linux-kernel - Re: [PATCH v5 3/5] fs: Add aio iopriority support

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Date:   Mon, 21 May 2018 16:58:39 -0400
From:   Jeff Moyer <jmoyer@...hat.com>
To:     adam.manzanares@....com
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        axboe@...nel.dk, bcrl@...ck.org, tglx@...utronix.de,
        mingo@...nel.org, pombredanne@...b.com,
        kstewart@...uxfoundation.org, gregkh@...uxfoundation.org,
        bigeasy@...utronix.de, jack@...e.cz, darrick.wong@...cle.com,
        rgoldwyn@...e.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-aio@...ck.org,
        linux-api@...r.kernel.org, hch@...radead.org
Subject: Re: [PATCH v5 3/5] fs: Add aio iopriority support

adam.manzanares@....com writes:

> From: Adam Manzanares <adam.manzanares@....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@....com>

Reviewed-by: Jeff Moyer <jmoyer@...hat.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 {