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Diffstat (limited to 'include/block/aio.h')
-rw-r--r-- | include/block/aio.h | 770 |
1 files changed, 770 insertions, 0 deletions
diff --git a/include/block/aio.h b/include/block/aio.h new file mode 100644 index 000000000..47fbe9d81 --- /dev/null +++ b/include/block/aio.h @@ -0,0 +1,770 @@ +/* + * QEMU aio implementation + * + * Copyright IBM, Corp. 2008 + * + * Authors: + * Anthony Liguori <aliguori@us.ibm.com> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + */ + +#ifndef QEMU_AIO_H +#define QEMU_AIO_H + +#ifdef CONFIG_LINUX_IO_URING +#include <liburing.h> +#endif +#include "qemu/coroutine.h" +#include "qemu/queue.h" +#include "qemu/event_notifier.h" +#include "qemu/thread.h" +#include "qemu/timer.h" + +typedef struct BlockAIOCB BlockAIOCB; +typedef void BlockCompletionFunc(void *opaque, int ret); + +typedef struct AIOCBInfo { + void (*cancel_async)(BlockAIOCB *acb); + AioContext *(*get_aio_context)(BlockAIOCB *acb); + size_t aiocb_size; +} AIOCBInfo; + +struct BlockAIOCB { + const AIOCBInfo *aiocb_info; + BlockDriverState *bs; + BlockCompletionFunc *cb; + void *opaque; + int refcnt; +}; + +void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs, + BlockCompletionFunc *cb, void *opaque); +void qemu_aio_unref(void *p); +void qemu_aio_ref(void *p); + +typedef struct AioHandler AioHandler; +typedef QLIST_HEAD(, AioHandler) AioHandlerList; +typedef void QEMUBHFunc(void *opaque); +typedef bool AioPollFn(void *opaque); +typedef void IOHandler(void *opaque); + +struct Coroutine; +struct ThreadPool; +struct LinuxAioState; +struct LuringState; + +/* Is polling disabled? */ +bool aio_poll_disabled(AioContext *ctx); + +/* Callbacks for file descriptor monitoring implementations */ +typedef struct { + /* + * update: + * @ctx: the AioContext + * @old_node: the existing handler or NULL if this file descriptor is being + * monitored for the first time + * @new_node: the new handler or NULL if this file descriptor is being + * removed + * + * Add/remove/modify a monitored file descriptor. + * + * Called with ctx->list_lock acquired. + */ + void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node); + + /* + * wait: + * @ctx: the AioContext + * @ready_list: list for handlers that become ready + * @timeout: maximum duration to wait, in nanoseconds + * + * Wait for file descriptors to become ready and place them on ready_list. + * + * Called with ctx->list_lock incremented but not locked. + * + * Returns: number of ready file descriptors. + */ + int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout); + + /* + * need_wait: + * @ctx: the AioContext + * + * Tell aio_poll() when to stop userspace polling early because ->wait() + * has fds ready. + * + * File descriptor monitoring implementations that cannot poll fd readiness + * from userspace should use aio_poll_disabled() here. This ensures that + * file descriptors are not starved by handlers that frequently make + * progress via userspace polling. + * + * Returns: true if ->wait() should be called, false otherwise. + */ + bool (*need_wait)(AioContext *ctx); +} FDMonOps; + +/* + * Each aio_bh_poll() call carves off a slice of the BH list, so that newly + * scheduled BHs are not processed until the next aio_bh_poll() call. All + * active aio_bh_poll() calls chain their slices together in a list, so that + * nested aio_bh_poll() calls process all scheduled bottom halves. + */ +typedef QSLIST_HEAD(, QEMUBH) BHList; +typedef struct BHListSlice BHListSlice; +struct BHListSlice { + BHList bh_list; + QSIMPLEQ_ENTRY(BHListSlice) next; +}; + +typedef QSLIST_HEAD(, AioHandler) AioHandlerSList; + +struct AioContext { + GSource source; + + /* Used by AioContext users to protect from multi-threaded access. */ + QemuRecMutex lock; + + /* The list of registered AIO handlers. Protected by ctx->list_lock. */ + AioHandlerList aio_handlers; + + /* The list of AIO handlers to be deleted. Protected by ctx->list_lock. */ + AioHandlerList deleted_aio_handlers; + + /* Used to avoid unnecessary event_notifier_set calls in aio_notify; + * only written from the AioContext home thread, or under the BQL in + * the case of the main AioContext. However, it is read from any + * thread so it is still accessed with atomic primitives. + * + * If this field is 0, everything (file descriptors, bottom halves, + * timers) will be re-evaluated before the next blocking poll() or + * io_uring wait; therefore, the event_notifier_set call can be + * skipped. If it is non-zero, you may need to wake up a concurrent + * aio_poll or the glib main event loop, making event_notifier_set + * necessary. + * + * Bit 0 is reserved for GSource usage of the AioContext, and is 1 + * between a call to aio_ctx_prepare