[PATCH v2 0/4] IO priority fixes and improvements

[PATCH v2 0/4] IO priority fixes and improvements

[Damien Le Moal]

This series fixes problems with IO priority values handling and cleans
up several macro names and code for clarity.

Changes from v1:
* Added patch 4 to unify the default priority value used in various
  places.
* Fixed patch 2 as suggested by Bart: remove extra parenthesis and move
  ioprio_valid() from the uapi header to the kernel header.
* In patch 2, add priority value masking.

Damien Le Moal (4):
  block: bfq: fix bfq_set_next_ioprio_data()
  block: fix ioprio interface
  block: rename IOPRIO_BE_NR
  block: fix default IO priority handling

 block/bfq-iosched.c          | 10 +++++-----
 block/bfq-iosched.h          |  4 ++--
 block/bfq-wf2q.c             |  6 +++---
 block/ioprio.c               |  9 ++++-----
 drivers/nvme/host/lightnvm.c |  2 +-
 fs/f2fs/sysfs.c              |  2 +-
 include/linux/ioprio.h       | 22 ++++++++++++++++++----
 include/uapi/linux/ioprio.h  | 23 +++++++++++++----------
 8 files changed, 47 insertions(+), 31 deletions(-)

-- 
2.31.1

[PATCH v2 1/4] block: bfq: fix bfq_set_next_ioprio_data()

[Damien Le Moal]

For a request that has a priority level equal to or larger than
IOPRIO_BE_NR, bfq_set_next_ioprio_data() prints a critical warning but
defaults to setting the request new_ioprio field to IOPRIO_BE_NR. This
is not consistent with the warning and the allowed values for priority
levels. Fix this by setting the request new_ioprio field to
IOPRIO_BE_NR - 1, the lowest priority level allowed.

Cc: <stable@vger.kernel.org>
Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 727955918563..1f38d75524ae 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5293,7 +5293,7 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
 	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
 		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
 			bfqq->new_ioprio);
-		bfqq->new_ioprio = IOPRIO_BE_NR;
+		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
 	}
 
 	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
-- 
2.31.1

[PATCH v2 2/4] block: fix ioprio interface

[Damien Le Moal]

An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
in the block layer. E.g. ioprio_check_cap() takes an int as argument.
With such implicit int casting function calls, the upper 16-bits of the
int argument may be left uninitialized by the compiler, resulting in
invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
and in an error return for functions such as ioprio_check_cap().

Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
defines the 3-bits mask for the priority class.

While at it, cleanup the following:
* Apply the mask IOPRIO_PRIO_MASK to the data argument of the
  IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
* Remove unnecessary parenthesis around fixed values in the macro
  definitions in include/uapi/linux/ioprio.h.
* Update the outdated mention of CFQ in the comment describing priority
  classes and instead mention BFQ and mq-deadline.
* Change the argument name of the IOPRIO_PRIO_CLASS() and
  IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
  that an IO priority value should be passed rather than a mask.
* Change the ioprio_valid() macro into an inline function, adding a
  check on the maximum value of the class of a priority value as
  defined by the IOPRIO_CLASS_MAX enum value. Move this function to
  the kernel side in include/linux/ioprio.h.
* Remove the unnecessary "else" after the return statements in
  task_nice_ioclass().

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 include/linux/ioprio.h      | 15 ++++++++++++---
 include/uapi/linux/ioprio.h | 19 +++++++++++--------
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index ef9ad4fb245f..9b3a6d8172b4 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -8,6 +8,16 @@
 
 #include <uapi/linux/ioprio.h>
 
+/*
+ * Check that a priority value has a valid class.
+ */
+static inline bool ioprio_valid(unsigned short ioprio)
+{
+	unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
+
+	return class > IOPRIO_CLASS_NONE && class < IOPRIO_CLASS_MAX;
+}
+
 /*
  * if process has set io priority explicitly, use that. if not, convert
  * the cpu scheduler nice value to an io priority
@@ -25,10 +35,9 @@ static inline int task_nice_ioclass(struct task_struct *task)
 {
 	if (task->policy == SCHED_IDLE)
 		return IOPRIO_CLASS_IDLE;
-	else if (task_is_realtime(task))
+	if (task_is_realtime(task))
 		return IOPRIO_CLASS_RT;
-	else
-		return IOPRIO_CLASS_BE;
+	return IOPRIO_CLASS_BE;
 }
 
 /*
diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index 77b17e08b0da..abc40965aa96 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -5,12 +5,15 @@
 /*
  * Gives us 8 prio classes with 13-bits of data for each class
  */
-#define IOPRIO_CLASS_SHIFT	(13)
+#define IOPRIO_CLASS_SHIFT	13
+#define IOPRIO_CLASS_MASK	0x07
 #define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
 
-#define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
-#define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
-#define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)
+#define IOPRIO_PRIO_CLASS(ioprio)	\
+	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
+#define IOPRIO_PRIO_DATA(ioprio)	((ioprio) & IOPRIO_PRIO_MASK)
+#define IOPRIO_PRIO_VALUE(class, data)	\
+	(((class) << IOPRIO_CLASS_SHIFT) | ((data) & IOPRIO_PRIO_MASK))
 
