Add polled variants of the read and write commands. These act like their non-polled counterparts, except we expect to poll for completion of them.
To use polling, io_uring_setup() must be used with the IORING_SETUP_IOPOLL flag being set. It is illegal to mix and match polled and non-polled IO on an io_uring. Signed-off-by: Jens Axboe <[email protected]> --- fs/io_uring.c | 227 +++++++++++++++++++++++++++++++++- include/uapi/linux/io_uring.h | 10 +- 2 files changed, 227 insertions(+), 10 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index ae2b886282bb..02eab2f42c63 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -76,7 +76,14 @@ struct io_ring_ctx { struct work_struct work; + /* iopoll submission state */ struct { + spinlock_t poll_lock; + struct list_head poll_submitted; + } ____cacheline_aligned_in_smp; + + struct { + struct list_head poll_completing; struct mutex uring_lock; } ____cacheline_aligned_in_smp; @@ -106,10 +113,14 @@ struct io_kiocb { unsigned long ki_index; struct list_head ki_list; unsigned long ki_flags; +#define KIOCB_F_IOPOLL_COMPLETED 0 /* polled IO has completed */ +#define KIOCB_F_IOPOLL_EAGAIN 1 /* submission got EAGAIN */ }; #define IO_PLUG_THRESHOLD 2 +#define IO_IOPOLL_BATCH 8 + static struct kmem_cache *kiocb_cachep, *ioctx_cachep; static const struct file_operations io_scqring_fops; @@ -138,6 +149,9 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) spin_lock_init(&ctx->completion_lock); mutex_init(&ctx->ring_lock); init_waitqueue_head(&ctx->wait); + spin_lock_init(&ctx->poll_lock); + INIT_LIST_HEAD(&ctx->poll_submitted); + INIT_LIST_HEAD(&ctx->poll_completing); mutex_init(&ctx->uring_lock); return ctx; @@ -185,6 +199,15 @@ static inline void iocb_put(struct io_kiocb *iocb) kmem_cache_free(kiocb_cachep, iocb); } +static void iocb_put_many(struct io_ring_ctx *ctx, void **iocbs, int *nr) +{ + if (*nr) { + percpu_ref_put_many(&ctx->refs, *nr); + kmem_cache_free_bulk(kiocb_cachep, *nr, iocbs); + *nr = 0; + } +} + static void io_complete_iocb(struct io_ring_ctx *ctx, struct io_kiocb *iocb) { if (waitqueue_active(&ctx->wait)) @@ -192,6 +215,134 @@ static void io_complete_iocb(struct io_ring_ctx *ctx, struct io_kiocb *iocb) iocb_put(iocb); } +/* + * Find and free completed poll iocbs + */ +static void io_iopoll_reap(struct io_ring_ctx *ctx, unsigned int *nr_events) +{ + void *iocbs[IO_IOPOLL_BATCH]; + struct io_kiocb *iocb, *n; + int to_free = 0; + + list_for_each_entry_safe(iocb, n, &ctx->poll_completing, ki_list) { + if (!test_bit(KIOCB_F_IOPOLL_COMPLETED, &iocb->ki_flags)) + continue; + if (to_free == ARRAY_SIZE(iocbs)) + iocb_put_many(ctx, iocbs, &to_free); + + list_del(&iocb->ki_list); + iocbs[to_free++] = iocb; + + fput(iocb->rw.ki_filp); + (*nr_events)++; + } + + if (to_free) + iocb_put_many(ctx, iocbs, &to_free); +} + +/* + * 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 io_iopoll_getevents(struct io_ring_ctx *ctx, unsigned int *nr_events, + long min) +{ + struct io_kiocb *iocb; + int found, polled, ret; + + /* + * Check if we already have done events that satisfy what we need + */ + if (!list_empty(&ctx->poll_completing)) { + io_iopoll_reap(ctx, nr_events); + if (min && *nr_events >= min) + 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. + */ + io_iopoll_reap(ctx, nr_events); + if (min && *nr_events >= min) + return 0; + + polled = found = 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(KIOCB_F_IOPOLL_COMPLETED, &iocb->ki_flags)) + break; + + found++; + ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin); + if (ret < 0) + return ret; + + polled += ret; + } + + io_iopoll_reap(ctx, nr_events); + if (*nr_events >= min) + return 0; + return found; +} + +/* + * We can't just wait for polled events to come to us, we have to actively + * find and complete them. + */ +static void io_iopoll_reap_events(struct io_ring_ctx *ctx) +{ + if (!(ctx->flags & IORING_SETUP_IOPOLL)) + return; + + while (!list_empty_careful(&ctx->poll_submitted) || + !list_empty(&ctx->poll_completing)) { + unsigned int nr_events = 0; + + io_iopoll_getevents(ctx, &nr_events, 1); + } +} + +static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, + long min) +{ + int ret = 0; + + while (!