On Fri, 2018-12-07 at 15:20 -0700, Jens Axboe wrote:
> Add polled variants of PREAD/PREADV and PWRITE/PWRITEV. These act
> like their non-polled counterparts, except we expect to poll for
> completion of them. The polling happens at io_getevent() time, and
> works just like non-polled IO.
>
> To setup an io_context for polled IO, the application must call
> io_setup2() with IOCTX_FLAG_IOPOLL as one of the flags. It is illegal
> to mix and match polled and non-polled IO on an io_context.
>
> Polled IO doesn't support the user mapped completion ring. Events
> must be reaped through the io_getevents() system call. For non-irq
> driven poll devices, there's no way to support completion reaping
> from userspace by just looking at the ring. The application itself
> is the one that pulls completion entries.
>
> Signed-off-by: Jens Axboe <ax...@kernel.dk>
> ---
> fs/aio.c | 396 +++++++++++++++++++++++++++++++----
> include/uapi/linux/aio_abi.h | 3 +
> 2 files changed, 363 insertions(+), 36 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index bb6f07ca6940..cc8763b395c1 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -153,6 +153,18 @@ struct kioctx {
> atomic_t reqs_available;
> } ____cacheline_aligned_in_smp;
>
> + /* iopoll submission state */
> + struct {
> + spinlock_t poll_lock;
> + struct list_head poll_submitted;
> + } ____cacheline_aligned_in_smp;
> +
> + /* iopoll completion state */
> + struct {
> + struct list_head poll_completing;
> + struct mutex getevents_lock;
> + } ____cacheline_aligned_in_smp;
> +
> struct {
> spinlock_t ctx_lock;
> struct list_head active_reqs; /* used for cancellation */
> @@ -205,14 +217,27 @@ struct aio_kiocb {
> __u64 ki_user_data; /* user's data for completion */
>
> struct list_head ki_list; /* the aio core uses this
> - * for cancellation */
> + * for cancellation, or for
> + * polled IO */
> +
> + unsigned long ki_flags;
> +#define IOCB_POLL_COMPLETED 0 /* polled IO has completed */
> +#define IOCB_POLL_EAGAIN 1 /* polled submission got EAGAIN */
> +
> refcount_t ki_refcnt;
>
> - /*
> - * If the aio_resfd field of the userspace iocb is not zero,
> - * this is the underlying eventfd context to deliver events to.
> - */
> - struct eventfd_ctx *ki_eventfd;
> + union {
> + /*
> + * If the aio_resfd field of the userspace iocb is not zero,
> + * this is the underlying eventfd context to deliver events to.
> + */
> + struct eventfd_ctx *ki_eventfd;
> +
> + /*
> + * For polled IO, stash completion info here
> + */
> + struct io_event ki_ev;
> + };
> };
>
> /*------ sysctl variables----*/
> @@ -233,6 +258,7 @@ static const unsigned int iocb_page_shift =
> ilog2(PAGE_SIZE / sizeof(struct iocb));
>
> static void aio_useriocb_unmap(struct kioctx *);
> +static void aio_iopoll_reap_events(struct kioctx *);
>
> static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
> {
> @@ -471,11 +497,15 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned
> int nr_events)
> int i;
> struct file *file;
>
> - /* Compensate for the ring buffer's head/tail overlap entry */
> - nr_events += 2; /* 1 is required, 2 for good luck */
> -
> + /*
> + * Compensate for the ring buffer's head/tail overlap entry.
> + * IO polling doesn't require any io event entries
> + */
> size = sizeof(struct aio_ring);
> - size += sizeof(struct io_event) * nr_events;
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL)) {
> + nr_events += 2; /* 1 is required, 2 for good luck */
> + size += sizeof(struct io_event) * nr_events;
> + }
>
> nr_pages = PFN_UP(size);
> if (nr_pages < 0)
> @@ -758,6 +788,11 @@ static struct kioctx *io_setup_flags(unsigned long ctxid,
>
> INIT_LIST_HEAD(&ctx->active_reqs);
>
> + spin_lock_init(&ctx->poll_lock);
> + INIT_LIST_HEAD(&ctx->poll_submitted);
> + INIT_LIST_HEAD(&ctx->poll_completing);
> + mutex_init(&ctx->getevents_lock);
> +
> if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
> goto err;
>
> @@ -829,11 +864,15 @@ static int kill_ioctx(struct mm_struct *mm, struct
> kioctx *ctx,
> {
> struct kioctx_table *table;
>
> + mutex_lock(&ctx->getevents_lock);
> spin_lock(&mm->ioctx_lock);
> if (atomic_xchg(&ctx->dead, 1)) {
> spin_unlock(&mm->ioctx_lock);
> + mutex_unlock(&ctx->getevents_lock);
> return -EINVAL;
> }
> + aio_iopoll_reap_events(ctx);
> + mutex_unlock(&ctx->getevents_lock);
>
> table = rcu_dereference_raw(mm->ioctx_table);
> WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
> @@ -1042,6 +1081,7 @@ static inline struct aio_kiocb *aio_get_req(struct
> kioctx *ctx)
> percpu_ref_get(&ctx->reqs);
> req->ki_ctx = ctx;
> INIT_LIST_HEAD(&req->ki_list);
> + req->ki_flags = 0;
> refcount_set(&req->ki_refcnt, 0);
> req->ki_eventfd = NULL;
> return req;
> @@ -1083,6 +1123,15 @@ static inline void iocb_put(struct aio_kiocb *iocb)
> }
> }
>
> +static void iocb_put_many(struct kioctx *ctx, void **iocbs, int *nr)
> +{
> + if (*nr) {
> + percpu_ref_put_many(&ctx->reqs, *nr);
> + kmem_cache_free_bulk(kiocb_cachep, *nr, iocbs);
> + *nr = 0;
> + }
> +}
> +
> static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb,
> long res, long res2)
> {
> @@ -1272,6 +1321,185 @@ static bool aio_read_events(struct kioctx *ctx, long
> min_nr, long nr,
> return ret < 0 || *i >= min_nr;
> }
>
> +#define AIO_IOPOLL_BATCH 8
> +
> +/*
> + * Process completed iocb iopoll entries, copying the result to userspace.
> + */
> +static long aio_iopoll_reap(struct kioctx *ctx, struct io_event __user *evs,
> + unsigned int *nr_events, long max)
> +{
> + void *iocbs[AIO_IOPOLL_BATCH];
> + struct aio_kiocb *iocb, *n;
> + int to_free = 0, ret = 0;
> +
> + /* Shouldn't happen... */
> + if (*nr_events >= max)
> + return 0;
> +
> + list_for_each_entry_safe(iocb, n, &ctx->poll_completing, ki_list) {
> + if (*nr_events == max)
> + break;
> + if (!test_bit(IOCB_POLL_COMPLETED, &iocb->ki_flags))
> + continue;
> + if (to_free == AIO_IOPOLL_BATCH)
> + iocb_put_many(ctx, iocbs, &to_free);
> +
> + list_del(&iocb->ki_list);
> + iocbs[to_free++] = iocb;
> +
> + fput(iocb->rw.ki_filp);
> +
> + if (evs && copy_to_user(evs + *nr_events, &iocb->ki_ev,
> + sizeof(iocb->ki_ev))) {
> + ret = -EFAULT;
> + break;
> + }
> + (*nr_events)++;
> + }
> +
> + if (to_free)
> + iocb_put_many(ctx, iocbs, &to_free);
> +
> + return ret;
> +}
> +
> +/*
> + * Poll for a mininum of 'min' events, and a maximum of 'max'. Note that if
> + * min == 0 we consider that a non-spinning poll check - we'll still enter
> + * the driver poll loop, but only as a non-spinning completion check.
> + */
> +static int aio_iopoll_getevents(struct kioctx *ctx,
> + struct io_event __user *event,
> + unsigned int *nr_events, long min, long max)
> +{
> + struct aio_kiocb *iocb;
> + int to_poll, polled, ret;
> +
> + /*
> + * Check if we already have done events that satisfy what we need
> + */
> + if (!list_empty(&ctx->poll_completing)) {
> + ret = aio_iopoll_reap(ctx, event, nr_events, max);
> + if (ret < 0)
> + return ret;
> + if ((min && *nr_events >= min) || *nr_events >= max)
> + return 0;
> + }
> +
> + /*
> + * Take in a new working set from the submitted list, if possible.
