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Subject[PATCH v5 3/5] fs: Add aio iopriority support
Date
From: Adam Manzanares <adam.manzanares@wdc.com>

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.

We set the blkdev bio iopriority unconditionally, so we need to guarantee the
kiocb is initialized properly. Added changes to the loopback driver and
init_sync_kiocb to achieve this.

This patch depends on block: add ioprio_check_cap function.

Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
---
drivers/block/loop.c | 3 +++
fs/aio.c | 16 ++++++++++++++++
include/linux/fs.h | 3 +++
include/uapi/linux/aio_abi.h | 1 +
4 files changed, 23 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5d4e31655d96..dd98dfd97f5e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -76,6 +76,8 @@
#include <linux/miscdevice.h>
#include <linux/falloc.h>
#include <linux/uio.h>
+#include <linux/ioprio.h>
+
#include "loop.h"

#include <linux/uaccess.h>
@@ -559,6 +561,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
cmd->iocb.ki_filp = file;
cmd->iocb.ki_complete = lo_rw_aio_complete;
cmd->iocb.ki_flags = IOCB_DIRECT;
+ cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
if (cmd->css)
kthread_associate_blkcg(cmd->css);

diff --git a/fs/aio.c b/fs/aio.c
index f3eae5d5771b..44b4572be524 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;
+ } else
+ req->ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+
ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
if (unlikely(ret))
fput(req->ki_filp);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 50de40dbbb85..73b749ed3ea1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -36,6 +36,7 @@
#include <linux/delayed_call.h>
#include <linux/uuid.h>
#include <linux/errseq.h>
+#include <linux/ioprio.h>

#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -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)
@@ -1942,6 +1944,7 @@ 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),
};
}

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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