On Jun 13, 2017, at 10:01 PM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>
> Add four flags for the pwritev2(2) system call, allowing an application
> to give the kernel a hint about what on-media life times can be
> expected from a given write.
>
> The intent is for these values to be relative to each other, no
> absolute meaning should be attached to these flag names.
>
> Define IOCB flags to carry this information over, and finally
> transform them into the block defined stream values.
>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
> ---
> fs/read_write.c | 9 ++++++++-
> include/linux/fs.h | 12 ++++++++++++
> include/uapi/linux/fs.h | 10 ++++++++++
> 3 files changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 47c1d4484df9..a9b0c3125e0f 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -678,7 +678,7 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
> struct kiocb kiocb;
> ssize_t ret;
>
> - if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))
> + if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_WRITE_LIFE_MASK))
> return -EOPNOTSUPP;
>
> init_sync_kiocb(&kiocb, filp);
> @@ -688,6 +688,13 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
> kiocb.ki_flags |= IOCB_DSYNC;
> if (flags & RWF_SYNC)
> kiocb.ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
> + if (flags & RWF_WRITE_LIFE_MASK) {
> + struct inode *inode = file_inode(filp);
> +
> + inode->i_stream = (flags & RWF_WRITE_LIFE_MASK) >>
> + RWF_WRITE_LIFE_SHIFT;
> + kiocb.ki_flags |= inode->i_stream << IOCB_WRITE_LIFE_SHIFT;
> + }
> kiocb.ki_pos = *ppos;
>
> if (type == READ)
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 771e172d23d7..751a1046e87b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -269,6 +269,12 @@ struct writeback_control;
> #define IOCB_SYNC (1 << 5)
> #define IOCB_WRITE (1 << 6)
>
> +/*
> + * Steal 4-bits for stream information, this allows 16 valid streams
> + */
> +#define IOCB_WRITE_LIFE_SHIFT 7
> +#define IOCB_WRITE_LIFE_MASK (BIT(7) | BIT(8) | BIT(9) | BIT(10))
> +
> struct kiocb {
> struct file *ki_filp;
> loff_t ki_pos;
> @@ -292,6 +298,12 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
> };
> }
>
> +static inline int iocb_streamid(const struct kiocb *iocb)
> +{
> + return (iocb->ki_flags & IOCB_WRITE_LIFE_MASK) >>
> + IOCB_WRITE_LIFE_SHIFT;
> +}
> +
> /*
> * "descriptor" for what we're up to with a read.
> * This allows us to use the same read code yet
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 24e61a54feaa..8a7e6f26f6f5 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -361,4 +361,14 @@ struct fscrypt_key {
> #define RWF_DSYNC 0x00000002 /* per-IO O_DSYNC */
> #define RWF_SYNC 0x00000004 /* per-IO O_SYNC */
>
> +/*
> + * Data life time write flags, steal 4 bits for that
> + */
> +#define RWF_WRITE_LIFE_SHIFT 3
> +#define RWF_WRITE_LIFE_MASK 0x000000f0 /* 4 bits of stream ID */
> +#define RWF_WRITE_LIFE_SHORT (1 << RWF_WRITE_LIFE_SHIFT)
> +#define RWF_WRITE_LIFE_MEDIUM (2 << RWF_WRITE_LIFE_SHIFT)
> +#define RWF_WRITE_LIFE_LONG (3 << RWF_WRITE_LIFE_SHIFT)
> +#define RWF_WRITE_LIFE_EXTREME (4 << RWF_WRITE_LIFE_SHIFT)
> +
> #endif /* _UAPI_LINUX_FS_H */
> --
> 2.7.4
>
Cheers, Andreas
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