> + */
> + if (!list_empty_careful(&ctx->poll_submitted)) {
> + spin_lock(&ctx->poll_lock);
> + list_splice_init(&ctx->poll_submitted, &ctx->poll_completing);
> + spin_unlock(&ctx->poll_lock);
> + }
> +
> + if (list_empty(&ctx->poll_completing))
> + return 0;
> +
> + /*
> + * Check again now that we have a new batch.
> + */
> + ret = aio_iopoll_reap(ctx, event, nr_events, max);
> + if (ret < 0)
> + return ret;
> + if ((min && *nr_events >= min) || *nr_events >= max)
> + return 0;
> +
> + /*
> + * Find up to 'max' worth of events to poll for, including the
> + * events we already successfully polled
> + */
> + polled = to_poll = 0;
> + list_for_each_entry(iocb, &ctx->poll_completing, ki_list) {
> + /*
> + * Poll for needed events with spin == true, anything after
> + * that we just check if we have more, up to max.
> + */
> + bool spin = !polled || *nr_events < min;
> + struct kiocb *kiocb = &iocb->rw;
> +
> + if (test_bit(IOCB_POLL_COMPLETED, &iocb->ki_flags))
> + break;
> + if (++to_poll + *nr_events > max)
> + break;
> +
> + ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
> + if (ret < 0)
> + return ret;
> +
> + polled += ret;
> + if (polled + *nr_events >= max)
> + break;
> + }
> +
> + ret = aio_iopoll_reap(ctx, event, nr_events, max);
> + if (ret < 0)
> + return ret;
> + if (*nr_events >= min)
> + return 0;
> + return to_poll;
> +}
> +
> +/*
> + * We can't just wait for polled events to come to us, we have to actively
> + * find and complete them.
> + */
> +static void aio_iopoll_reap_events(struct kioctx *ctx)
> +{
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL))
> + return;
> +
> + while (!list_empty_careful(&ctx->poll_submitted) ||
> + !list_empty(&ctx->poll_completing)) {
> + unsigned int nr_events = 0;
> +
> + aio_iopoll_getevents(ctx, NULL, &nr_events, 1, UINT_MAX);
> + }
> +}
> +
> +static int __aio_iopoll_check(struct kioctx *ctx, struct io_event __user
> *event,
> + unsigned int *nr_events, long min_nr, long max_nr)
> +{
> + int ret = 0;
> +
> + while (!*nr_events || !need_resched()) {
Hmm, it doesn't make sense to spin in this loop
if the user got _all_ the events he requested, even
if !need_resched(). How about:
while (!*nr_events || (!need_resched() && *nr_events < max_nr)) {
> + int tmin = 0;
> +
> + if (*nr_events < min_nr)
> + tmin = min_nr - *nr_events;
> +
> + ret = aio_iopoll_getevents(ctx, event, nr_events, tmin, max_nr);
> + if (ret <= 0)
> + break;
> + ret = 0;
> + }
> +
> + return ret;
> +}
> +
> +static int aio_iopoll_check(struct kioctx *ctx, long min_nr, long nr,
> + struct io_event __user *event)
> +{
> + unsigned int nr_events = 0;
> + int ret;
> +
> + /* Only allow one thread polling at a time */
> + if (!mutex_trylock(&ctx->getevents_lock))
> + return -EBUSY;
> + if (unlikely(atomic_read(&ctx->dead))) {
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + ret = __aio_iopoll_check(ctx, event, &nr_events, min_nr, nr);
> +err:
> + mutex_unlock(&ctx->getevents_lock);
> + return nr_events ? nr_events : ret;
> +}
> +
> static long read_events(struct kioctx *ctx, long min_nr, long nr,
> struct io_event __user *event,
> ktime_t until)
> @@ -1375,7 +1603,7 @@ SYSCALL_DEFINE6(io_setup2, u32, nr_events, u32, flags,
> struct iocb __user *,
>
> if (user1 || user2)
> return -EINVAL;
> - if (flags & ~IOCTX_FLAG_USERIOCB)
> + if (flags & ~(IOCTX_FLAG_USERIOCB | IOCTX_FLAG_IOPOLL))
> return -EINVAL;
>
> ret = get_user(ctx, ctxp);
> @@ -1509,13 +1737,8 @@ static void aio_remove_iocb(struct aio_kiocb *iocb)
> spin_unlock_irqrestore(&ctx->ctx_lock, flags);
> }
>
> -static void aio_complete_rw(struct kiocb *kiocb, long res, long res2)
> +static void kiocb_end_write(struct kiocb *kiocb)
> {
> - struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, rw);
> -
> - if (!list_empty_careful(&iocb->ki_list))
> - aio_remove_iocb(iocb);
> -
> if (kiocb->ki_flags & IOCB_WRITE) {
> struct inode *inode = file_inode(kiocb->ki_filp);
>
> @@ -1527,19 +1750,48 @@ static void aio_complete_rw(struct kiocb *kiocb, long
> res, long res2)
> __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
> file_end_write(kiocb->ki_filp);
> }
> +}
> +
> +static void aio_complete_rw(struct kiocb *kiocb, long res, long res2)
> +{
> + struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, rw);
> +
> + if (!list_empty_careful(&iocb->ki_list))
> + aio_remove_iocb(iocb);
> +
> + kiocb_end_write(kiocb);
>
> fput(kiocb->ki_filp);
> aio_complete(iocb, res, res2);
> }
>
> -static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb)
> +static void aio_complete_rw_poll(struct kiocb *kiocb, long res, long res2)
> {
> + struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, rw);
> +
> + kiocb_end_write(kiocb);
> +
> + /*
> + * Handle EAGAIN from resource limits with polled IO inline, don't
> + * pass the event back to userspace.
> + */
> + if (unlikely(res == -EAGAIN))
> + set_bit(IOCB_POLL_EAGAIN, &iocb->ki_flags);
> + else {
> + aio_fill_event(&iocb->ki_ev, iocb, res, res2);
> + set_bit(IOCB_POLL_COMPLETED, &iocb->ki_flags);
> + }
> +}
> +
> +static int aio_prep_rw(struct aio_kiocb *kiocb, const struct iocb *iocb)
> +{
> + struct kioctx *ctx = kiocb->ki_ctx;
> + struct kiocb *req = &kiocb->rw;
> int ret;
>
> req->ki_filp = fget(iocb->aio_fildes);
> if (unlikely(!req->ki_filp))
> return -EBADF;
> - req->ki_complete = aio_complete_rw;
> req->ki_pos = iocb->aio_offset;
> req->ki_flags = iocb_flags(req->ki_filp);
> if (iocb->aio_flags & IOCB_FLAG_RESFD)
> @@ -1565,9 +1817,35 @@ static int aio_prep_rw(struct kiocb *req, const struct
> iocb *iocb)
> if (unlikely(ret))
> goto out_fput;
>
> - req->ki_flags &= ~IOCB_HIPRI; /* no one is going to poll for this I/O */
> - return 0;
> + if (iocb->aio_flags & IOCB_FLAG_HIPRI) {
> + /* shares space in the union, and is rather pointless.. */
> + ret = -EINVAL;
> + if (iocb->aio_flags & IOCB_FLAG_RESFD)
> + goto out_fput;
> +
> + /* can't submit polled IO to a non-polled ctx */
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL))
> + goto out_fput;
> +
> + ret = -EOPNOTSUPP;
> + if (!(req->ki_flags & IOCB_DIRECT) ||
> + !req->ki_filp->f_op->iopoll)
> + goto out_fput;
> +
> + req->ki_flags |= IOCB_HIPRI;
> + req->ki_complete = aio_complete_rw_poll;
> + } else {
> + /* can't submit non-polled IO to a polled ctx */
> + ret = -EINVAL;
> + if (ctx->flags & IOCTX_FLAG_IOPOLL)
> + goto out_fput;
>
> + /* no one is going to poll for this I/O */
> + req->ki_flags &= ~IOCB_HIPRI;
> + req->ki_complete = aio_complete_rw;
> + }
> +
> + return 0;
> out_fput:
> fput(req->ki_filp);
> return ret;
> @@ -1612,15 +1890,40 @@ static inline void aio_rw_done(struct kiocb *req,
> ssize_t ret)
> }
> }
>
> -static ssize_t aio_read(struct kiocb *req, const struct iocb *iocb,
> +/*
> + * After the iocb has been issued, it's safe to be found on the poll list.
