine io_context for request allocation
> >> - * @bio: request being allocated is for this bio (can be %NULL)
> >> - *
> >> - * Determine io_context to use for request allocation for @bio.  May return
> >> - * %NULL if %current->io_context doesn't exist.
> >> - */
> >> -static inline struct io_context *rq_ioc(struct bio *bio)
> >> -{
> >> -#ifdef CONFIG_BLK_CGROUP
> >> -	if (bio && bio->bi_ioc)
> >> -		return bio->bi_ioc;
> >> -#endif
> >> -	return current->io_context;
> >> -}
> >> -
> >>  /**
> >>   * create_io_context - try to create task->io_context
> >>   * @gfp_mask: allocation mask
> >> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> >> index dbdbfbd6a987..c0ba1a038ff3 100644
> >> --- a/include/linux/blk_types.h
> >> +++ b/include/linux/blk_types.h
> >> @@ -174,10 +174,9 @@ struct bio {
> >>  	void			*bi_private;
> >>  #ifdef CONFIG_BLK_CGROUP
> >>  	/*
> >> -	 * Optional ioc and css associated with this bio.  Put on bio
> >> +	 * Optional css associated with this bio.  Put on bio
> >>  	 * release.  Read comment on top of bio_associate_current().
> >>  	 */
> >> -	struct io_context	*bi_ioc;
> >>  	struct cgroup_subsys_state *bi_css;
> >>  	struct blkcg_gq		*bi_blkg;
> >>  	struct bio_issue	bi_issue;
> > 
> > Hi,
> > 
> > Just found the following kernel oops, seems it is likely related with this
> > patch.
> > 
> > [  391.981012] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
> > [  391.982506] PGD 0 P4D 0
> > [  391.982975] Oops: 0000 [#1] PREEMPT SMP PTI
> > [  391.983769] CPU: 1 PID: 1790 Comm: scsi_id Not tainted 4.20.0-rc3_72abead3bf43_for-4.21-block-mp-bvec-V11+ #1
> > [  391.985563] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
> > [  391.987107] RIP: 0010:ioc_lookup_icq+0x13/0x54
> > [  391.987936] Code: f6 48 8b 3d 1c 78 5b 01 5b 5d 41 5c 41 5d 41 5e 41 5f e9 68 bd eb ff 0f 1f 44 00 00 55 53 48 89 fb 51 48 89 f5 e8 e3 82 da ff <48> 8b 43 38 48 85 c0 74 05 48 39 28 74 22 48 63 b5 8c 00 00 00 48
> > [  391.991318] RSP: 0018:ffffc90001467bb0 EFLAGS: 00010002
> > [  391.992292] RAX: ffff888266c85ac0 RBX: 0000000000000000 RCX: 0000000000000100
> > [  391.993615] RDX: 0000000000000001 RSI: ffff88826601f230 RDI: 0000000000000000
> > [  391.994917] RBP: ffff88826601f230 R08: 00000000f461df07 R09: 0000000000000006
> > [  391.996242] R10: ffffc90001467b10 R11: 0000000000000020 R12: ffff888269df4000
> > [  391.997572] R13: 0000000000000000 R14: ffff88826601f2c4 R15: 0000000000000001
> > [  391.998905] FS:  00007fa6923b7940(0000) GS:ffff888277a80000(0000) knlGS:0000000000000000
> > [  392.000389] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  392.001468] CR2: 0000000000000038 CR3: 0000000106dd8005 CR4: 0000000000760ee0
> > [  392.002783] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [  392.004108] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > [  392.005394] PKRU: 55555554
> > [  392.005897] Call Trace:
> > [  392.006384]  blk_mq_sched_assign_ioc+0x3d/0x7f
> > [  392.007216]  blk_mq_get_request+0x321/0x354
> > [  392.008008]  blk_mq_alloc_request+0x4e/0xbf
> > [  392.008802]  blk_get_request+0x24/0x4c
> > [  392.009518]  sg_io+0x93/0x371
> > [  392.010074]  ? bd_acquire+0xa6/0xa6
> > [  392.010707]  ? dput+0x29/0xfd
> > [  392.011232]  ? mntput_no_expire+0x11/0x185
> > [  392.011987]  scsi_cmd_ioctl+0x1d3/0x386
> > [  392.012707]  sd_ioctl+0xbb/0xde [sd_mod]
> > [  392.013449]  blkdev_ioctl+0x893/0x8bf
> > [  392.014132]  block_ioctl+0x3c/0x3f
> > [  392.014781]  vfs_ioctl+0x1e/0x2b
> > [  392.015378]  do_vfs_ioctl+0x531/0x559
> > [  392.016059]  ksys_ioctl+0x3e/0x5d
> > [  392.016681]  __x64_sys_ioctl+0x16/0x19
> > [  392.017361]  do_syscall_64+0x84/0x13f
> > [  392.018060]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [  392.018995] RIP: 0033:0x7fa691edf267
> > [  392.019663] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
> > [  392.023072] RSP: 002b:00007ffe463e8de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > [  392.024457] RAX: ffffffffffffffda RBX: 00007ffe463e8e20 RCX: 00007fa691edf267
> > [  392.025767] RDX: 00007ffe463e8e20 RSI: 0000000000002285 RDI: 0000000000000004
> > [  392.027068] RBP: 00007ffe463e9470 R08: 0000000000002006 R09: 00000000fffffe00
> > [  392.028413] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe463e9920
> > [  392.029722] R13: 00007ffe463e8e20 R14: 00007ffe463e8e2a R15: 00007ffe463e9920
> > [  392.031031] Modules linked in: scsi_debug null_blk isofs iTCO_wdt iTCO_vendor_support i2c_i801 i2c_core lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel virtio_scsi qemu_fw_cfg dm_mirror dm_region_hash dm_log dm_mod [last unloaded: null_blk]
> > [  392.035573] Dumping ftrace buffer:
> > [  392.036203]    (ftrace buffer empty)
> > [  392.036871] CR2: 0000000000000038
> > [  392.037503] ---[ end trace fa20a1088b068790 ]---
> 
> I think the below should fix it, we haven't necessarily setup an
> ioc if we're just doing as passthrough request.
> 
> 
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 13b8dc332541..f096d8989773 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>  void blk_mq_sched_assign_ioc(struct request *rq)
>  {
>  	struct request_queue *q = rq->q;
> -	struct io_context *ioc = current->io_context;
> +	struct io_context *ioc;
>  	struct io_cq *icq;
>  
> +	/*
> +	 * May not have an IO context if it's a passthrough request
> +	 */
> +	ioc = current->io_context;
> +	if (!ioc)
> +		return;
> +
>  	spin_lock_irq(&q->queue_lock);
>  	icq = ioc_lookup_icq(ioc, q);
>  	spin_unlock_irq(&q->queue_lock);