 /*
  * These are the io priority groups as implemented by CFQ. RT is the realtime
@@ -23,14 +26,14 @@ enum {
 	IOPRIO_CLASS_RT,
 	IOPRIO_CLASS_BE,
 	IOPRIO_CLASS_IDLE,
-};
 
-#define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
+	IOPRIO_CLASS_MAX,
+};
 
 /*
  * 8 best effort priority levels are supported
  */
-#define IOPRIO_BE_NR	(8)
+#define IOPRIO_BE_NR	8
 
 enum {
 	IOPRIO_WHO_PROCESS = 1,
@@ -41,6 +44,6 @@ enum {
 /*
  * Fallback BE priority
  */
-#define IOPRIO_NORM	(4)
+#define IOPRIO_NORM	4
 
 #endif /* _UAPI_LINUX_IOPRIO_H */
-- 
2.31.1

[PATCH v2 3/4] block: rename IOPRIO_BE_NR

[Damien Le Moal]

The BFQ scheduler and ioprio_check_cap() both assume that the RT
priority class (IOPRIO_CLASS_RT) can have up to 8 different priority
levels. This is controlled using the macro IOPRIO_BE_NR, which is badly
named as the number of levels applies to the RT class.

Rename IOPRIO_BE_NR to the class independent IOPRIO_NR_LEVELS to make
things clear.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/bfq-iosched.c         | 8 ++++----
 block/bfq-iosched.h         | 4 ++--
 block/bfq-wf2q.c            | 6 +++---
 block/ioprio.c              | 3 +--
 fs/f2fs/sysfs.c             | 2 +-
 include/uapi/linux/ioprio.h | 4 ++--
 6 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 1f38d75524ae..d5824cab34d7 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2505,7 +2505,7 @@ void bfq_end_wr_async_queues(struct bfq_data *bfqd,
 	int i, j;
 
 	for (i = 0; i < 2; i++)
-		for (j = 0; j < IOPRIO_BE_NR; j++)
+		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
 			if (bfqg->async_bfqq[i][j])
 				bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
 	if (bfqg->async_idle_bfqq)
@@ -5290,10 +5290,10 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
 		break;
 	}
 
-	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
+	if (bfqq->new_ioprio >= IOPRIO_NR_LEVELS) {
 		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
 			bfqq->new_ioprio);
-		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
+		bfqq->new_ioprio = IOPRIO_NR_LEVELS - 1;
 	}
 
 	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
@@ -6822,7 +6822,7 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
 	int i, j;
 
 	for (i = 0; i < 2; i++)
-		for (j = 0; j < IOPRIO_BE_NR; j++)
+		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
 			__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
 
 	__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 99c2a3cb081e..385e28a843d1 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -931,7 +931,7 @@ struct bfq_group {
 
 	void *bfqd;
 
-	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
 	struct bfq_queue *async_idle_bfqq;
 
 	struct bfq_entity *my_entity;
@@ -948,7 +948,7 @@ struct bfq_group {
 	struct bfq_entity entity;
 	struct bfq_sched_data sched_data;
 
-	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
 	struct bfq_queue *async_idle_bfqq;
 
 	struct rb_root rq_pos_tree;
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 7a462df71f68..b74cc0da118e 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -505,7 +505,7 @@ static void bfq_active_insert(struct bfq_service_tree *st,
  */
 unsigned short bfq_ioprio_to_weight(int ioprio)
 {
-	return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
+	return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
 }
 
 /**
@@ -514,12 +514,12 @@ unsigned short bfq_ioprio_to_weight(int ioprio)
  *
  * To preserve as much as possible the old only-ioprio user interface,
  * 0 is used as an escape ioprio value for weights (numerically) equal or
- * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
+ * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
  */
 static unsigned short bfq_weight_to_ioprio(int weight)
 {
 	return max_t(int, 0,
-		     IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
+		     IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF - weight);
 }
 
 static void bfq_get_entity(struct bfq_entity *entity)
diff --git a/block/ioprio.c b/block/ioprio.c
index bee628f9f1b2..ca6b136c5586 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -74,9 +74,8 @@ int ioprio_check_cap(int ioprio)
 			fallthrough;
 			/* rt has prio field too */
 		case IOPRIO_CLASS_BE:
-			if (data >= IOPRIO_BE_NR || data < 0)
+			if (data >= IOPRIO_NR_LEVELS || data < 0)
 				return -EINVAL;
-
 			break;
 		case IOPRIO_CLASS_IDLE:
 			break;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 6642246206bd..daad532a4e2b 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -378,7 +378,7 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
 		ret = kstrtol(name, 10, &data);
 		if (ret)
 			return ret;
-		if (data >= IOPRIO_BE_NR || data < 0)
+		if (data >= IOPRIO_NR_LEVELS || data < 0)
 			return -EINVAL;
 
 		cprc->ckpt_thread_ioprio = IOPRIO_PRIO_VALUE(class, data);
diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index abc40965aa96..b9d48744dacb 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -31,9 +31,9 @@ enum {
 };
 
