[PATCH v4 0/3] AIO add per-command iopriority

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.
See the following link for performance implications on a SATA HDD:
https://lkml.org/lkml/2016/12/6/495

First patch factors ioprio_check_cap function out of ioprio_set system call to
also be used by the aio ioprio interface.

Second patch converts kiocb ki_hint field to a u16 to avoid kiocb bloat.

Third patch passes ioprio hint from aio iocb to kiocb and enables block_dev
usage of the per I/O ioprio feature.

v2: merge patches
    use IOCB_FLAG_IOPRIO
    validate intended use with IOCB_IOPRIO
    add linux-api and linux-block to cc

v3: add ioprio_check_cap function
    convert kiocb ki_hint to u16
    use ioprio_check_cap when adding ioprio to kiocb in aio.c

v4: handle IOCB_IOPRIO in aio_prep_rw
    note patch 3 depends on patch 1 in commit msg

Adam Manzanares (3):
  block: add ioprio_check_cap function
  fs: Convert kiocb rw_hint from enum to u16
  fs: Add aio iopriority support for block_dev

 block/ioprio.c               | 22 ++++++++++++++++------
 fs/aio.c                     | 16 ++++++++++++++++
 fs/block_dev.c               |  2 ++
 include/linux/fs.h           | 17 +++++++++++++++--
 include/linux/ioprio.h       |  2 ++
 include/uapi/linux/aio_abi.h |  1 +
 6 files changed, 52 insertions(+), 8 deletions(-)

-- 
2.15.1

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From: Adam Manzanares <redacted>

Aio per command iopriority support introduces a second interface between
userland and the kernel capable of passing iopriority. The aio interface also
needs the ability to verify that the submitting context has sufficient
priviledges to submit IOPRIO_RT commands. This patch creates the
ioprio_check_cap function to be used by the ioprio_set system call and also by
the aio interface.

Signed-off-by: Adam Manzanares <redacted>
---
 block/ioprio.c         | 22 ++++++++++++++++------
 include/linux/ioprio.h |  2 ++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 6f5d0b6625e3..f9821080c92c 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c

@@ -61,15 +61,10 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
 }
 EXPORT_SYMBOL_GPL(set_task_ioprio);
 
-SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+int ioprio_check_cap(int ioprio)
 {
 	int class = IOPRIO_PRIO_CLASS(ioprio);
 	int data = IOPRIO_PRIO_DATA(ioprio);
-	struct task_struct *p, *g;
-	struct user_struct *user;
-	struct pid *pgrp;
-	kuid_t uid;
-	int ret;
 
 	switch (class) {
 		case IOPRIO_CLASS_RT:

@@ -92,6 +87,21 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
 			return -EINVAL;
 	}
 
+	return 0;
+}
+
+SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+{
+	struct task_struct *p, *g;
+	struct user_struct *user;
+	struct pid *pgrp;
+	kuid_t uid;
+	int ret;
+
+	ret = ioprio_check_cap(ioprio);
+	if (ret)
+		return ret;
+
 	ret = -ESRCH;
 	rcu_read_lock();
 	switch (which) {

diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 627efac73e6d..4a28cec49ec3 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h

@@ -77,4 +77,6 @@ extern int ioprio_best(unsigned short aprio, unsigned short bprio);
 
 extern int set_task_ioprio(struct task_struct *task, int ioprio);
 
+extern int ioprio_check_cap(int ioprio);
+
 #endif

-- 
2.15.1

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From: Adam Manzanares <redacted>

In order to avoid kiocb bloat for per command iopriority support, rw_hint
is converted from enum to a u16. Added a guard around ki_hint assigment.

Signed-off-by: Adam Manzanares <redacted>
---
 include/linux/fs.h | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 760d8da1b6c7..7a90ce387e00 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h

@@ -284,6 +284,8 @@ enum rw_hint {
 	WRITE_LIFE_EXTREME	= RWH_WRITE_LIFE_EXTREME,
 };
 
+#define MAX_KI_HINT		((1 << 16) - 1) /* ki_hint type is u16 */
+
 #define IOCB_EVENTFD		(1 << 0)
 #define IOCB_APPEND		(1 << 1)
 #define IOCB_DIRECT		(1 << 2)

@@ -299,7 +301,7 @@ struct kiocb {
 	void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
 	void			*private;
 	int			ki_flags;
-	enum rw_hint		ki_hint;
+	u16			ki_hint;
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)