Looks this patch fixes the kernel panic in elevator stress switch test.

Tested-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming

[PATCH 3/7] block: Fix get_task_ioprio() default return value

[Damien Le Moal]

As explained in ioprio_get() and ionice man pages, the default I/O
priority class for processes which have not set an I/O priority using
ioprio_set() is IOPRIO_CLASS_BE and not IOPRIO_CLASS_NONE.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/ioprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index f9821080c92c..ea5be206eb26 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -163,7 +163,7 @@ static int get_task_ioprio(struct task_struct *p)
 	ret = security_task_getioprio(p);
 	if (ret)
 		goto out;
-	ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
+	ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
 	task_lock(p);
 	if (p->io_context)
 		ret = p->io_context->ioprio;
-- 
2.19.1

Re: [PATCH 3/7] block: Fix get_task_ioprio() default return value

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:27PM +0900, Damien Le Moal wrote:
> As explained in ioprio_get() and ionice man pages, the default I/O
> priority class for processes which have not set an I/O priority using
> ioprio_set() is IOPRIO_CLASS_BE and not IOPRIO_CLASS_NONE.

While this matches the documentation, we've returned the current
values for 10 years, and before that plain 0 without any ioprio
magic.  It might be safer to just fix the documentation.

Re: [PATCH 3/7] block: Fix get_task_ioprio() default return value

[Damien Le Moal]

On Mon, 2018-11-19 at 00:16 -0800, Christoph Hellwig wrote:
> On Mon, Nov 19, 2018 at 12:51:27PM +0900, Damien Le Moal wrote:
> > As explained in ioprio_get() and ionice man pages, the default I/O
> > priority class for processes which have not set an I/O priority
> > using
> > ioprio_set() is IOPRIO_CLASS_BE and not IOPRIO_CLASS_NONE.
> 
> While this matches the documentation, we've returned the current
> values for 10 years, and before that plain 0 without any ioprio
> magic.  It might be safer to just fix the documentation.