 /*
- * 8 best effort priority levels are supported
+ * The RT an BE priority classes support up to 8 priority levels.
  */
-#define IOPRIO_BE_NR	8
+#define IOPRIO_NR_LEVELS	8
 
 enum {
 	IOPRIO_WHO_PROCESS = 1,
-- 
2.31.1

[PATCH v2 4/4] block: fix default IO priority handling

[Damien Le Moal]

The default IO priority is the best effort (BE) class with the
normal priority level IOPRIO_NORM (4). However, get_task_ioprio()
returns IOPRIO_CLASS_NONE/IOPRIO_NORM as the default priority and
get_current_ioprio() returns IOPRIO_CLASS_NONE/0. Let's be consistent
with the defined default and have both of these functions return the
default priority IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM) when
the user did not define another default IO priority for the task.

In include/linux/ioprio.h, rename the IOPRIO_NORM macro to
IOPRIO_BE_NORM to clarify that this default level applies to the BE
priotity class. Also, define the macro IOPRIO_DEFAULT as
IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM) and use this new
macro when setting a priority to the default.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/bfq-iosched.c          | 2 +-
 block/ioprio.c               | 6 +++---
 drivers/nvme/host/lightnvm.c | 2 +-
 include/linux/ioprio.h       | 7 ++++++-
 include/uapi/linux/ioprio.h  | 4 ++--
 5 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index d5824cab34d7..a07d630c6972 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5408,7 +5408,7 @@ static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
 	case IOPRIO_CLASS_RT:
 		return &bfqg->async_bfqq[0][ioprio];
 	case IOPRIO_CLASS_NONE:
-		ioprio = IOPRIO_NORM;
+		ioprio = IOPRIO_BE_NORM;
 		fallthrough;
 	case IOPRIO_CLASS_BE:
 		return &bfqg->async_bfqq[1][ioprio];
diff --git a/block/ioprio.c b/block/ioprio.c
index ca6b136c5586..0e4ff245f2bf 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -170,7 +170,7 @@ 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_DEFAULT;
 	task_lock(p);
 	if (p->io_context)
 		ret = p->io_context->ioprio;
@@ -182,9 +182,9 @@ static int get_task_ioprio(struct task_struct *p)
 int ioprio_best(unsigned short aprio, unsigned short bprio)
 {
 	if (!ioprio_valid(aprio))
-		aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
+		aprio = IOPRIO_DEFAULT;
 	if (!ioprio_valid(bprio))
-		bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
+		bprio = IOPRIO_DEFAULT;
 
 	return min(aprio, bprio);
 }
diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
index e9d9ad47f70f..0fbbff0b3edb 100644
--- a/drivers/nvme/host/lightnvm.c
+++ b/drivers/nvme/host/lightnvm.c
@@ -662,7 +662,7 @@ static struct request *nvme_nvm_alloc_request(struct request_queue *q,
 	if (rqd->bio)
 		blk_rq_append_bio(rq, rqd->bio);
 	else
-		rq->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
+		rq->ioprio = IOPRIO_DEFAULT;
 
 	return rq;
 }
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 9b3a6d8172b4..2837c3a0d2e1 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -8,6 +8,11 @@
 
 #include <uapi/linux/ioprio.h>
 
+/*
+ * Default IO priority.
+ */
+#define IOPRIO_DEFAULT	IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM)
+
 /*
  * Check that a priority value has a valid class.
  */
@@ -50,7 +55,7 @@ static inline int get_current_ioprio(void)
 
 	if (ioc)
 		return ioc->ioprio;
-	return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+	return IOPRIO_DEFAULT;
 }
 
 /*
diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index b9d48744dacb..ccc633af44d5 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -42,8 +42,8 @@ enum {
 };
 
 /*
- * Fallback BE priority
+ * Fallback BE priority level.
  */
-#define IOPRIO_NORM	4
+#define IOPRIO_BE_NORM	4
 
 #endif /* _UAPI_LINUX_IOPRIO_H */
-- 
2.31.1

Re: [PATCH v2 1/4] block: bfq: fix bfq_set_next_ioprio_data()

[Hannes Reinecke]

On 8/6/21 7:11 AM, Damien Le Moal wrote:
> For a request that has a priority level equal to or larger than
> IOPRIO_BE_NR, bfq_set_next_ioprio_data() prints a critical warning but
> defaults to setting the request new_ioprio field to IOPRIO_BE_NR. This
> is not consistent with the warning and the allowed values for priority
> levels. Fix this by setting the request new_ioprio field to
> IOPRIO_BE_NR - 1, the lowest priority level allowed.
> 
> Cc: <stable@vger.kernel.org>
> Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   block/bfq-iosched.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH v2 2/4] block: fix ioprio interface

[Hannes Reinecke]

