diff options
| -rw-r--r-- | MAINTAINERS | 8 | ||||
| -rw-r--r-- | block/Makefile.objs | 3 | ||||
| -rw-r--r-- | block/io_uring.c | 401 | ||||
| -rw-r--r-- | include/block/aio.h | 16 | ||||
| -rw-r--r-- | include/block/raw-aio.h | 12 |
5 files changed, 439 insertions, 1 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index c45e886d88..a19437c13d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2634,6 +2634,14 @@ F: block/file-posix.c F: block/file-win32.c F: block/win32-aio.c +Linux io_uring +M: Aarushi Mehta <mehta.aaru20@gmail.com> +M: Julia Suvorova <jusual@redhat.com> +M: Stefan Hajnoczi <stefanha@redhat.com> +L: qemu-block@nongnu.org +S: Maintained +F: block/io_uring.c + qcow2 M: Kevin Wolf <kwolf@redhat.com> M: Max Reitz <mreitz@redhat.com> diff --git a/block/Makefile.objs b/block/Makefile.objs index 330529b0b7..3bcb35c81d 100644 --- a/block/Makefile.objs +++ b/block/Makefile.objs @@ -18,6 +18,7 @@ block-obj-y += block-backend.o snapshot.o qapi.o block-obj-$(CONFIG_WIN32) += file-win32.o win32-aio.o block-obj-$(CONFIG_POSIX) += file-posix.o block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o +block-obj-$(CONFIG_LINUX_IO_URING) += io_uring.o block-obj-y += null.o mirror.o commit.o io.o create.o block-obj-y += throttle-groups.o block-obj-$(CONFIG_LINUX) += nvme.o @@ -66,5 +67,7 @@ block-obj-$(if $(CONFIG_LZFSE),m,n) += dmg-lzfse.o dmg-lzfse.o-libs := $(LZFSE_LIBS) qcow.o-libs := -lz linux-aio.o-libs := -laio +io_uring.o-cflags := $(LINUX_IO_URING_CFLAGS) +io_uring.o-libs := $(LINUX_IO_URING_LIBS) parallels.o-cflags := $(LIBXML2_CFLAGS) parallels.o-libs := $(LIBXML2_LIBS) diff --git a/block/io_uring.c b/block/io_uring.c new file mode 100644 index 0000000000..bb433a685b --- /dev/null +++ b/block/io_uring.c @@ -0,0 +1,401 @@ +/* + * Linux io_uring support. + * + * Copyright (C) 2009 IBM, Corp. + * Copyright (C) 2009 Red Hat, Inc. + * Copyright (C) 2019 Aarushi Mehta + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ +#include "qemu/osdep.h" +#include <liburing.h> +#include "qemu-common.h" +#include "block/aio.h" +#include "qemu/queue.h" +#include "block/block.h" +#include "block/raw-aio.h" +#include "qemu/coroutine.h" +#include "qapi/error.h" + +/* io_uring ring size */ +#define MAX_ENTRIES 128 + +typedef struct LuringAIOCB { + Coroutine *co; + struct io_uring_sqe sqeq; + ssize_t ret; + QEMUIOVector *qiov; + bool is_read; + QSIMPLEQ_ENTRY(LuringAIOCB) next; + + /* + * Buffered reads may require resubmission, see + * luring_resubmit_short_read(). + */ + int total_read; + QEMUIOVector resubmit_qiov; +} LuringAIOCB; + +typedef struct LuringQueue { + int plugged; + unsigned int in_queue; + unsigned int in_flight; + bool blocked; + QSIMPLEQ_HEAD(, LuringAIOCB) submit_queue; +} LuringQueue; + +typedef struct LuringState { + AioContext *aio_context; + + struct io_uring ring; + + /* io queue for submit at batch. Protected by AioContext lock. */ + LuringQueue io_q; + + /* I/O completion processing. Only runs in I/O thread. */ + QEMUBH *completion_bh; +} LuringState; + +/** + * luring_resubmit: + * + * Resubmit a request by appending it to submit_queue. The caller must ensure + * that ioq_submit() is called later so that submit_queue requests are started. + */ +static void luring_resubmit(LuringState *s, LuringAIOCB *luringcb) +{ + QSIMPLEQ_INSERT_TAIL(&s->io_q.submit_queue, luringcb, next); + s->io_q.in_queue++; +} + +/** + * luring_resubmit_short_read: + * + * Before Linux commit 9d93a3f5a0c ("io_uring: punt short reads to async + * context") a buffered I/O request with the start of the file range in the + * page cache could result in a short read. Applications need to resubmit the + * remaining read request. + * + * This is a slow path but recent kernels never take it. + */ +static void luring_resubmit_short_read(LuringState *s, LuringAIOCB *luringcb, + int nread) +{ + QEMUIOVector *resubmit_qiov; + size_t remaining; + + /* Update read position */ + luringcb->total_read = nread; + remaining = luringcb->qiov->size - luringcb->total_read; + + /* Shorten qiov */ + resubmit_qiov = &luringcb->resubmit_qiov; + if (resubmit_qiov->iov == NULL) { + qemu_iovec_init(resubmit_qiov, luringcb->qiov->niov); + } else { + qemu_iovec_reset(resubmit_qiov); + } + qemu_iovec_concat(resubmit_qiov, luringcb->qiov, luringcb->total_read, + remaining); + + /* Update sqe */ + luringcb->sqeq.off = nread; + luringcb->sqeq.addr = (__u64)(uintptr_t)luringcb->resubmit_qiov.iov; + luringcb->sqeq.len = luringcb->resubmit_qiov.niov; + + luring_resubmit(s, luringcb); +} + +/** + * luring_process_completions: + * @s: AIO state + * + * Fetches completed I/O requests, consumes cqes and invokes their callbacks + * The function is somewhat tricky because it supports nested event loops, for + * example when a request callback invokes aio_poll(). + * + * Function schedules BH completion so it can be called again in a nested + * event loop. When there are no events left to complete the BH is being + * canceled. + * + */ +static void luring_process_completions(LuringState *s) +{ + struct io_uring_cqe *cqes; + int total_bytes; + /* + * Request completion callbacks can run the nested event loop. + * Schedule ourselves so the nested event loop will "see" remaining + * completed requests and process them. Without this, completion + * callbacks that wait for other requests using a nested event loop + * would hang forever. + * + * This workaround is needed because io_uring uses poll_wait, which + * is woken up when new events are added to the uring, thus polling on + * the same uring fd will block unless more events are received. + * + * Other leaf block drivers (drivers that access the data themselves) + * are networking based, so they poll sockets for data and run the + * correct coroutine. + */ + qemu_bh_schedule(s->completion_bh); + + while (io_uring_peek_cqe(&s->ring, &cqes) == 0) { + LuringAIOCB *luringcb; + int ret; + + if (!cqes) { + break; + } + + luringcb = io_uring_cqe_get_data(cqes); + ret = cqes->res; + io_uring_cqe_seen(&s->ring, cqes); + cqes = NULL; + + /* Change counters one-by-one because we can be nested. */ + s->io_q.in_flight--; + + /* total_read is non-zero only for resubmitted read requests */ + total_bytes = ret + luringcb->total_read; + + if (ret < 0) { + if (ret == -EINTR) { + luring_resubmit(s, luringcb); + continue; + } + } else if (!luringcb->qiov) { + goto end; + } else if (total_bytes == luringcb->qiov->size) { + ret = 0; + /* Only read/write */ + } else { + /* Short Read/Write */ + if (luringcb->is_read) { + if (ret > 0) { + luring_resubmit_short_read(s, luringcb, ret); + continue; + } else { + /* Pad with zeroes */ + qemu_iovec_memset(luringcb->qiov, total_bytes, 0, + luringcb->qiov->size - total_bytes); + ret = 0; + } + } else { + ret = -ENOSPC;; + } + } +end: + luringcb->ret = ret; + qemu_iovec_destroy(&luringcb->resubmit_qiov); + + /* + * If the coroutine is already entered it must be in ioq_submit() + * and will notice luringcb->ret has been filled in when it + * eventually runs later. Coroutines cannot be entered recursively + * so avoid doing that! + */ + if (!qemu_coroutine_entered(luringcb->co)) { + aio_co_wake(luringcb->co); + } + } + qemu_bh_cancel(s->completion_bh); +} + +static int ioq_submit(LuringState *s) +{ + int ret = 0; + LuringAIOCB *luringcb, *luringcb_next; + + while (s->io_q.in_queue > 0) { + /* + * Try to fetch sqes from the ring for requests waiting in + * the overflow queue + */ + QSIMPLEQ_FOREACH_SAFE(luringcb, &s->io_q.submit_queue, next, + luringcb_next) { + struct io_uring_sqe *sqes = io_uring_get_sqe(&s->ring); + if (!sqes) { + break; + } + /* Prep sqe for submission */ + *sqes = luringcb->sqeq; + QSIMPLEQ_REMOVE_HEAD(&s->io_q.submit_queue, next); + } + ret = io_uring_submit(&s->ring); + /* Prevent infinite loop if submission is refused */ + if (ret <= 0) { + if (ret == -EAGAIN) { + continue; + } + break; + } + s->io_q.in_flight += ret; + s->io_q.in_queue -= ret; + } + s->io_q.blocked = (s->io_q.in_queue > 0); + + if (s->io_q.in_flight) { + /* + * We can try to complete something just right away if there are + * still requests in-flight. + */ + luring_process_completions(s); + } + return ret; +} + +static void luring_process_completions_and_submit(LuringState *s) +{ + aio_context_acquire(s->aio_context); + luring_process_completions(s); + + if (!s->io_q.plugged && s->io_q.in_queue > 0) { + ioq_submit(s); + } + aio_context_release(s->aio_context); +} + +static void qemu_luring_completion_bh(void *opaque) +{ + LuringState *s = opaque; + luring_process_completions_and_submit(s); +} + +static void qemu_luring_completion_cb(void *opaque) +{ + LuringState *s = opaque; + luring_process_completions_and_submit(s); +} + +static void ioq_init(LuringQueue *io_q) +{ + QSIMPLEQ_INIT(&io_q->submit_queue); + io_q->plugged = 0; + io_q->in_queue = 0; + io_q->in_flight = 0; + io_q->blocked = false; +} + +void luring_io_plug(BlockDriverState *bs, LuringState *s) +{ + s->io_q.plugged++; +} + +void luring_io_unplug(BlockDriverState *bs, LuringState *s) +{ + assert(s->io_q.plugged); + if (--s->io_q.plugged == 0 && + !s->io_q.blocked && s->io_q.in_queue > 0) { + ioq_submit(s); + } +} + +/** + * luring_do_submit: + * @fd: file descriptor for I/O + * @luringcb: AIO control block + * @s: AIO state + * @offset: offset for request + * @type: type of request + * + * Fetches sqes from ring, adds to pending queue and preps them + * + */ +static int luring_do_submit(int fd, LuringAIOCB *luringcb, LuringState *s, + uint64_t offset, int type) +{ + struct io_uring_sqe *sqes = &luringcb->sqeq; + + switch (type) { + case QEMU_AIO_WRITE: + io_uring_prep_writev(sqes, fd, luringcb->qiov->iov, + luringcb->qiov->niov, offset); + break; + case QEMU_AIO_READ: + io_uring_prep_readv(sqes, fd, luringcb->qiov->iov, + luringcb->qiov->niov, offset); + break; + case QEMU_AIO_FLUSH: + io_uring_prep_fsync(sqes, fd, IORING_FSYNC_DATASYNC); + break; + default: + fprintf(stderr, "%s: invalid AIO request type, aborting 0x%x.\n", + __func__, type); + abort(); + } + io_uring_sqe_set_data(sqes, luringcb); + + QSIMPLEQ_INSERT_TAIL(&s->io_q.submit_queue, luringcb, next); + s->io_q.in_queue++; + + if (!s->io_q.blocked && + (!s->io_q.plugged || + s->io_q.in_flight + s->io_q.in_queue >= MAX_ENTRIES)) { + return ioq_submit(s); + } + return 0; +} + +int coroutine_fn luring_co_submit(BlockDriverState *bs, LuringState *s, int fd, + uint64_t offset, QEMUIOVector *qiov, int type) +{ + int ret; + LuringAIOCB luringcb = { + .co = qemu_coroutine_self(), + .ret = -EINPROGRESS, + .qiov = qiov, + .is_read = (type == QEMU_AIO_READ), + }; + + ret = luring_do_submit(fd, &luringcb, s, offset, type); + if (ret < 0) { + return ret; + } + + if (luringcb.ret == -EINPROGRESS) { + qemu_coroutine_yield(); + } + return luringcb.ret; +} + +void luring_detach_aio_context(LuringState *s, AioContext *old_context) +{ + aio_set_fd_handler(old_context, s->ring.ring_fd, false, NULL, NULL, NULL, + s); + qemu_bh_delete(s->completion_bh); + s->aio_context = NULL; +} + +void luring_attach_aio_context(LuringState *s, AioContext *new_context) +{ + s->aio_context = new_context; + s->completion_bh = aio_bh_new(new_context, qemu_luring_completion_bh, s); + aio_set_fd_handler(s->aio_context, s->ring.ring_fd, false, + qemu_luring_completion_cb, NULL, NULL, s); +} + +LuringState *luring_init(Error **errp) +{ + int rc; + LuringState *s = g_new0(LuringState, 1); + struct io_uring *ring = &s->ring; + + rc = io_uring_queue_init(MAX_ENTRIES, ring, 0); + if (rc < 0) { + error_setg_errno(errp, errno, "failed to init linux io_uring ring"); + g_free(s); + return NULL; + } + + ioq_init(&s->io_q); + return s; + +} + +void luring_cleanup(LuringState *s) +{ + io_uring_queue_exit(&s->ring); + g_free(s); +} diff --git a/include/block/aio.h b/include/block/aio.h index 6b0d52f732..7ba9bd7874 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -49,6 +49,7 @@ typedef void IOHandler(void *opaque); struct Coroutine; struct ThreadPool; struct LinuxAioState; +struct LuringState; struct AioContext { GSource source; @@ -117,11 +118,19 @@ struct AioContext { struct ThreadPool *thread_pool; #ifdef CONFIG_LINUX_AIO - /* State for native Linux AIO. Uses aio_context_acquire/release for + /* + * State for native Linux AIO. Uses aio_context_acquire/release for * locking. */ struct LinuxAioState *linux_aio; #endif +#ifdef CONFIG_LINUX_IO_URING + /* + * State for Linux io_uring. Uses aio_context_acquire/release for + * locking. + */ + struct LuringState *linux_io_uring; +#endif /* TimerLists for calling timers - one per clock type. Has its own * locking. @@ -386,6 +395,11 @@ struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp); /* Return the LinuxAioState bound to this AioContext */ struct LinuxAioState *aio_get_linux_aio(AioContext *ctx); +/* Setup the LuringState bound to this AioContext */ +struct LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp); + +/* Return the LuringState bound to this AioContext */ +struct LuringState *aio_get_linux_io_uring(AioContext *ctx); /** * aio_timer_new_with_attrs: * @ctx: the aio context diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h index 4629f24d08..251b10d273 100644 --- a/include/block/raw-aio.h +++ b/include/block/raw-aio.h @@ -57,6 +57,18 @@ void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context); void laio_io_plug(BlockDriverState *bs, LinuxAioState *s); void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s); #endif +/* io_uring.c - Linux io_uring implementation */ +#ifdef CONFIG_LINUX_IO_URING +typedef struct LuringState LuringState; +LuringState *luring_init(Error **errp); +void luring_cleanup(LuringState *s); +int coroutine_fn luring_co_submit(BlockDriverState *bs, LuringState *s, int fd, + uint64_t offset, QEMUIOVector *qiov, int type); +void luring_detach_aio_context(LuringState *s, AioContext *old_context); +void luring_attach_aio_context(LuringState *s, AioContext *new_context); +void luring_io_plug(BlockDriverState *bs, LuringState *s); +void luring_io_unplug(BlockDriverState *bs, LuringState *s); +#endif #ifdef _WIN32 typedef struct QEMUWin32AIOState QEMUWin32AIOState; |