and the next call to aio_ctx_check. + * Bits 1-31 simply count the number of active calls to aio_poll + * that are in the prepare or poll phase. + * + * The GSource and aio_poll must use a different mechanism because + * there is no certainty that a call to GSource's prepare callback + * (via g_main_context_prepare) is indeed followed by check and + * dispatch. It's not clear whether this would be a bug, but let's + * play safe and allow it---it will just cause extra calls to + * event_notifier_set until the next call to dispatch. + * + * Instead, the aio_poll calls include both the prepare and the + * dispatch phase, hence a simple counter is enough for them. + */ + uint32_t notify_me; + + /* A lock to protect between QEMUBH and AioHandler adders and deleter, + * and to ensure that no callbacks are removed while we're walking and + * dispatching them. + */ + QemuLockCnt list_lock; + + /* Bottom Halves pending aio_bh_poll() processing */ + BHList bh_list; + + /* Chained BH list slices for each nested aio_bh_poll() call */ + QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list; + + /* Used by aio_notify. + * + * "notified" is used to avoid expensive event_notifier_test_and_clear + * calls. When it is clear, the EventNotifier is clear, or one thread + * is going to clear "notified" before processing more events. False + * positives are possible, i.e. "notified" could be set even though the + * EventNotifier is clear. + * + * Note that event_notifier_set *cannot* be optimized the same way. For + * more information on the problem that would result, see "#ifdef BUG2" + * in the docs/aio_notify_accept.promela formal model. + */ + bool notified; + EventNotifier notifier; + + QSLIST_HEAD(, Coroutine) scheduled_coroutines; + QEMUBH *co_schedule_bh; + + /* Thread pool for performing work and receiving completion callbacks. + * Has its own locking. + */ + struct ThreadPool *thread_pool; + +#ifdef CONFIG_LINUX_AIO + /* + * 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; + + /* State for file descriptor monitoring using Linux io_uring */ + struct io_uring fdmon_io_uring; + AioHandlerSList submit_list; +#endif + + /* TimerLists for calling timers - one per clock type. Has its own + * locking. + */ + QEMUTimerListGroup tlg; + + int external_disable_cnt; + + /* Number of AioHandlers without .io_poll() */ + int poll_disable_cnt; + + /* Polling mode parameters */ + int64_t poll_ns; /* current polling time in nanoseconds */ + int64_t poll_max_ns; /* maximum polling time in nanoseconds */ + int64_t poll_grow; /* polling time growth factor */ + int64_t poll_shrink; /* polling time shrink factor */ + + /* AIO engine parameters */ + int64_t aio_max_batch; /* maximum number of requests in a batch */ + + /* + * List of handlers participating in userspace polling. Protected by + * ctx->list_lock. Iterated and modified mostly by the event loop thread + * from aio_poll() with ctx->list_lock incremented. aio_set_fd_handler() + * only touches the list to delete nodes if ctx->list_lock's count is zero. + */ + AioHandlerList poll_aio_handlers; + + /* Are we in polling mode or monitoring file descriptors? */ + bool poll_started; + + /* epoll(7) state used when built with CONFIG_EPOLL */ + int epollfd; + + const FDMonOps *fdmon_ops; +}; + +/** + * aio_context_new: Allocate a new AioContext. + * + * AioContext provide a mini event-loop that can be waited on synchronously. + * They also provide bottom halves, a service to execute a piece of code + * as soon as possible. + */ +AioContext *aio_context_new(Error **errp); + +/** + * aio_context_ref: + * @ctx: The AioContext to operate on. + * + * Add a reference to an AioContext. + */ +void aio_context_ref(AioContext *ctx); + +/** + * aio_context_unref: + * @ctx: The AioContext to operate on. + * + * Drop a reference to an AioContext. + */ +void aio_context_unref(AioContext *ctx); + +/* Take ownership of the AioContext. If the AioContext will be shared between + * threads, and a thread does not want to be interrupted, it will have to + * take ownership around calls to aio_poll(). Otherwise, aio_poll() + * automatically takes care of calling aio_context_acquire and + * aio_context_release. + * + * Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A + * thread still has to call those to avoid being interrupted by the guest. + * + * Bottom halves, timers and callbacks can be created or removed without + * acquiring the AioContext. + */ +void aio_context_acquire(AioContext *ctx); + +/* Relinquish ownership of the AioContext. */ +void aio_context_release(AioContext *ctx); + +/** + * aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will + * run only once and as soon as possible. + * + * @name: A human-readable identifier for debugging