On 8/6/21 7:11 AM, Damien Le Moal wrote:
> An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
> in the block layer. E.g. ioprio_check_cap() takes an int as argument.
> With such implicit int casting function calls, the upper 16-bits of the
> int argument may be left uninitialized by the compiler, resulting in
> invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
> and in an error return for functions such as ioprio_check_cap().
> 
> Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
> in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
> defines the 3-bits mask for the priority class.
> 
> While at it, cleanup the following:
> * Apply the mask IOPRIO_PRIO_MASK to the data argument of the
>    IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
> * Remove unnecessary parenthesis around fixed values in the macro
>    definitions in include/uapi/linux/ioprio.h.
> * Update the outdated mention of CFQ in the comment describing priority
>    classes and instead mention BFQ and mq-deadline.
> * Change the argument name of the IOPRIO_PRIO_CLASS() and
>    IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
>    that an IO priority value should be passed rather than a mask.
> * Change the ioprio_valid() macro into an inline function, adding a
>    check on the maximum value of the class of a priority value as
>    defined by the IOPRIO_CLASS_MAX enum value. Move this function to
>    the kernel side in include/linux/ioprio.h.
> * Remove the unnecessary "else" after the return statements in
>    task_nice_ioclass().
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   include/linux/ioprio.h      | 15 ++++++++++++---
>   include/uapi/linux/ioprio.h | 19 +++++++++++--------
>   2 files changed, 23 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
> index ef9ad4fb245f..9b3a6d8172b4 100644
> --- a/include/linux/ioprio.h
> +++ b/include/linux/ioprio.h
> @@ -8,6 +8,16 @@
>   
>   #include <uapi/linux/ioprio.h>
>   
> +/*
> + * Check that a priority value has a valid class.
> + */
> +static inline bool ioprio_valid(unsigned short ioprio)

Wouldn't it be better to use 'u16' here as type, as we're relying on the 
number of bits?

> +{
> +	unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
> +
> +	return class > IOPRIO_CLASS_NONE && class < IOPRIO_CLASS_MAX;
> +}
> +
>   /*
>    * if process has set io priority explicitly, use that. if not, convert
>    * the cpu scheduler nice value to an io priority
> @@ -25,10 +35,9 @@ static inline int task_nice_ioclass(struct task_struct *task)
>   {
>   	if (task->policy == SCHED_IDLE)
>   		return IOPRIO_CLASS_IDLE;
> -	else if (task_is_realtime(task))
> +	if (task_is_realtime(task))
>   		return IOPRIO_CLASS_RT;
> -	else
> -		return IOPRIO_CLASS_BE;
> +	return IOPRIO_CLASS_BE;
>   }
>   
>   /*
> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
> index 77b17e08b0da..abc40965aa96 100644
> --- a/include/uapi/linux/ioprio.h
> +++ b/include/uapi/linux/ioprio.h
> @@ -5,12 +5,15 @@
>   /*
>    * Gives us 8 prio classes with 13-bits of data for each class
>    */
> -#define IOPRIO_CLASS_SHIFT	(13)
> +#define IOPRIO_CLASS_SHIFT	13
> +#define IOPRIO_CLASS_MASK	0x07
>   #define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
>   
> -#define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
> -#define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
> -#define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)
> +#define IOPRIO_PRIO_CLASS(ioprio)	\
> +	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
> +#define IOPRIO_PRIO_DATA(ioprio)	((ioprio) & IOPRIO_PRIO_MASK)
> +#define IOPRIO_PRIO_VALUE(class, data)	\
> +	(((class) << IOPRIO_CLASS_SHIFT) | ((data) & IOPRIO_PRIO_MASK))
>   
>   /*
>    * These are the io priority groups as implemented by CFQ. RT is the realtime
> @@ -23,14 +26,14 @@ enum {
>   	IOPRIO_CLASS_RT,
>   	IOPRIO_CLASS_BE,
>   	IOPRIO_CLASS_IDLE,
> -};
>   
> -#define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
> +	IOPRIO_CLASS_MAX,
> +};
>   
>   /*
>    * 8 best effort priority levels are supported
>    */
> -#define IOPRIO_BE_NR	(8)
> +#define IOPRIO_BE_NR	8
>   
>   enum {
>   	IOPRIO_WHO_PROCESS = 1,
> @@ -41,6 +44,6 @@ enum {
>   /*
>    * Fallback BE prioritye@su
>    */
> -#define IOPRIO_NORM	(4)
> +#define IOPRIO_NORM	4
>   
>   #endif /* _UAPI_LINUX_IOPRIO_H */
> 
Other than that:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH v2 3/4] block: rename IOPRIO_BE_NR

[Hannes Reinecke]

On 8/6/21 7:11 AM, Damien Le Moal wrote:
> The BFQ scheduler and ioprio_check_cap() both assume that the RT
> priority class (IOPRIO_CLASS_RT) can have up to 8 different priority
> levels. This is controlled using the macro IOPRIO_BE_NR, which is badly
> named as the number of levels applies to the RT class.
> 
> Rename IOPRIO_BE_NR to the class independent IOPRIO_NR_LEVELS to make
> things clear.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   block/bfq-iosched.c         | 8 ++++----
>   block/bfq-iosched.h         | 4 ++--
>   block/bfq-wf2q.c            | 6 +++---
>   block/ioprio.c              | 3 +--
>   fs/f2fs/sysfs.c             | 2 +-
>   include/uapi/linux/ioprio.h | 4 ++--
>   6 files changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 1f38d75524ae..d5824cab34d7 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -2505,7 +2505,7 @@ void bfq_end_wr_async_queues(struct bfq_data *bfqd,
>   	int i, j;
>   
>   	for (i = 0; i < 2; i++)
> -		for (j = 0; j < IOPRIO_BE_NR; j++)
> +		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
>   			if (bfqg->async_bfqq[i][j])
>   				bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
>   	if (bfqg->async_idle_bfqq)
> @@ -5290,10 +5290,10 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
>   		break;
>   	}
>   
> -	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
> +	if (bfqq->new_ioprio >= IOPRIO_NR_LEVELS) {
>   		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
>   			bfqq->new_ioprio);
> -		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
> +		bfqq->new_ioprio = IOPRIO_NR_LEVELS - 1;
>   	}
>   
>   	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
> @@ -6822,7 +6822,7 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
>   	int i, j;
>   
>   	for (i = 0; i < 2; i++)
> -		for (j = 0; j < IOPRIO_BE_NR; j++)
> +		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
>   			__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
>   
>   	__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 99c2a3cb081e..385e28a843d1 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -931,7 +931,7 @@ struct bfq_group {
>   
>   	void *bfqd;
>   
> -	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
> +	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
>   	struct bfq_queue *async_idle_bfqq;
>   
>   	struct bfq_entity *my_entity;
> @@ -948,7 +948,7 @@ struct bfq_group {
>   	struct bfq_entity entity;
>   	struct bfq_sched_data sched_data;
>   
> -	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
> +	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
>   	struct bfq_queue *async_idle_bfqq;
>   
>   	struct rb_root rq_pos_tree;
> diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
> index 7a462df71f68..b74cc0da118e 100644
> --- a/block/bfq-wf2q.c
> +++ b/block/bfq-wf2q.c
> @@ -505,7 +505,7 @@ static void bfq_active_insert(struct bfq_service_tree *st,
>    */
>   unsigned short bfq_ioprio_to_weight(int ioprio)
>   {
> -	return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
> +	return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
>   }
>   
>   /**
> @@ -514,12 +514,12 @@ unsigned short bfq_ioprio_to_weight(int ioprio)
>    *
>    * To preserve as much as possible the old only-ioprio user interface,
>    * 0 is used as an escape ioprio value for weights (numerically) equal or
> - * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
> + * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
>    */
>   static unsigned short bfq_weight_to_ioprio(int weight)
>   {
>   	return max_t(int, 0,
> -		     IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
> +		     IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF - weight);
>   }
>   
>   static void bfq_get_entity(struct bfq_entity *entity)
> diff --git a/block/ioprio.c b/block/ioprio.c
> index bee628f9f1b2..ca6b136c5586 100644
> --- a/block/ioprio.c
> +++ b/block/ioprio.c
> @@ -74,9 +74,8 @@ int ioprio_check_cap(int ioprio)
>   			fallthrough;
>   			/* rt has prio field too */
>   		case IOPRIO_CLASS_BE:
> -			if (data >= IOPRIO_BE_NR || data < 0)
> +			if (data >= IOPRIO_NR_LEVELS || data < 0)
>   				return -EINVAL;
> -
>   			break;
>   		case IOPRIO_CLASS_IDLE:
>   			break;
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 6642246206bd..daad532a4e2b 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -378,7 +378,7 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>   		ret = kstrtol(name, 10, &data);
>   		if (ret)
>   			return ret;
> -		if (data >= IOPRIO_BE_NR || data < 0)
> +		if (data >= IOPRIO_NR_LEVELS || data < 0)
>   			return -EINVAL;
>   
>   		cprc->ckpt_thread_ioprio = IOPRIO_PRIO_VALUE(class, data);
> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
> index abc40965aa96..b9d48744dacb 100644
> --- a/include/uapi/linux/ioprio.h
> +++ b/include/uapi/linux/ioprio.h
> @@ -31,9 +31,9 @@ enum {
>   };
>   
>   /*
> - * 8 best effort priority levels are supported
> + * The RT an BE priority classes support up to 8 priority levels.