OK. Will send a patch to fix the man pages.

[PATCH 4/7] block: Introduce get_current_ioprio()

[Damien Le Moal]

Define get_current_ioprio() as an inline helper to obtain the caller
I/O priority from its task I/O context. Use this helper in
blk_init_request_from_bio() to set a request ioprio.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/blk-core.c       |  6 +-----
 include/linux/ioprio.h | 13 +++++++++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 492648c96992..4450d3c08f25 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -813,18 +813,14 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
 
 void blk_init_request_from_bio(struct request *req, struct bio *bio)
 {
-	struct io_context *ioc = current->io_context;
-
 	if (bio->bi_opf & REQ_RAHEAD)
 		req->cmd_flags |= REQ_FAILFAST_MASK;
 
 	req->__sector = bio->bi_iter.bi_sector;
 	if (ioprio_valid(bio_prio(bio)))
 		req->ioprio = bio_prio(bio);
-	else if (ioc)
-		req->ioprio = ioc->ioprio;
 	else
-		req->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+		req->ioprio = get_current_ioprio();
 	req->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(req->q, req, bio);
 }
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 9e30ed6443db..e9bfe6972aed 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -70,6 +70,19 @@ static inline int task_nice_ioclass(struct task_struct *task)
 		return IOPRIO_CLASS_BE;
 }
 
+/*
+ * If the calling process has set an I/O priority, use that. Otherwise, return
+ * the default I/O priority.
+ */
+static inline int get_current_ioprio(void)
+{
+	struct io_context *ioc = current->io_context;
+
+	if (ioc)
+		return ioc->ioprio;
+	return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+}
+
 /*
  * For inheritance, return the highest of the two given priorities
  */
-- 
2.19.1

Re: [PATCH 4/7] block: Introduce get_current_ioprio()

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:28PM +0900, Damien Le Moal wrote:
> Define get_current_ioprio() as an inline helper to obtain the caller
> I/O priority from its task I/O context. Use this helper in
> blk_init_request_from_bio() to set a request ioprio.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 4/7] block: Introduce get_current_ioprio()

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

-- 
Johannes Thumshirn                                        SUSE Labs
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 4/7] block: Introduce get_current_ioprio()

[Adam Manzanares]

On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote:
> Define get_current_ioprio() as an inline helper to obtain the caller
> I/O priority from its task I/O context. Use this helper in
> blk_init_request_from_bio() to set a request ioprio.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>  block/blk-core.c       |  6 +-----
>  include/linux/ioprio.h | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 492648c96992..4450d3c08f25 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -813,18 +813,14 @@ unsigned int blk_plug_queued_count(struct
> request_queue *q)
>  
>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
>  {
> -	struct io_context *ioc = current->io_context;
> -
>  	if (bio->bi_opf & REQ_RAHEAD)
>  		req->cmd_flags |= REQ_FAILFAST_MASK;
>  
>  	req->__sector = bio->bi_iter.bi_sector;
>  	if (ioprio_valid(bio_prio(bio)))
>  		req->ioprio = bio_prio(bio);
> -	else if (ioc)
> -		req->ioprio = ioc->ioprio;
>  	else
> -		req->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
> +		req->ioprio = get_current_ioprio();
>  	req->write_hint = bio->bi_write_hint;
>  	blk_rq_bio_prep(req->q, req, bio);
>  }
> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
> index 9e30ed6443db..e9bfe6972aed 100644
> --- a/include/linux/ioprio.h
> +++ b/include/linux/ioprio.h
> @@ -70,6 +70,19 @@ static inline int task_nice_ioclass(struct
> task_struct *task)
>  		return IOPRIO_CLASS_BE;
>  }
>  
> +/*
> + * If the calling process has set an I/O priority, use that.
> Otherwise, return
> + * the default I/O priority.
> + */
> +static inline int get_current_ioprio(void)
> +{
> +	struct io_context *ioc = current->io_context;
> +
> +	if (ioc)
> +		return ioc->ioprio;
> +	return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);

Shouldn't this be IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM) to be
consistent with patch 3?


> +}
> +
>  /*
>   * For inheritance, return the highest of the two given priorities
>   */

Re: [PATCH 4/7] block: Introduce get_current_ioprio()

[Damien Le Moal]

Adam,

On 2018/11/20 3:18, Adam Manzanares wrote:
> On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote:
>> Define get_current_ioprio() as an inline helper to obtain the caller
>> I/O priority from its task I/O context. Use this helper in
>> blk_init_request_from_bio() to set a request ioprio.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>>  block/blk-core.c       |  6 +-----
>>  include/linux/ioprio.h | 13 +++++++++++++
>>  2 files changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 492648c96992..4450d3c08f25 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -813,18 +813,14 @@ unsigned int blk_plug_queued_count(struct
>> request_queue *q)
>>  
>>  void blk_init_request_from_bio(struct request *req, struct bio *bio)
>>  {
>> -	struct io_context *ioc = current->io_context;
>> -
>>  	if (bio->bi_opf & REQ_RAHEAD)
>>  		req->cmd_flags |= REQ_FAILFAST_MASK;
>>  
>>  	req->__sector = bio->bi_iter.bi_sector;
>>  	if (ioprio_valid(bio_prio(bio)))
>>  		req->ioprio = bio_prio(bio);
>> -	else if (ioc)
>> -		req->ioprio = ioc->ioprio;
>>  	else
>> -		req->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
>> +		req->ioprio = get_current_ioprio();
>>  	req->write_hint = bio->bi_write_hint;
>>  	blk_rq_bio_prep(req->q, req, bio);
>>  }
>> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
>> index 9e30ed6443db..e9bfe6972aed 100644
>> --- a/include/linux/ioprio.h
>> +++ b/include/linux/ioprio.h
>> @@ -70,6 +70,19 @@ static inline int task_nice_ioclass(struct
>> task_struct *task)
>>  		return IOPRIO_CLASS_BE;
>>  }
>>  
>> +/*
>> + * If the calling process has set an I/O priority, use that.
>> Otherwise, return
>> + * the default I/O priority.
>> + */
>> +static inline int get_current_ioprio(void)
>> +{
>> +	struct io_context *ioc = current->io_context;
>> +
>> +	if (ioc)
>> +		return ioc->ioprio;
>> +	return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
> 
> Shouldn't this be IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM) to be
> consistent with patch 3?

I do not think so. The effective I/O priority used in the case of NONE/0 is
determined by the scheduler. See the use of task_nice_ioprio() and
task_nice_ioclass() in cfq and bfq. So using NONE/0 is correct here I think.
Using BE/NORM would render all ioprio_valid() tests useless as BE/NORM is a
valid I/O priority.

Thinking more of it now, I think patch 3 should actually return by default
IOPRIO_PRIO_VALUE(task_nice_ioprio(), task_nice_ioclass()) rather than BE/NORM
as this value is only valid if (1) cfq or bfq are in use AND (2) the task
scheduling priority and nice values are the default.

In any case, I am dropping patch 3 as suggested by Christoph. We can try to
revisit this later making sure in the process that user land does not break (if
that is at all possible).

Best regards.

-- 
Damien Le Moal
Western Digital Research

[PATCH 5/7] aio: Fix fallback I/O priority value

[Damien Le Moal]

For cases when the application does not specify aio_reqprio for an aio,
fallback to use get_current_ioprio() to obtain the task I/O priority
last set using ioprio_set() rather than the hardcoded IOPRIO_CLASS_NONE
value.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 fs/aio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/aio.c b/fs/aio.c
index 301e6314183b..b984918be4b7 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1441,7 +1441,7 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
 
 		req->ki_ioprio = iocb->aio_reqprio;
 	} else
-		req->ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+		req->ki_ioprio = get_current_ioprio();
 
 	ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
 	if (unlikely(ret))
-- 
2.19.1

Re: [PATCH 5/7] aio: Fix fallback I/O priority value

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:29PM +0900, Damien Le Moal wrote:
> For cases when the application does not specify aio_reqprio for an aio,
> fallback to use get_current_ioprio() to obtain the task I/O priority
> last set using ioprio_set() rather than the hardcoded IOPRIO_CLASS_NONE
> value.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 5/7] aio: Fix fallback I/O priority value

[Johannes Thumshirn]

Looks good,
Reiewed-by: Johannes Thumshirn <jthumshirn@suse.de>

-- 
Johannes Thumshirn                                        SUSE Labs
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

Re: [PATCH 5/7] aio: Fix fallback I/O priority value

[Adam Manzanares]

On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote:
> For cases when the application does not specify aio_reqprio for an
> aio,
> fallback to use get_current_ioprio() to obtain the task I/O priority
> last set using ioprio_set() rather than the hardcoded
> IOPRIO_CLASS_NONE
> value.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>

> ---
>  fs/aio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/aio.c b/fs/aio.c
> index 301e6314183b..b984918be4b7 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1441,7 +1441,7 @@ static int aio_prep_rw(struct kiocb *req,
> struct iocb *iocb)
>  
>  		req->ki_ioprio = iocb->aio_reqprio;
>  	} else
> -		req->ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE,
> 0);
> +		req->ki_ioprio = get_current_ioprio();
>  
>  	ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
>  	if (unlikely(ret))

[PATCH 6/7] block: prevent merging of requests with different priorities

[Damien Le Moal]

Growing in size a high priority request by merging it with a lower
priority BIO or request will increase the request execution time. This
is the opposite result of the desired effect of high I/O priorities,
namely getting low I/O latencies. Prevent merging of requests and BIOs
that have different I/O priorities to fix this.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/blk-core.c  |  3 ---
 block/blk-merge.c | 14 ++++++++++++--
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 4450d3c08f25..dde30b08aa14 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -662,7 +662,6 @@ bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
 	req->biotail->bi_next = bio;
 	req->biotail = bio;
 	req->__data_len += bio->bi_iter.bi_size;
-	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
 
 	blk_account_io_start(req, false);
 	return true;
@@ -686,7 +685,6 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
 
 	req->__sector = bio->bi_iter.bi_sector;
 	req->__data_len += bio->bi_iter.bi_size;
-	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
 
 	blk_account_io_start(req, false);
 	return true;
@@ -706,7 +704,6 @@ bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
 	req->biotail->bi_next = bio;
 	req->biotail = bio;
 	req->__data_len += bio->bi_iter.bi_size;
-	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
 	req->nr_phys_segments = segments + 1;
 
 	blk_account_io_start(req, false);
diff --git a/block/blk-merge.c b/block/blk-merge.c
index b1df622cbd85..129f554d250d 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -752,6 +752,12 @@ static struct request *attempt_merge(struct request_queue *q,
 	if (req->write_hint != next->write_hint)
 		return NULL;
 
+	/*
+	 * Don't allow merge of different I/O priorities.
+	 */
+	if (req->ioprio != next->ioprio)
+		return NULL;
+
 	/*
 	 * If we are allowed to merge, then append bio list
 	 * from next to rq and release next. merge_requests_fn
@@ -807,8 +813,6 @@ static struct request *attempt_merge(struct request_queue *q,
 	 */
 	blk_account_io_merge(next);
 
-	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
-
 	/*
 	 * ownership of bio passed from next to req, return 'next' for
 	 * the caller to free
@@ -883,6 +887,12 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (rq->write_hint != bio->bi_write_hint)
 		return false;
 
+	/*
+	 * Don't allow merge of different I/O priorities.
+	 */
+	if (rq->ioprio != bio_prio(bio))
+		return false;
+
 	return true;
 }
 
-- 
2.19.1

Re: [PATCH 6/7] block: prevent merging of requests with different priorities

[Christoph Hellwig]

> +	/*
> +	 * Don't allow merge of different I/O priorities.
> +	 */
> +	if (req->ioprio != next->ioprio)
> +		return NULL;

> +	/*
> +	 * Don't allow merge of different I/O priorities.
> +	 */
> +	if (rq->ioprio != bio_prio(bio))
> +		return false;
> +

These comments just restate what is obvious in the code.  I would
recommend to drop them.

Re: [PATCH 6/7] block: prevent merging of requests with different priorities

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

-- 
Johannes Thumshirn                                        SUSE Labs
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850

[PATCH 7/7] block: Initialize BIO I/O priority early

[Damien Le Moal]

For the synchronous I/O path case (read(), write() etc system calls), a
BIO I/O priority is not initialized until the execution of
blk_init_request_from_bio() when the BIO is submitted and a request
initialized for the BIO execution. This is due to the ki_ioprio field of
the struct kiocb defined on stack being always initialized to
IOPRIO_CLASS_NONE, regardless of the calling process I/O context ioprio
value set with ioprio_set(). This late initialization can result in the
BIO being merged to pending requests even when the I/O priorities
differ.

