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. Reviewed-by: Benny Halevy <bhalevy@xxxxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- fs/aio.c | 415 +++++++++++++++++++++++++++++++---- include/uapi/linux/aio_abi.h | 4 + 2 files changed, 380 insertions(+), 39 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 958f432a0e5b..f7992c7123bc 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -76,6 +76,8 @@ struct aio_ring { */ #define AIO_PLUG_THRESHOLD 2 +#define AIO_IOPOLL_BATCH 8 + #define AIO_RING_PAGES 8 struct kioctx_table { @@ -147,6 +149,18 @@ 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 */ @@ -199,14 +213,27 @@ 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 KIOCB_F_POLL_COMPLETED 0 /* polled IO has completed */ +#define KIOCB_F_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----*/ @@ -223,6 +250,8 @@ static struct vfsmount *aio_mnt; static const struct file_operations aio_ring_fops; static const struct address_space_operations aio_ctx_aops; +static void aio_iopoll_reap_events(struct kioctx *); + static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages) { struct file *file; @@ -460,11 +489,15 @@ 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) @@ -548,6 +581,14 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events) return 0; } +/* + * Don't support cancel on anything that isn't old aio + */ +static bool aio_ctx_supports_cancel(struct kioctx *ctx) +{ + return (ctx->flags & IOCTX_FLAG_IOPOLL) == 0; +} + #define AIO_EVENTS_PER_PAGE (PAGE_SIZE / sizeof(struct io_event)) #define AIO_EVENTS_FIRST_PAGE ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event)) #define AIO_EVENTS_OFFSET (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE) @@ -558,6 +599,8 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel) struct kioctx *ctx = req->ki_ctx; unsigned long flags; + if (WARN_ON_ONCE(!aio_ctx_supports_cancel(ctx))) + return; if (WARN_ON_ONCE(!list_empty(&req->ki_list))) return; @@ -746,6 +789,11 @@ 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; @@ -817,11 +865,15 @@ 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])); @@ -1030,6 +1082,7 @@ 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; @@ -1072,6 +1125,15 @@ 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) { @@ -1261,6 +1323,183 @@ static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr, return ret < 0 || *i >= min_nr; } +/* + * 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(KIOCB_F_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(KIOCB_F_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()) { + 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) @@ -1305,7 +1544,9 @@ SYSCALL_DEFINE5(io_setup2, u32, nr_events, u32, flags, void __user *, user1, unsigned long ctx; long ret; - if (flags || user1 || user2) + if (user1 || user2) + return -EINVAL; + if (flags & ~IOCTX_FLAG_IOPOLL) return -EINVAL; ret = get_user(ctx, ctxp); @@ -1431,13 +1672,8 @@ 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); @@ -1449,19 +1685,44 @@ 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); + + if (unlikely(res == -EAGAIN)) { + set_bit(KIOCB_F_POLL_EAGAIN, &iocb->ki_flags); + } else { + aio_fill_event(&iocb->ki_ev, iocb, res, res2); + set_bit(KIOCB_F_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) @@ -1487,9 +1748,35 @@ 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; @@ -1534,15 +1821,40 @@ 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 = test_bit(KIOCB_F_POLL_COMPLETED, &kiocb->ki_flags); + struct kioctx *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 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; @@ -1567,15 +1879,16 @@ 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; @@ -1846,7 +2159,8 @@ 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; @@ -1869,35 +2183,44 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb, } } - ret = put_user(KIOCB_KEY, &user_iocb->aio_key); - if (unlikely(ret)) { - pr_debug("EFAULT: aio_key\n"); - goto out_put_req; + if (aio_ctx_supports_cancel(ctx)) { + ret = put_user(KIOCB_KEY, &user_iocb->aio_key); + if (unlikely(ret)) { + pr_debug("EFAULT: aio_key\n"); + goto out_put_req; + } } 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: @@ -1913,13 +2236,21 @@ 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(KIOCB_F_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; } @@ -2075,6 +2406,9 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, if (unlikely(!ctx)) return -EINVAL; + if (!aio_ctx_supports_cancel(ctx)) + goto err; + spin_lock_irq(&ctx->ctx_lock); kiocb = lookup_kiocb(ctx, iocb); if (kiocb) { @@ -2091,9 +2425,8 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, */ ret = -EINPROGRESS; } - +err: percpu_ref_put(&ctx->users); - return ret; } @@ -2108,8 +2441,12 @@ 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 8387e0af0f76..a6829bae9ada 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 { @@ -106,6 +108,8 @@ struct iocb { __u32 aio_resfd; }; /* 64 bytes */ +#define IOCTX_FLAG_IOPOLL (1 << 0) /* io_context is polled */ + #undef IFBIG #undef IFLITTLE -- 2.17.1