This sentence no verb :-)
(maybe 'The RT class is an BE priority ...'?)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH v2 4/4] block: fix default IO priority handling

[Hannes Reinecke]

On 8/6/21 7:11 AM, Damien Le Moal wrote:
> The default IO priority is the best effort (BE) class with the
> normal priority level IOPRIO_NORM (4). However, get_task_ioprio()
> returns IOPRIO_CLASS_NONE/IOPRIO_NORM as the default priority and
> get_current_ioprio() returns IOPRIO_CLASS_NONE/0. Let's be consistent
> with the defined default and have both of these functions return the
> default priority IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM) when
> the user did not define another default IO priority for the task.
> 
> In include/linux/ioprio.h, rename the IOPRIO_NORM macro to
> IOPRIO_BE_NORM to clarify that this default level applies to the BE
> priotity class. Also, define the macro IOPRIO_DEFAULT as
> IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM) and use this new
> macro when setting a priority to the default.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   block/bfq-iosched.c          | 2 +-
>   block/ioprio.c               | 6 +++---
>   drivers/nvme/host/lightnvm.c | 2 +-
>   include/linux/ioprio.h       | 7 ++++++-
>   include/uapi/linux/ioprio.h  | 4 ++--
>   5 files changed, 13 insertions(+), 8 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH v2 3/4] block: rename IOPRIO_BE_NR

[Damien Le Moal]

On 2021/08/06 15:38, Hannes Reinecke wrote:
> On 8/6/21 7:11 AM, Damien Le Moal wrote:
>> The BFQ scheduler and ioprio_check_cap() both assume that the RT
>> priority class (IOPRIO_CLASS_RT) can have up to 8 different priority
>> levels. This is controlled using the macro IOPRIO_BE_NR, which is badly
>> named as the number of levels applies to the RT class.
>>
>> Rename IOPRIO_BE_NR to the class independent IOPRIO_NR_LEVELS to make
>> things clear.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>>   block/bfq-iosched.c         | 8 ++++----
>>   block/bfq-iosched.h         | 4 ++--
>>   block/bfq-wf2q.c            | 6 +++---
>>   block/ioprio.c              | 3 +--
>>   fs/f2fs/sysfs.c             | 2 +-
>>   include/uapi/linux/ioprio.h | 4 ++--
>>   6 files changed, 13 insertions(+), 14 deletions(-)
>>
>> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
>> index 1f38d75524ae..d5824cab34d7 100644
>> --- a/block/bfq-iosched.c
>> +++ b/block/bfq-iosched.c
>> @@ -2505,7 +2505,7 @@ void bfq_end_wr_async_queues(struct bfq_data *bfqd,
>>   	int i, j;
>>   
>>   	for (i = 0; i < 2; i++)
>> -		for (j = 0; j < IOPRIO_BE_NR; j++)
>> +		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
>>   			if (bfqg->async_bfqq[i][j])
>>   				bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
>>   	if (bfqg->async_idle_bfqq)
>> @@ -5290,10 +5290,10 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
>>   		break;
>>   	}
>>   
>> -	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
>> +	if (bfqq->new_ioprio >= IOPRIO_NR_LEVELS) {
>>   		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
>>   			bfqq->new_ioprio);
>> -		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
>> +		bfqq->new_ioprio = IOPRIO_NR_LEVELS - 1;
>>   	}
>>   
>>   	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
>> @@ -6822,7 +6822,7 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
>>   	int i, j;
>>   
>>   	for (i = 0; i < 2; i++)
>> -		for (j = 0; j < IOPRIO_BE_NR; j++)
>> +		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
>>   			__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
>>   
>>   	__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
>> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
>> index 99c2a3cb081e..385e28a843d1 100644
>> --- a/block/bfq-iosched.h
>> +++ b/block/bfq-iosched.h
>> @@ -931,7 +931,7 @@ struct bfq_group {
>>   
>>   	void *bfqd;
>>   
>> -	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
>> +	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
>>   	struct bfq_queue *async_idle_bfqq;
>>   
>>   	struct bfq_entity *my_entity;
>> @@ -948,7 +948,7 @@ struct bfq_group {
>>   	struct bfq_entity entity;
>>   	struct bfq_sched_data sched_data;
>>   
>> -	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
>> +	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
>>   	struct bfq_queue *async_idle_bfqq;
>>   
>>   	struct rb_root rq_pos_tree;
>> diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
>> index 7a462df71f68..b74cc0da118e 100644
>> --- a/block/bfq-wf2q.c
>> +++ b/block/bfq-wf2q.c
>> @@ -505,7 +505,7 @@ static void bfq_active_insert(struct bfq_service_tree *st,
>>    */
>>   unsigned short bfq_ioprio_to_weight(int ioprio)
>>   {
>> -	return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
>> +	return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
>>   }
>>   
>>   /**
>> @@ -514,12 +514,12 @@ unsigned short bfq_ioprio_to_weight(int ioprio)
>>    *
>>    * To preserve as much as possible the old only-ioprio user interface,
>>    * 0 is used as an escape ioprio value for weights (numerically) equal or
>> - * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
>> + * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
>>    */
>>   static unsigned short bfq_weight_to_ioprio(int weight)
>>   {
>>   	return max_t(int, 0,
>> -		     IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
>> +		     IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF - weight);
>>   }
>>   
>>   static void bfq_get_entity(struct bfq_entity *entity)
>> diff --git a/block/ioprio.c b/block/ioprio.c
>> index bee628f9f1b2..ca6b136c5586 100644
>> --- a/block/ioprio.c
>> +++ b/block/ioprio.c
>> @@ -74,9 +74,8 @@ int ioprio_check_cap(int ioprio)
>>   			fallthrough;
>>   			/* rt has prio field too */
>>   		case IOPRIO_CLASS_BE:
>> -			if (data >= IOPRIO_BE_NR || data < 0)
>> +			if (data >= IOPRIO_NR_LEVELS || data < 0)
>>   				return -EINVAL;
>> -
>>   			break;
>>   		case IOPRIO_CLASS_IDLE:
>>   			break;
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index 6642246206bd..daad532a4e2b 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -378,7 +378,7 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>>   		ret = kstrtol(name, 10, &data);
>>   		if (ret)
>>   			return ret;
>> -		if (data >= IOPRIO_BE_NR || data < 0)
>> +		if (data >= IOPRIO_NR_LEVELS || data < 0)
>>   			return -EINVAL;
>>   
>>   		cprc->ckpt_thread_ioprio = IOPRIO_PRIO_VALUE(class, data);
>> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
>> index abc40965aa96..b9d48744dacb 100644
>> --- a/include/uapi/linux/ioprio.h
>> +++ b/include/uapi/linux/ioprio.h
>> @@ -31,9 +31,9 @@ enum {
>>   };
>>   
>>   /*
>> - * 8 best effort priority levels are supported
>> + * The RT an BE priority classes support up to 8 priority levels.
> 
> This sentence no verb :-)