purposes. + */ +void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name); + +/** + * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run + * only once and as soon as possible. + * + * A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the + * name string. + */ +#define aio_bh_schedule_oneshot(ctx, cb, opaque) \ + aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb))) + +/** + * aio_bh_new_full: Allocate a new bottom half structure. + * + * Bottom halves are lightweight callbacks whose invocation is guaranteed + * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure + * is opaque and must be allocated prior to its use. + * + * @name: A human-readable identifier for debugging purposes. + */ +QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name); + +/** + * aio_bh_new: Allocate a new bottom half structure + * + * A convenience wrapper for aio_bh_new_full() that uses the cb as the name + * string. + */ +#define aio_bh_new(ctx, cb, opaque) \ + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb))) + +/** + * aio_notify: Force processing of pending events. + * + * Similar to signaling a condition variable, aio_notify forces + * aio_poll to exit, so that the next call will re-examine pending events. + * The caller of aio_notify will usually call aio_poll again very soon, + * or go through another iteration of the GLib main loop. Hence, aio_notify + * also has the side effect of recalculating the sets of file descriptors + * that the main loop waits for. + * + * Calling aio_notify is rarely necessary, because for example scheduling + * a bottom half calls it already. + */ +void aio_notify(AioContext *ctx); + +/** + * aio_notify_accept: Acknowledge receiving an aio_notify. + * + * aio_notify() uses an EventNotifier in order to wake up a sleeping + * aio_poll() or g_main_context_iteration(). Calls to aio_notify() are + * usually rare, but the AioContext has to clear the EventNotifier on + * every aio_poll() or g_main_context_iteration() in order to avoid + * busy waiting. This event_notifier_test_and_clear() cannot be done + * using the usual aio_context_set_event_notifier(), because it must + * be done before processing all events (file descriptors, bottom halves, + * timers). + * + * aio_notify_accept() is an optimized event_notifier_test_and_clear() + * that is specific to an AioContext's notifier; it is used internally + * to clear the EventNotifier only if aio_notify() had been called. + */ +void aio_notify_accept(AioContext *ctx); + +/** + * aio_bh_call: Executes callback function of the specified BH. + */ +void aio_bh_call(QEMUBH *bh); + +/** + * aio_bh_poll: Poll bottom halves for an AioContext. + * + * These are internal functions used by the QEMU main loop. + * And notice that multiple occurrences of aio_bh_poll cannot + * be called concurrently + */ +int aio_bh_poll(AioContext *ctx); + +/** + * qemu_bh_schedule: Schedule a bottom half. + * + * Scheduling a bottom half interrupts the main loop and causes the + * execution of the callback that was passed to qemu_bh_new. + * + * Bottom halves that are scheduled from a bottom half handler are instantly + * invoked. This can create an infinite loop if a bottom half handler + * schedules itself. + * + * @bh: The bottom half to be scheduled. + */ +void qemu_bh_schedule(QEMUBH *bh); + +/** + * qemu_bh_cancel: Cancel execution of a bottom half. + * + * Canceling execution of a bottom half undoes the effect of calls to + * qemu_bh_schedule without freeing its resources yet. While cancellation + * itself is also wait-free and thread-safe, it can of course race with the + * loop that executes bottom halves unless you are holding the iothread + * mutex. This makes it mostly useless if you are not holding the mutex. + * + * @bh: The bottom half to be canceled. + */ +void qemu_bh_cancel(QEMUBH *bh); + +/** + *qemu_bh_delete: Cancel execution of a bottom half and free its resources. + * + * Deleting a bottom half frees the memory that was allocated for it by + * qemu_bh_new. It also implies canceling the bottom half if it was + * scheduled. + * This func is async. The bottom half will do the delete action at the finial + * end. + * + * @bh: The bottom half to be deleted. + */ +void qemu_bh_delete(QEMUBH *bh); + +/* Return whether there are any pending callbacks from the GSource + * attached to the AioContext, before g_poll is invoked. + * + * This is used internally in the implementation of the GSource. + */ +bool aio_prepare(AioContext *ctx); + +/* Return whether there are any pending callbacks from the GSource + * attached to the AioContext, after g_poll is invoked. + * + * This is used internally in the implementation of the GSource. + */ +bool aio_pending(AioContext *ctx); + +/* Dispatch any pending callbacks from the GSource attached to the AioContext. + * + * This is used internally in the implementation of the GSource. + */ +void aio_dispatch(AioContext *ctx); + +/* Progress in completing AIO work to occur. This can issue new pending + * aio as a result of executing I/O completion or bh callbacks. + * + * Return whether any progress was made by executing AIO or bottom half + * handlers. If @blocking == true, this should always be true except + * if someone called aio_notify. + * + * If there are no pending bottom halves, but there are pending AIO + * operations, it may not be possible to make any progress without + * blocking. If @blocking is true, this function will wait until one + * or more AIO events have completed, to ensure something has moved + * before returning. + */ +bool aio_poll(AioContext *ctx, bool blocking); + +/* Register a file descriptor and associated callbacks. Behaves very similarly + * to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will + * be invoked when using aio_poll(). + * + * Code that invokes AIO completion functions should rely on this function + * instead of qemu_set_fd_handler[2]. + */ +void aio_set_fd_handler(AioContext *ctx, + int fd, + bool is_external, + IOHandler *io_read, + IOHandler *io_write, + AioPollFn *io_poll, + void *opaque); + +/* Set polling begin/end callbacks for a file descriptor that has already been + * registered with aio_set_fd_handler. Do nothing if the file descriptor is + * not registered. + */ +void aio_set_fd_poll(AioContext *ctx, int fd, + IOHandler *io_poll_begin, + IOHandler *io_poll_end); + +/* Register an event notifier and associated callbacks. Behaves very similarly + * to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks + * will be invoked when using aio_poll(). + * + * Code that invokes AIO completion functions should rely on this function + * instead of event_notifier_set_handler. + */ +void aio_set_event_notifier(AioContext *ctx, + EventNotifier *notifier, + bool is_external, + EventNotifierHandler *io_read, + AioPollFn *io_poll); + +/* Set polling begin/end callbacks for an event notifier that has already been + * registered with aio_set_event_notifier. Do nothing if the event notifier is + * not registered. + */ +void aio_set_event_notifier_poll(AioContext *ctx, + EventNotifier *notifier, + EventNotifierHandler *io_poll_begin, + EventNotifierHandler *io_poll_end); + +/* Return a GSource that lets the main loop poll the file descriptors attached + * to this AioContext. + */ +GSource *aio_get_g_source(AioContext *ctx); + +/* Return the ThreadPool bound to this AioContext */ +struct ThreadPool *aio_get_thread_pool(AioContext *ctx); + +/* Setup the LinuxAioState bound to this AioContext */ +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 + * @type: the clock type + * @scale: the scale + * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values + * to assign + * @cb: the callback to call on timer expiry + * @opaque: the opaque pointer to pass to the callback + * + * Allocate a new timer (with attributes) attached to the context @ctx. + * The function is responsible for memory allocation. + * + * The preferred interface is aio_timer_init or aio_timer_init_with_attrs. + * Use that unless you really need dynamic memory allocation. + * + * Returns: a pointer to the new timer + */ +static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx, + QEMUClockType type, + int scale, int attributes, + QEMUTimerCB *cb, void *opaque) +{ + return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque); +} + +/** + * aio_timer_new: + * @ctx: the aio context + * @type: the clock type + * @scale: the scale + * @cb: the callback to call on timer expiry + * @opaque: the opaque pointer to pass to the callback + * + * Allocate a new timer attached to the context @ctx. + * See aio_timer_new_with_attrs for details. + * + * Returns: a pointer to the new timer + */ +static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type, + int scale, + QEMUTimerCB *cb, void *opaque) +{ + return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque); +} + +/** + * aio_timer_init_with_attrs: + * @ctx: the aio context + * @ts: the timer + * @type: the clock type + * @scale: the scale + * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values + * to assign + * @cb: the callback to call on timer expiry + * @opaque: the opaque pointer to pass to the callback + * + * Initialise a new timer (with attributes) attached to the context @ctx. + * The caller is responsible for memory allocation. + */ +static inline void aio_timer_init_with_attrs(AioContext *ctx, + QEMUTimer *ts, QEMUClockType type, + int scale, int attributes, + QEMUTimerCB *cb, void *opaque) +{ + timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque); +} + +/** + * aio_timer_init: + * @ctx: the aio context + * @ts: the timer + * @type: the clock type + * @scale: the scale + * @cb: the callback to call on timer expiry + * @opaque: the opaque pointer to pass to the callback + * + * Initialise a new timer attached to the context @ctx. + * See aio_timer_init_with_attrs for details. + */ +static inline void aio_timer_init(AioContext *ctx, + QEMUTimer *ts, QEMUClockType type, + int scale, + QEMUTimerCB *cb, void *opaque) +{ + timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque); +} + +/** + * aio_compute_timeout: + * @ctx: the aio context + * + * Compute the timeout that a blocking aio_poll should use. + */ +int64_t aio_compute_timeout(AioContext *ctx); + +/** + * aio_disable_external: + * @ctx: the aio context + * + * Disable the further processing of external clients. + */ +static inline void aio_disable_external(AioContext *ctx) +{ + qatomic_inc(&ctx->external_disable_cnt); +} + +/** + * aio_enable_external: + * @ctx: the aio context + * + * Enable the processing of external clients. + */ +static inline void aio_enable_external(AioContext *ctx) +{ + int old; + + old = qatomic_fetch_dec(&ctx->external_disable_cnt); + assert(old > 0); + if (old == 1) { + /* Kick event loop so it re-arms file descriptors */ + aio_notify(ctx); + } +} + +/** + * aio_external_disabled: + * @ctx: the aio context + * + * Return true if the external clients are disabled. + */ +static inline bool aio_external_disabled(AioContext *ctx) +{ + return qatomic_read(&ctx->external_disable_cnt); +} + +/** + * aio_node_check: + * @ctx: the aio context + * @is_external: Whether or not the checked node is an external event source. + * + * Check if the node's is_external flag is okay to be polled by the ctx at this + * moment. True means green light. + */ +static inline bool aio_node_check(AioContext *ctx, bool is_external) +{ + return !is_external || !qatomic_read(&ctx->external_disable_cnt); +} + +/** + * aio_co_schedule: + * @ctx: the aio context + * @co: the coroutine + * + * Start a coroutine on a remote AioContext. + * + * The coroutine must not be entered by anyone else while aio_co_schedule() + * is active. In addition the coroutine must have yielded unless ctx + * is the context in which the coroutine is running (i.e. the value of + * qemu_get_current_aio_context() from the coroutine itself). + */ +void aio_co_schedule(AioContext *ctx, struct Coroutine *co); + +/** + * aio_co_reschedule_self: + * @new_ctx: the new context + * + * Move the currently running coroutine to new_ctx. If the coroutine is already + * running in new_ctx, do nothing. + */ +void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx); + +/** + * aio_co_wake: + * @co: the coroutine + * + * Restart a coroutine on the AioContext where it was running last, thus + * preventing coroutines from jumping from one context to another when they + * go to sleep. + * + * aio_co_wake may be executed either in coroutine or non-coroutine + * context. The coroutine must not be entered by anyone else while + * aio_co_wake() is active. + */ +void aio_co_wake(struct Coroutine *co); + +/** + * aio_co_enter: + * @ctx: the context to run the coroutine + * @co: the coroutine to run + * + * Enter a coroutine in the specified AioContext. + */ +void aio_co_enter(AioContext *ctx, struct Coroutine *co); + +/** + * Return the AioContext whose event loop runs in the current thread. + * + * If called from an IOThread this will be the IOThread's AioContext. If + * called from the main thread or with the "big QEMU lock" taken it + * will be the main loop AioContext. + */ +AioContext *qemu_get_current_aio_context(void); + +void qemu_set_current_aio_context(AioContext *ctx); + +/** + * aio_context_setup: + * @ctx: the aio context + * + * Initialize the aio context. + */ +void aio_context_setup(AioContext *ctx); + +/** + * aio_context_destroy: + * @ctx: the aio context + * + * Destroy the aio context. + */ +void aio_context_destroy(AioContext *ctx); + +/* Used internally, do not call outside AioContext code */ +void aio_context_use_g_source(AioContext *ctx); + +/** + * aio_context_set_poll_params: + * @ctx: the aio context + * @max_ns: how long to busy poll for, in nanoseconds + * @grow: polling time growth factor + * @shrink: polling time shrink factor + * + * Poll mode can be disabled by setting poll_max_ns to 0. + */ +void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, + int64_t grow, int64_t shrink, + Error **errp); + +/** + * aio_context_set_aio_params: + * @ctx: the aio context + * @max_batch: maximum number of requests in a batch, 0 means that the + * engine will use its default + */ +void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch, + Error **errp); + +#endif |