Fix this by initializing the ki_iopriority field of on stack struct
kiocb using the get_current_ioprio() helper, ensuring that all BIOs
allocated and submitted for the system call execution see the correct
intended I/O priority early. With this, since a BIO I/O priority is
always set to the intended effective value for both the sync and async
path, blk_init_request_from_bio() can be simplified.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/blk-core.c   | 5 +----
 include/linux/fs.h | 2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index dde30b08aa14..04f5be473638 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -814,10 +814,7 @@ void blk_init_request_from_bio(struct request *req, struct bio *bio)
 		req->cmd_flags |= REQ_FAILFAST_MASK;
 
 	req->__sector = bio->bi_iter.bi_sector;
-	if (ioprio_valid(bio_prio(bio)))
-		req->ioprio = bio_prio(bio);
-	else
-		req->ioprio = get_current_ioprio();
+	req->ioprio = bio_prio(bio);
 	req->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(req->q, req, bio);
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c95c0807471f..a1ab233e6469 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2021,7 +2021,7 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 		.ki_filp = filp,
 		.ki_flags = iocb_flags(filp),
 		.ki_hint = ki_hint_validate(file_write_hint(filp)),
-		.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0),
+		.ki_ioprio = get_current_ioprio(),
 	};
 }
 
-- 
2.19.1

Re: [PATCH 7/7] block: Initialize BIO I/O priority early

[Christoph Hellwig]

On Mon, Nov 19, 2018 at 12:51:31PM +0900, Damien Le Moal wrote:
> For the synchronous I/O path case (read(), write() etc system calls), a
> BIO I/O priority is not initialized until the execution of
> blk_init_request_from_bio() when the BIO is submitted and a request
> initialized for the BIO execution. This is due to the ki_ioprio field of
> the struct kiocb defined on stack being always initialized to
> IOPRIO_CLASS_NONE, regardless of the calling process I/O context ioprio
> value set with ioprio_set(). This late initialization can result in the
> BIO being merged to pending requests even when the I/O priorities
> differ.
> 
> Fix this by initializing the ki_iopriority field of on stack struct
> kiocb using the get_current_ioprio() helper, ensuring that all BIOs
> allocated and submitted for the system call execution see the correct
> intended I/O priority early. With this, since a BIO I/O priority is
> always set to the intended effective value for both the sync and async
> path, blk_init_request_from_bio() can be simplified.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 7/7] block: Initialize BIO I/O priority early

[Adam Manzanares]

On Mon, 2018-11-19 at 12:51 +0900, Damien Le Moal wrote:
> For the synchronous I/O path case (read(), write() etc system calls),
> a
> BIO I/O priority is not initialized until the execution of
> blk_init_request_from_bio() when the BIO is submitted and a request
> initialized for the BIO execution. This is due to the ki_ioprio field
> of
> the struct kiocb defined on stack being always initialized to
> IOPRIO_CLASS_NONE, regardless of the calling process I/O context
> ioprio
> value set with ioprio_set(). This late initialization can result in
> the
> BIO being merged to pending requests even when the I/O priorities
> differ.
> 
> Fix this by initializing the ki_iopriority field of on stack struct
> kiocb using the get_current_ioprio() helper, ensuring that all BIOs
> allocated and submitted for the system call execution see the correct
> intended I/O priority early. With this, since a BIO I/O priority is
> always set to the intended effective value for both the sync and
> async
> path, blk_init_request_from_bio() can be simplified.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Nice cleanup, looks good. Thanks Damien.

Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>


> ---
>  block/blk-core.c   | 5 +----
>  include/linux/fs.h | 2 +-
>  2 files changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index dde30b08aa14..04f5be473638 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -814,10 +814,7 @@ void blk_init_request_from_bio(struct request
> *req, struct bio *bio)
>  		req->cmd_flags |= REQ_FAILFAST_MASK;
>  
>  	req->__sector = bio->bi_iter.bi_sector;
> -	if (ioprio_valid(bio_prio(bio)))
> -		req->ioprio = bio_prio(bio);
> -	else
> -		req->ioprio = get_current_ioprio();
> +	req->ioprio = bio_prio(bio);
>  	req->write_hint = bio->bi_write_hint;
>  	blk_rq_bio_prep(req->q, req, bio);
>  }
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c95c0807471f..a1ab233e6469 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2021,7 +2021,7 @@ static inline void init_sync_kiocb(struct kiocb
> *kiocb, struct file *filp)
>  		.ki_filp = filp,
>  		.ki_flags = iocb_flags(filp),
>  		.ki_hint = ki_hint_validate(file_write_hint(filp)),
> -		.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0),
> +		.ki_ioprio = get_current_ioprio(),
>  	};
>  }
>