Hu ? "support" is a verb (to support). It is a noun too, but here, I use the verb :)

There is a typo though: s/an/and

"The RT and BE priority classes support up to 8 priority levels."

Arg... Sending v3 :)

> (maybe 'The RT class is an BE priority ...'?)
> 
> Cheers,
> 
> Hannes
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 2/4] block: fix ioprio interface

[Damien Le Moal]

On 2021/08/06 15:35, Hannes Reinecke wrote:
> On 8/6/21 7:11 AM, Damien Le Moal wrote:
>> An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
>> in the block layer. E.g. ioprio_check_cap() takes an int as argument.
>> With such implicit int casting function calls, the upper 16-bits of the
>> int argument may be left uninitialized by the compiler, resulting in
>> invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
>> and in an error return for functions such as ioprio_check_cap().
>>
>> Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
>> in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
>> defines the 3-bits mask for the priority class.
>>
>> While at it, cleanup the following:
>> * Apply the mask IOPRIO_PRIO_MASK to the data argument of the
>>    IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
>> * Remove unnecessary parenthesis around fixed values in the macro
>>    definitions in include/uapi/linux/ioprio.h.
>> * Update the outdated mention of CFQ in the comment describing priority
>>    classes and instead mention BFQ and mq-deadline.
>> * Change the argument name of the IOPRIO_PRIO_CLASS() and
>>    IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
>>    that an IO priority value should be passed rather than a mask.
>> * Change the ioprio_valid() macro into an inline function, adding a
>>    check on the maximum value of the class of a priority value as
>>    defined by the IOPRIO_CLASS_MAX enum value. Move this function to
>>    the kernel side in include/linux/ioprio.h.
>> * Remove the unnecessary "else" after the return statements in
>>    task_nice_ioclass().
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>>   include/linux/ioprio.h      | 15 ++++++++++++---
>>   include/uapi/linux/ioprio.h | 19 +++++++++++--------
>>   2 files changed, 23 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
>> index ef9ad4fb245f..9b3a6d8172b4 100644
>> --- a/include/linux/ioprio.h
>> +++ b/include/linux/ioprio.h
>> @@ -8,6 +8,16 @@
>>   
>>   #include <uapi/linux/ioprio.h>
>>   
>> +/*
>> + * Check that a priority value has a valid class.
>> + */
>> +static inline bool ioprio_valid(unsigned short ioprio)
> 
> Wouldn't it be better to use 'u16' here as type, as we're relying on the 
> number of bits?

Other functions in block/ioprio.c and in include/linux/ioprio.h use "unsigned
short", so I followed. But many functions, if not most, use "int". This is all a
bit of a mess. I think we need a "typedef ioprio_t u16;" to clean things up. But
there are a lot of places to fix. I can add such patch... Worth it ?

> 
>> +{
>> +	unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
>> +
>> +	return class > IOPRIO_CLASS_NONE && class < IOPRIO_CLASS_MAX;
>> +}
>> +
>>   /*
>>    * if process has set io priority explicitly, use that. if not, convert
>>    * the cpu scheduler nice value to an io priority
>> @@ -25,10 +35,9 @@ static inline int task_nice_ioclass(struct task_struct *task)
>>   {
>>   	if (task->policy == SCHED_IDLE)
>>   		return IOPRIO_CLASS_IDLE;
>> -	else if (task_is_realtime(task))
>> +	if (task_is_realtime(task))
>>   		return IOPRIO_CLASS_RT;
>> -	else
>> -		return IOPRIO_CLASS_BE;
>> +	return IOPRIO_CLASS_BE;
>>   }
>>   
>>   /*
>> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
>> index 77b17e08b0da..abc40965aa96 100644
>> --- a/include/uapi/linux/ioprio.h
>> +++ b/include/uapi/linux/ioprio.h
>> @@ -5,12 +5,15 @@
>>   /*
>>    * Gives us 8 prio classes with 13-bits of data for each class
>>    */
>> -#define IOPRIO_CLASS_SHIFT	(13)
>> +#define IOPRIO_CLASS_SHIFT	13
>> +#define IOPRIO_CLASS_MASK	0x07
>>   #define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)
>>   
>> -#define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
>> -#define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
>> -#define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)
>> +#define IOPRIO_PRIO_CLASS(ioprio)	\
>> +	(((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
>> +#define IOPRIO_PRIO_DATA(ioprio)	((ioprio) & IOPRIO_PRIO_MASK)
>> +#define IOPRIO_PRIO_VALUE(class, data)	\
>> +	(((class) << IOPRIO_CLASS_SHIFT) | ((data) & IOPRIO_PRIO_MASK))
>>   
>>   /*
>>    * These are the io priority groups as implemented by CFQ. RT is the realtime
>> @@ -23,14 +26,14 @@ enum {
>>   	IOPRIO_CLASS_RT,
>>   	IOPRIO_CLASS_BE,
>>   	IOPRIO_CLASS_IDLE,
>> -};
>>   
>> -#define ioprio_valid(mask)	(IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
>> +	IOPRIO_CLASS_MAX,
>> +};
>>   
>>   /*
>>    * 8 best effort priority levels are supported
>>    */
>> -#define IOPRIO_BE_NR	(8)
>> +#define IOPRIO_BE_NR	8
>>   
>>   enum {
>>   	IOPRIO_WHO_PROCESS = 1,
>> @@ -41,6 +44,6 @@ enum {
>>   /*
>>    * Fallback BE prioritye@su
>>    */
>> -#define IOPRIO_NORM	(4)
>> +#define IOPRIO_NORM	4
>>   
>>   #endif /* _UAPI_LINUX_IOPRIO_H */
>>
> Other than that:
> 
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> 
> Cheers,
> 
> Hannes
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 2/4] block: fix ioprio interface

[Hannes Reinecke]

On 8/6/21 8:57 AM, Damien Le Moal wrote:
> On 2021/08/06 15:35, Hannes Reinecke wrote:
>> On 8/6/21 7:11 AM, Damien Le Moal wrote:
>>> An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
>>> in the block layer. E.g. ioprio_check_cap() takes an int as argument.
>>> With such implicit int casting function calls, the upper 16-bits of the
>>> int argument may be left uninitialized by the compiler, resulting in
>>> invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
>>> and in an error return for functions such as ioprio_check_cap().
>>>
>>> Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
>>> in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
>>> defines the 3-bits mask for the priority class.
>>>
>>> While at it, cleanup the following:
>>> * Apply the mask IOPRIO_PRIO_MASK to the data argument of the
>>>    IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
>>> * Remove unnecessary parenthesis around fixed values in the macro
>>>    definitions in include/uapi/linux/ioprio.h.
>>> * Update the outdated mention of CFQ in the comment describing priority
>>>    classes and instead mention BFQ and mq-deadline.
>>> * Change the argument name of the IOPRIO_PRIO_CLASS() and
>>>    IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
>>>    that an IO priority value should be passed rather than a mask.
>>> * Change the ioprio_valid() macro into an inline function, adding a
>>>    check on the maximum value of the class of a priority value as
>>>    defined by the IOPRIO_CLASS_MAX enum value. Move this function to
>>>    the kernel side in include/linux/ioprio.h.
>>> * Remove the unnecessary "else" after the return statements in
>>>    task_nice_ioclass().
>>>
>>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>>> ---
>>>   include/linux/ioprio.h      | 15 ++++++++++++---
>>>   include/uapi/linux/ioprio.h | 19 +++++++++++--------
>>>   2 files changed, 23 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
>>> index ef9ad4fb245f..9b3a6d8172b4 100644
>>> --- a/include/linux/ioprio.h
>>> +++ b/include/linux/ioprio.h
>>> @@ -8,6 +8,16 @@
>>>   
>>>   #include <uapi/linux/ioprio.h>
>>>   
>>> +/*
>>> + * Check that a priority value has a valid class.
>>> + */
>>> +static inline bool ioprio_valid(unsigned short ioprio)
>>
>> Wouldn't it be better to use 'u16' here as type, as we're relying on the 
>> number of bits?
> 
> Other functions in block/ioprio.c and in include/linux/ioprio.h use "unsigned
> short", so I followed. But many functions, if not most, use "int". This is all a
> bit of a mess. I think we need a "typedef ioprio_t u16;" to clean things up. But
> there are a lot of places to fix. I can add such patch... Worth it ?
> 
Possibly not.
Consider my comment retracted :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
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