Hi, Adam, adam.manzanares@xxxxxxx writes: > From: Adam Manzanares <adam.manzanares@xxxxxxx> > > 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. > > See the following link for performance implications on a SATA HDD: > https://lkml.org/lkml/2016/12/6/495 > > Given that WRR support for NVME devices has patches floating around and it was > discussed at LSFMM, we may soon have a lower latency storage device that can > make use of iopriorities. A per command iopriority interface seems timely > given these developments. > > If we want to avoid bloating struct kiocb, I suggest we turn the private field > into a union of the private and ki_ioprio field. It seems like the users of > the private field all use it at a point where we can yank the priority from > the kiocb before the private field is used. Comments and suggestions welcome. The ioprio_set system call requires CAP_SYS_ADMIN for setting IOPRIO_CLASS_RT. I think we need similar checks here. -Jeff > > v2: merge patches > use IOCB_FLAG_IOPRIO > validate intended use with IOCB_IOPRIO > add linux-api and linux-block to cc > > Signed-off-by: Adam Manzanares <adam.manzanares@xxxxxxx> > --- > fs/aio.c | 10 ++++++++++ > fs/block_dev.c | 2 ++ > include/linux/fs.h | 2 ++ > include/uapi/linux/aio_abi.h | 1 + > 4 files changed, 15 insertions(+) > > diff --git a/fs/aio.c b/fs/aio.c > index 88d7927ffbc6..f36636d8ff2c 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -1597,6 +1597,16 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, > req->common.ki_flags |= IOCB_EVENTFD; > } > > + 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. > + */ > + req->common.ki_ioprio = iocb->aio_reqprio; > + req->common.ki_flags |= IOCB_IOPRIO; > + } > + > ret = kiocb_set_rw_flags(&req->common, iocb->aio_rw_flags); > if (unlikely(ret)) { > pr_debug("EINVAL: aio_rw_flags\n"); > 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 760d8da1b6c7..ab63ce720305 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -292,6 +292,7 @@ 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; > @@ -300,6 +301,7 @@ struct kiocb { > void *private; > int ki_flags; > enum rw_hint 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 a04adbc70ddf..d4593a6062ef 100644 > --- a/include/uapi/linux/aio_abi.h > +++ b/include/uapi/linux/aio_abi.h > @@ -54,6 +54,7 @@ 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 {