@@ -1927,12 +1929,21 @@ static inline enum rw_hint file_write_hint(struct file *file)
 
 static inline int iocb_flags(struct file *file);
 
+/* ki_hint changed from enum to u16, make sure rw_hint fits into u16 */
+static inline u16 ki_hint_valid(enum rw_hint hint)
+{
+	if (hint > MAX_KI_HINT)
+		return 0;
+
+	return hint;
+}
+
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
 	*kiocb = (struct kiocb) {
 		.ki_filp = filp,
 		.ki_flags = iocb_flags(filp),
-		.ki_hint = file_write_hint(filp),
+		.ki_hint = ki_hint_valid(file_write_hint(filp)),
 	};
 }
 

-- 
2.15.1

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From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

When a bio is created for an aio request by the block dev we set the priority
value of the bio to the user supplied value.

This patch depends on block: add ioprio_check_cap function

Signed-off-by: Adam Manzanares <redacted>
---
 fs/aio.c                     | 16 ++++++++++++++++
 fs/block_dev.c               |  2 ++
 include/linux/fs.h           |  2 ++
 include/uapi/linux/aio_abi.h |  1 +
 4 files changed, 21 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index f3eae5d5771b..ff3107aa82d5 100644
--- a/fs/aio.c
+++ b/fs/aio.c

@@ -1451,6 +1451,22 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
 	if (iocb->aio_flags & IOCB_FLAG_RESFD)
 		req->ki_flags |= IOCB_EVENTFD;
 	req->ki_hint = file_write_hint(req->ki_filp);
+	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
+		/*
+		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
+		 * aio_reqprio is interpreted as an I/O scheduling
+		 * class and priority.
+		 */
+		ret = ioprio_check_cap(iocb->aio_reqprio);
+		if (ret) {
+			pr_debug("aio ioprio check cap error\n");
+			return -EINVAL;
+		}
+
+		req->ki_ioprio = iocb->aio_reqprio;
+		req->ki_flags |= IOCB_IOPRIO;
+	}
+
 	ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
 	if (unlikely(ret))
 		fput(req->ki_filp);

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7ec920e27065..970bef79caa6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c

@@ -355,6 +355,8 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 		bio->bi_write_hint = iocb->ki_hint;
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;
+		if (iocb->ki_flags & IOCB_IOPRIO)
+			bio->bi_ioprio = iocb->ki_ioprio;
 
 		ret = bio_iov_iter_get_pages(bio, iter);
 		if (unlikely(ret)) {

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7a90ce387e00..3415e83f6350 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h

@@ -294,6 +294,7 @@ enum rw_hint {
 #define IOCB_SYNC		(1 << 5)
 #define IOCB_WRITE		(1 << 6)
 #define IOCB_NOWAIT		(1 << 7)
+#define IOCB_IOPRIO		(1 << 8)
 
 struct kiocb {
 	struct file		*ki_filp;

@@ -302,6 +303,7 @@ struct kiocb {
 	void			*private;
 	int			ki_flags;
 	u16			ki_hint;
+	u16			ki_ioprio; /* See linux/ioprio.h */
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)

diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index 2c0a3415beee..d4e768d55d14 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h

@@ -55,6 +55,7 @@ enum {
  *                   is valid.
  */
 #define IOCB_FLAG_RESFD		(1 << 0)
+#define IOCB_FLAG_IOPRIO	(1 << 1)
 
 /* read() from /dev/aio returns these structures. */
 struct io_event {

-- 
2.15.1

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On 5/17/18 2:38 PM, adam.manzanares@wdc.com wrote:

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.
See the following link for performance implications on a SATA HDD:
https://lkml.org/lkml/2016/12/6/495

First patch factors ioprio_check_cap function out of ioprio_set system call to
also be used by the aio ioprio interface.

Second patch converts kiocb ki_hint field to a u16 to avoid kiocb bloat.