*nr_events || !need_resched()) { + int tmin = 0; + + if (*nr_events < min) + tmin = min - *nr_events; + + ret = io_iopoll_getevents(ctx, nr_events, tmin); + if (ret <= 0) + break; + ret = 0; + } + + return ret; +} + static void kiocb_end_write(struct kiocb *kiocb) { if (kiocb->ki_flags & IOCB_WRITE) { @@ -253,8 +404,23 @@ static void io_complete_scqring_rw(struct kiocb *kiocb, long res, long res2) io_complete_scqring(iocb, res, 0); } +static void io_complete_scqring_iopoll(struct kiocb *kiocb, long res, long res2) +{ + struct io_kiocb *iocb = container_of(kiocb, struct io_kiocb, rw); + + kiocb_end_write(kiocb); + + if (unlikely(res == -EAGAIN)) { + set_bit(KIOCB_F_IOPOLL_EAGAIN, &iocb->ki_flags); + } else { + io_cqring_fill_event(iocb, res, 0); + set_bit(KIOCB_F_IOPOLL_COMPLETED, &iocb->ki_flags); + } +} + static int io_prep_rw(struct io_kiocb *kiocb, const struct io_uring_iocb *iocb) { + struct io_ring_ctx *ctx = kiocb->ki_ctx; struct kiocb *req = &kiocb->rw; int ret; @@ -277,9 +443,19 @@ static int io_prep_rw(struct io_kiocb *kiocb, const struct io_uring_iocb *iocb) if (unlikely(ret)) goto out_fput; - /* no one is going to poll for this I/O */ - req->ki_flags &= ~IOCB_HIPRI; - req->ki_complete = io_complete_scqring_rw; + if (ctx->flags & IORING_SETUP_IOPOLL) { + 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 = io_complete_scqring_iopoll; + } else { + /* no one is going to poll for this I/O */ + req->ki_flags &= ~IOCB_HIPRI; + req->ki_complete = io_complete_scqring_rw; + } return 0; out_fput: fput(req->ki_filp); @@ -317,6 +493,30 @@ static inline void io_rw_done(struct kiocb *req, ssize_t ret) } } +/* + * 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 io_iopoll_iocb_issued(struct io_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 = test_bit(KIOCB_F_IOPOLL_COMPLETED, &kiocb->ki_flags); + struct io_ring_ctx *ctx = kiocb->ki_ctx; + + spin_lock(&ctx->poll_lock); + if (front) + 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 io_read(struct io_kiocb *kiocb, const struct io_uring_iocb *iocb) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; @@ -459,9 +659,13 @@ static int __io_submit_one(struct io_ring_ctx *ctx, ret = io_write(req, iocb); break; case IORING_OP_FSYNC: + if (ctx->flags & IORING_SETUP_IOPOLL) + break; ret = io_fsync(&req->fsync, iocb, false); break; case IORING_OP_FDSYNC: + if (ctx->flags & IORING_SETUP_IOPOLL) + break; ret = io_fsync(&req->fsync, iocb, true); break; default: @@ -475,6 +679,13 @@ static int __io_submit_one(struct io_ring_ctx *ctx, */ if (ret) goto out_put_req; + if (ctx->flags & IORING_SETUP_IOPOLL) { + if (test_bit(KIOCB_F_IOPOLL_EAGAIN, &req->ki_flags)) { + ret = -EAGAIN; + goto out_put_req; + } + io_iopoll_iocb_issued(req); + } return 0; out_put_req: iocb_put(req); @@ -589,12 +800,17 @@ static int __io_uring_enter(struct io_ring_ctx *ctx, unsigned to_submit, return ret; } if (flags & IORING_ENTER_GETEVENTS) { + unsigned nr_events = 0; int get_ret; if (!ret && to_submit) min_complete = 0; - get_ret = io_cqring_wait(ctx, min_complete); + if (ctx->flags & IORING_SETUP_IOPOLL) + get_ret = io_iopoll_check(ctx, &nr_events, + min_complete); + else + get_ret = io_cqring_wait(ctx, min_complete); if (get_ret < 0 && !ret) ret = get_ret; } @@ -622,6 +838,7 @@ static void io_ring_ctx_free(struct work_struct *work) { struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, work); + io_iopoll_reap_events(ctx); io_free_scq_urings(ctx); percpu_ref_exit(&ctx->refs); kmem_cache_free(ioctx_cachep, ctx); @@ -825,7 +1042,7 @@ SYSCALL_DEFINE3(io_uring_setup, u32, entries, struct iovec __user *, iovecs, return -EINVAL; } - if (p.flags) + if (p.flags & ~IORING_SETUP_IOPOLL) return -EINVAL; if (iovecs) return -EINVAL; diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index c31ac84d9f53..f7ba30747816 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -31,6 +31,11 @@ struct io_uring_iocb { }; }; +/* + * io_uring_setup() flags + */ +#define IORING_SETUP_IOPOLL (1 << 0) /* io_context is polled */ + #define IORING_OP_READ 1 #define IORING_OP_WRITE 2 #define IORING_OP_FSYNC 3 @@ -45,11 +50,6 @@ struct io_uring_event { __u32 flags; }; -/* - * io_uring_event->flags - */ -#define IOEV_FLAG_CACHEHIT (1 << 0) /* IO did not hit media */ - /* * Magic offsets for the application to mmap the data it needs */ -- 2.17.1