> + * Adding the kiocb to the list AFTER submission ensures that we don't
> + * find it from a io_getevents() thread before the issuer is done accessing
> + * the kiocb cookie.
> + */
> +static void aio_iopoll_iocb_issued(struct aio_kiocb *kiocb)
> +{
> + /*
> + * For fast devices, IO may have already completed. If it has, add
> + * it to the front so we find it first. We can't add to the poll_done
> + * list as that's unlocked from the completion side.
> + */
> + const int front_add = test_bit(IOCB_POLL_COMPLETED, &kiocb->ki_flags);
> + struct kioctx *ctx = kiocb->ki_ctx;
> +
> + spin_lock(&ctx->poll_lock);
> + if (front_add)
> + list_add(&kiocb->ki_list, &ctx->poll_submitted);
> + else
> + list_add_tail(&kiocb->ki_list, &ctx->poll_submitted);
> + spin_unlock(&ctx->poll_lock);
> +}
> +
> +static ssize_t aio_read(struct aio_kiocb *kiocb, const struct iocb *iocb,
> bool vectored, bool compat)
> {
> struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
> + struct kiocb *req = &kiocb->rw;
> struct iov_iter iter;
> struct file *file;
> ssize_t ret;
>
> - ret = aio_prep_rw(req, iocb);
> + ret = aio_prep_rw(kiocb, iocb);
> if (ret)
> return ret;
> file = req->ki_filp;
> @@ -1645,15 +1948,16 @@ static ssize_t aio_read(struct kiocb *req, const
> struct iocb *iocb,
> return ret;
> }
>
> -static ssize_t aio_write(struct kiocb *req, const struct iocb *iocb,
> +static ssize_t aio_write(struct aio_kiocb *kiocb, const struct iocb *iocb,
> bool vectored, bool compat)
> {
> struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
> + struct kiocb *req = &kiocb->rw;
> struct iov_iter iter;
> struct file *file;
> ssize_t ret;
>
> - ret = aio_prep_rw(req, iocb);
> + ret = aio_prep_rw(kiocb, iocb);
> if (ret)
> return ret;
> file = req->ki_filp;
> @@ -1924,7 +2228,8 @@ static int __io_submit_one(struct kioctx *ctx, const
> struct iocb *iocb,
> return -EINVAL;
> }
>
> - if (!get_reqs_available(ctx))
> + /* Poll IO doesn't need ring reservations */
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL) && !get_reqs_available(ctx))
> return -EAGAIN;
>
> ret = -EAGAIN;
> @@ -1947,8 +2252,8 @@ static int __io_submit_one(struct kioctx *ctx, const
> struct iocb *iocb,
> }
> }
>
> - /* Don't support cancel on user mapped iocbs */
> - if (!(ctx->flags & IOCTX_FLAG_USERIOCB)) {
> + /* Don't support cancel on user mapped iocbs or polled context */
> + if (!(ctx->flags & (IOCTX_FLAG_USERIOCB | IOCTX_FLAG_IOPOLL))) {
> ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
> if (unlikely(ret)) {
> pr_debug("EFAULT: aio_key\n");
> @@ -1959,26 +2264,33 @@ static int __io_submit_one(struct kioctx *ctx, const
> struct iocb *iocb,
> req->ki_user_iocb = user_iocb;
> req->ki_user_data = iocb->aio_data;
>
> + ret = -EINVAL;
> switch (iocb->aio_lio_opcode) {
> case IOCB_CMD_PREAD:
> - ret = aio_read(&req->rw, iocb, false, compat);
> + ret = aio_read(req, iocb, false, compat);
> break;
> case IOCB_CMD_PWRITE:
> - ret = aio_write(&req->rw, iocb, false, compat);
> + ret = aio_write(req, iocb, false, compat);
> break;
> case IOCB_CMD_PREADV:
> - ret = aio_read(&req->rw, iocb, true, compat);
> + ret = aio_read(req, iocb, true, compat);
> break;
> case IOCB_CMD_PWRITEV:
> - ret = aio_write(&req->rw, iocb, true, compat);
> + ret = aio_write(req, iocb, true, compat);
> break;
> case IOCB_CMD_FSYNC:
> + if (ctx->flags & IOCTX_FLAG_IOPOLL)
> + break;
> ret = aio_fsync(&req->fsync, iocb, false);
> break;
> case IOCB_CMD_FDSYNC:
> + if (ctx->flags & IOCTX_FLAG_IOPOLL)
> + break;
> ret = aio_fsync(&req->fsync, iocb, true);
> break;
> case IOCB_CMD_POLL:
> + if (ctx->flags & IOCTX_FLAG_IOPOLL)
> + break;
> ret = aio_poll(req, iocb);
> break;
> default:
> @@ -1994,13 +2306,21 @@ static int __io_submit_one(struct kioctx *ctx, const
> struct iocb *iocb,
> */
> if (ret)
> goto out_put_req;
> + if (ctx->flags & IOCTX_FLAG_IOPOLL) {
> + if (test_bit(IOCB_POLL_EAGAIN, &req->ki_flags)) {
> + ret = -EAGAIN;
> + goto out_put_req;
> + }
> + aio_iopoll_iocb_issued(req);
> + }
> return 0;
> out_put_req:
> if (req->ki_eventfd)
> eventfd_ctx_put(req->ki_eventfd);
> iocb_put(req);
> out_put_reqs_available:
> - put_reqs_available(ctx, 1);
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL))
> + put_reqs_available(ctx, 1);
> return ret;
> }
>
> @@ -2166,7 +2486,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id,
> struct iocb __user *, iocb,
> if (unlikely(!ctx))
> return -EINVAL;
>
> - if (ctx->flags & IOCTX_FLAG_USERIOCB)
> + if (ctx->flags & (IOCTX_FLAG_USERIOCB | IOCTX_FLAG_IOPOLL))
> goto err;
>
> spin_lock_irq(&ctx->ctx_lock);
> @@ -2201,8 +2521,12 @@ static long do_io_getevents(aio_context_t ctx_id,
> long ret = -EINVAL;
>
> if (likely(ioctx)) {
> - if (likely(min_nr <= nr && min_nr >= 0))
> - ret = read_events(ioctx, min_nr, nr, events, until);
> + if (likely(min_nr <= nr && min_nr >= 0)) {
> + if (ioctx->flags & IOCTX_FLAG_IOPOLL)
> + ret = aio_iopoll_check(ioctx, min_nr, nr,
> events);
> + else
> + ret = read_events(ioctx, min_nr, nr, events,
> until);
> + }
> percpu_ref_put(&ioctx->users);
> }
>
> diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
> index 814e6606c413..ea0b9a19f4df 100644
> --- a/include/uapi/linux/aio_abi.h
> +++ b/include/uapi/linux/aio_abi.h
> @@ -52,9 +52,11 @@ enum {
> * is valid.
> * IOCB_FLAG_IOPRIO - Set if the "aio_reqprio" member of the "struct iocb"
> * is valid.
> + * IOCB_FLAG_HIPRI - Use IO completion polling
> */
> #define IOCB_FLAG_RESFD (1 << 0)
> #define IOCB_FLAG_IOPRIO (1 << 1)
> +#define IOCB_FLAG_HIPRI (1 << 2)
>
> /* read() from /dev/aio returns these structures. */
> struct io_event {
> @@ -107,6 +109,7 @@ struct iocb {
> }; /* 64 bytes */
>
> #define IOCTX_FLAG_USERIOCB (1 << 0) /* iocbs are user mapped */
> +#define IOCTX_FLAG_IOPOLL (1 << 1) /* io_context is polled */
>
> #undef IFBIG
> #undef IFLITTLE