Third patch passes ioprio hint from aio iocb to kiocb and enables block_dev
usage of the per I/O ioprio feature.

v2: merge patches
    use IOCB_FLAG_IOPRIO
    validate intended use with IOCB_IOPRIO
    add linux-api and linux-block to cc

v3: add ioprio_check_cap function
    convert kiocb ki_hint to u16
    use ioprio_check_cap when adding ioprio to kiocb in aio.c

v4: handle IOCB_IOPRIO in aio_prep_rw
    note patch 3 depends on patch 1 in commit msg

Adam Manzanares (3):
  block: add ioprio_check_cap function
  fs: Convert kiocb rw_hint from enum to u16
  fs: Add aio iopriority support for block_dev

 block/ioprio.c               | 22 ++++++++++++++++------
 fs/aio.c                     | 16 ++++++++++++++++
 fs/block_dev.c               |  2 ++
 include/linux/fs.h           | 17 +++++++++++++++--
 include/linux/ioprio.h       |  2 ++
 include/uapi/linux/aio_abi.h |  1 +
 6 files changed, 52 insertions(+), 8 deletions(-)

This looks fine to me now. I can pick up #1 for 4.18 - and 2+3 as well,
unless someone else wants to take them.

-- 
Jens Axboe

On 5/17/18 7:41 PM, Jens Axboe wrote:

On 5/17/18 2:38 PM, adam.manzanares@wdc.com wrote:

quoted

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.
See the following link for performance implications on a SATA HDD:
https://lkml.org/lkml/2016/12/6/495

First patch factors ioprio_check_cap function out of ioprio_set system call to
also be used by the aio ioprio interface.

Second patch converts kiocb ki_hint field to a u16 to avoid kiocb bloat.

Third patch passes ioprio hint from aio iocb to kiocb and enables block_dev
usage of the per I/O ioprio feature.

v2: merge patches
     use IOCB_FLAG_IOPRIO
     validate intended use with IOCB_IOPRIO
     add linux-api and linux-block to cc

v3: add ioprio_check_cap function
     convert kiocb ki_hint to u16
     use ioprio_check_cap when adding ioprio to kiocb in aio.c

v4: handle IOCB_IOPRIO in aio_prep_rw
     note patch 3 depends on patch 1 in commit msg

Adam Manzanares (3):
   block: add ioprio_check_cap function
   fs: Convert kiocb rw_hint from enum to u16
   fs: Add aio iopriority support for block_dev

  block/ioprio.c               | 22 ++++++++++++++++------
  fs/aio.c                     | 16 ++++++++++++++++
  fs/block_dev.c               |  2 ++
  include/linux/fs.h           | 17 +++++++++++++++--
  include/linux/ioprio.h       |  2 ++
  include/uapi/linux/aio_abi.h |  1 +
  6 files changed, 52 insertions(+), 8 deletions(-)

This looks fine to me now. I can pick up #1 for 4.18 - and 2+3 as well,
unless someone else wants to take them.

Great, thanks Jens.

On 5/17/18 2:38 PM, adam.manzanares@wdc.com wrote:

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

When a bio is created for an aio request by the block dev we set the priority
value of the bio to the user supplied value.

This patch depends on block: add ioprio_check_cap function

Actually, one comment on this one:

Do we really need IOCB_IOPRIO? All zeroes is no priority set anyway,
so we should be able to get by with just setting ->ki_ioprio to either
the priority, or 0.

And then this assignment can just happen unconditionally.

-- 
Jens Axboe

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On 5/18/18 8:14 AM, Jens Axboe wrote:

On 5/17/18 2:38 PM, adam.manzanares@wdc.com wrote:

quoted

From: Adam Manzanares <redacted>

This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

When a bio is created for an aio request by the block dev we set the priority
value of the bio to the user supplied value.

This patch depends on block: add ioprio_check_cap function

Actually, one comment on this one:

quoted

diff --git a/fs/aio.c b/fs/aio.c
index f3eae5d5771b..ff3107aa82d5 100644
--- a/fs/aio.c
+++ b/fs/aio.c

@@ -1451,6 +1451,22 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
  	if (iocb->aio_flags & IOCB_FLAG_RESFD)
  		req->ki_flags |= IOCB_EVENTFD;
  	req->ki_hint = file_write_hint(req->ki_filp);
+	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
+		/*
+		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
+		 * aio_reqprio is interpreted as an I/O scheduling
+		 * class and priority.
+		 */
+		ret = ioprio_check_cap(iocb->aio_reqprio);
+		if (ret) {
+			pr_debug("aio ioprio check cap error\n");
+			return -EINVAL;
+		}
+
+		req->ki_ioprio = iocb->aio_reqprio;
+		req->ki_flags |= IOCB_IOPRIO;
+	}

Do we really need IOCB_IOPRIO? All zeroes is no priority set anyway,
so we should be able to get by with just setting ->ki_ioprio to either
the priority, or 0.

quoted

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7ec920e27065..970bef79caa6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c

@@ -355,6 +355,8 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
  		bio->bi_write_hint = iocb->ki_hint;
  		bio->bi_private = dio;
  		bio->bi_end_io = blkdev_bio_end_io;
+		if (iocb->ki_flags & IOCB_IOPRIO)
+			bio->bi_ioprio = iocb->ki_ioprio;

And then this assignment can just happen unconditionally.

That is a cleaner way of guaranteeing the ioprio set on the kiocb is 
only set when the user intends to use the ioprio from the iocb.

I'll resend the series.

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On Thu, May 17, 2018 at 01:38:01PM -0700, adam.manzanares@wdc.com wrote:

From: Adam Manzanares <redacted>

Aio per command iopriority support introduces a second interface between
userland and the kernel capable of passing iopriority. The aio interface also
needs the ability to verify that the submitting context has sufficient
priviledges to submit IOPRIO_RT commands. This patch creates the
ioprio_check_cap function to be used by the ioprio_set system call and also by
the aio interface.

Signed-off-by: Adam Manzanares <redacted>

Looks fine,

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

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+/* ki_hint changed from enum to u16, make sure rw_hint fits into u16 */

I don't think this comment is very useful.

+static inline u16 ki_hint_valid(enum rw_hint hint)

I'd call this ki_hint_validate.

+{
+	if (hint > MAX_KI_HINT)
+		return 0;
+
+	return hint;

Nit: kill the empty line.

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Looks fine, although I'd split it into a aio and block_dev patch.

Also please wire this up for the fs/iomap.c direct I/O code, it should
be essentially the same sniplet as in the block_dev.c code.

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On 5/18/18 9:05 AM, Christoph Hellwig wrote:

quoted

+/* ki_hint changed from enum to u16, make sure rw_hint fits into u16 */

I don't think this comment is very useful.

quoted

+static inline u16 ki_hint_valid(enum rw_hint hint)

I'd call this ki_hint_validate.

quoted

+{
+	if (hint > MAX_KI_HINT)
+		return 0;
+
+	return hint;

Nit: kill the empty line.

I'll clean this up in the next revision.

On 5/18/18 9:06 AM, Christoph Hellwig wrote:

Looks fine, although I'd split it into a aio and block_dev patch.

Also please wire this up for the fs/iomap.c direct I/O code, it should
be essentially the same sniplet as in the block_dev.c code.

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Hi Adam,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on next-20180516]
[cannot apply to linus/master block/for-next v4.17-rc5 v4.17-rc4 v4.17-rc3 v4.17-rc5]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/adam-manzanares-wdc-com/AIO-add-per-command-iopriority/20180519-031848
config: x86_64-randconfig-x013-201819 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   fs/aio.c: In function 'aio_prep_rw':

quoted

fs/aio.c:1460:9: error: implicit declaration of function 'ioprio_check_cap'; did you mean 'param_check_charp'? [-Werror=implicit-function-declaration]

      ret = ioprio_check_cap(iocb->aio_reqprio);
            ^~~~~~~~~~~~~~~~
            param_check_charp
   cc1: some warnings being treated as errors

vim +1460 fs/aio.c

  1440	
  1441	static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
  1442	{
  1443		int ret;
  1444	
  1445		req->ki_filp = fget(iocb->aio_fildes);
  1446		if (unlikely(!req->ki_filp))
  1447			return -EBADF;
  1448		req->ki_complete = aio_complete_rw;
  1449		req->ki_pos = iocb->aio_offset;
  1450		req->ki_flags = iocb_flags(req->ki_filp);
  1451		if (iocb->aio_flags & IOCB_FLAG_RESFD)
  1452			req->ki_flags |= IOCB_EVENTFD;
  1453		req->ki_hint = file_write_hint(req->ki_filp);
  1454		if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
  1455			/*
  1456			 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
  1457			 * aio_reqprio is interpreted as an I/O scheduling
  1458			 * class and priority.
  1459			 */

1460			ret = ioprio_check_cap(iocb->aio_reqprio);

  1461			if (ret) {
  1462				pr_debug("aio ioprio check cap error\n");
  1463				return -EINVAL;
  1464			}
  1465	
  1466			req->ki_ioprio = iocb->aio_reqprio;
  1467			req->ki_flags |= IOCB_IOPRIO;
  1468		}
  1469	
  1470		ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
  1471		if (unlikely(ret))
  1472			fput(req->ki_filp);
  1473		return ret;
  1474	}
  1475	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation