laio_init() can fail for a couple of reasons, which will lead to a NULL pointer dereference in laio_attach_aio_context(). To solve this, add a aio_setup_linux_aio() function which is called early in raw_open_common. If this fails, propagate the error up. The signature of aio_get_linux_aio() was not modified, because it seems preferable to return the actual errno from the possible failing initialization calls. Additionally, when the AioContext changes, we need to associate a LinuxAioState with the new AioContext. Use the bdrv_attach_aio_context callback and call the new aio_setup_linux_aio(), which will allocate a new AioContext if needed, and return errors on failures. If it fails for any reason, fallback to threaded AIO with an error message, as the device is already in-use by the guest. Add an assert that aio_get_linux_aio() cannot return NULL. Signed-off-by: Nishanth Aravamudan <naravamudan@digitalocean.com> Message-id: 20180622193700.6523-1-naravamudan@digitalocean.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
582 lines
18 KiB
C
582 lines
18 KiB
C
/*
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* QEMU aio implementation
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*
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* Copyright IBM, Corp. 2008
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef QEMU_AIO_H
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#define QEMU_AIO_H
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#include "qemu-common.h"
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#include "qemu/queue.h"
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#include "qemu/event_notifier.h"
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#include "qemu/thread.h"
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#include "qemu/timer.h"
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typedef struct BlockAIOCB BlockAIOCB;
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typedef void BlockCompletionFunc(void *opaque, int ret);
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typedef struct AIOCBInfo {
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void (*cancel_async)(BlockAIOCB *acb);
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AioContext *(*get_aio_context)(BlockAIOCB *acb);
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size_t aiocb_size;
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} AIOCBInfo;
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struct BlockAIOCB {
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const AIOCBInfo *aiocb_info;
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BlockDriverState *bs;
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BlockCompletionFunc *cb;
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void *opaque;
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int refcnt;
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};
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void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
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BlockCompletionFunc *cb, void *opaque);
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void qemu_aio_unref(void *p);
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void qemu_aio_ref(void *p);
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typedef struct AioHandler AioHandler;
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typedef void QEMUBHFunc(void *opaque);
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typedef bool AioPollFn(void *opaque);
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typedef void IOHandler(void *opaque);
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struct Coroutine;
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struct ThreadPool;
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struct LinuxAioState;
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struct AioContext {
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GSource source;
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/* Used by AioContext users to protect from multi-threaded access. */
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QemuRecMutex lock;
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/* The list of registered AIO handlers. Protected by ctx->list_lock. */
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QLIST_HEAD(, AioHandler) aio_handlers;
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/* Used to avoid unnecessary event_notifier_set calls in aio_notify;
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* accessed with atomic primitives. If this field is 0, everything
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* (file descriptors, bottom halves, timers) will be re-evaluated
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* before the next blocking poll(), thus the event_notifier_set call
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* can be skipped. If it is non-zero, you may need to wake up a
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* concurrent aio_poll or the glib main event loop, making
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* event_notifier_set necessary.
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*
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* Bit 0 is reserved for GSource usage of the AioContext, and is 1
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* between a call to aio_ctx_prepare and the next call to aio_ctx_check.
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* Bits 1-31 simply count the number of active calls to aio_poll
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* that are in the prepare or poll phase.
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*
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* The GSource and aio_poll must use a different mechanism because
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* there is no certainty that a call to GSource's prepare callback
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* (via g_main_context_prepare) is indeed followed by check and
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* dispatch. It's not clear whether this would be a bug, but let's
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* play safe and allow it---it will just cause extra calls to
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* event_notifier_set until the next call to dispatch.
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*
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* Instead, the aio_poll calls include both the prepare and the
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* dispatch phase, hence a simple counter is enough for them.
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*/
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uint32_t notify_me;
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/* A lock to protect between QEMUBH and AioHandler adders and deleter,
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* and to ensure that no callbacks are removed while we're walking and
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* dispatching them.
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*/
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QemuLockCnt list_lock;
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/* Anchor of the list of Bottom Halves belonging to the context */
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struct QEMUBH *first_bh;
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/* Used by aio_notify.
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*
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* "notified" is used to avoid expensive event_notifier_test_and_clear
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* calls. When it is clear, the EventNotifier is clear, or one thread
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* is going to clear "notified" before processing more events. False
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* positives are possible, i.e. "notified" could be set even though the
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* EventNotifier is clear.
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*
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* Note that event_notifier_set *cannot* be optimized the same way. For
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* more information on the problem that would result, see "#ifdef BUG2"
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* in the docs/aio_notify_accept.promela formal model.
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*/
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bool notified;
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EventNotifier notifier;
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QSLIST_HEAD(, Coroutine) scheduled_coroutines;
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QEMUBH *co_schedule_bh;
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/* Thread pool for performing work and receiving completion callbacks.
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* Has its own locking.
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*/
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struct ThreadPool *thread_pool;
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#ifdef CONFIG_LINUX_AIO
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/* State for native Linux AIO. Uses aio_context_acquire/release for
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* locking.
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*/
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struct LinuxAioState *linux_aio;
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#endif
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/* TimerLists for calling timers - one per clock type. Has its own
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* locking.
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*/
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QEMUTimerListGroup tlg;
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int external_disable_cnt;
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/* Number of AioHandlers without .io_poll() */
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int poll_disable_cnt;
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/* Polling mode parameters */
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int64_t poll_ns; /* current polling time in nanoseconds */
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int64_t poll_max_ns; /* maximum polling time in nanoseconds */
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int64_t poll_grow; /* polling time growth factor */
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int64_t poll_shrink; /* polling time shrink factor */
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/* Are we in polling mode or monitoring file descriptors? */
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bool poll_started;
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/* epoll(7) state used when built with CONFIG_EPOLL */
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int epollfd;
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bool epoll_enabled;
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bool epoll_available;
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};
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/**
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* aio_context_new: Allocate a new AioContext.
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*
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* AioContext provide a mini event-loop that can be waited on synchronously.
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* They also provide bottom halves, a service to execute a piece of code
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* as soon as possible.
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*/
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AioContext *aio_context_new(Error **errp);
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/**
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* aio_context_ref:
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* @ctx: The AioContext to operate on.
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*
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* Add a reference to an AioContext.
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*/
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void aio_context_ref(AioContext *ctx);
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/**
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* aio_context_unref:
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* @ctx: The AioContext to operate on.
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*
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* Drop a reference to an AioContext.
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*/
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void aio_context_unref(AioContext *ctx);
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/* Take ownership of the AioContext. If the AioContext will be shared between
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* threads, and a thread does not want to be interrupted, it will have to
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* take ownership around calls to aio_poll(). Otherwise, aio_poll()
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* automatically takes care of calling aio_context_acquire and
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* aio_context_release.
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*
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* Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A
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* thread still has to call those to avoid being interrupted by the guest.
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*
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* Bottom halves, timers and callbacks can be created or removed without
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* acquiring the AioContext.
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*/
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void aio_context_acquire(AioContext *ctx);
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/* Relinquish ownership of the AioContext. */
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void aio_context_release(AioContext *ctx);
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/**
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* aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
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* only once and as soon as possible.
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*/
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void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
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/**
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* aio_bh_new: Allocate a new bottom half structure.
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*
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* Bottom halves are lightweight callbacks whose invocation is guaranteed
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* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
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* is opaque and must be allocated prior to its use.
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*/
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QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
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/**
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* aio_notify: Force processing of pending events.
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*
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* Similar to signaling a condition variable, aio_notify forces
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* aio_poll to exit, so that the next call will re-examine pending events.
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* The caller of aio_notify will usually call aio_poll again very soon,
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* or go through another iteration of the GLib main loop. Hence, aio_notify
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* also has the side effect of recalculating the sets of file descriptors
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* that the main loop waits for.
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*
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* Calling aio_notify is rarely necessary, because for example scheduling
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* a bottom half calls it already.
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*/
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void aio_notify(AioContext *ctx);
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/**
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* aio_notify_accept: Acknowledge receiving an aio_notify.
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*
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* aio_notify() uses an EventNotifier in order to wake up a sleeping
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* aio_poll() or g_main_context_iteration(). Calls to aio_notify() are
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* usually rare, but the AioContext has to clear the EventNotifier on
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* every aio_poll() or g_main_context_iteration() in order to avoid
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* busy waiting. This event_notifier_test_and_clear() cannot be done
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* using the usual aio_context_set_event_notifier(), because it must
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* be done before processing all events (file descriptors, bottom halves,
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* timers).
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*
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* aio_notify_accept() is an optimized event_notifier_test_and_clear()
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* that is specific to an AioContext's notifier; it is used internally
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* to clear the EventNotifier only if aio_notify() had been called.
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*/
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void aio_notify_accept(AioContext *ctx);
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/**
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* aio_bh_call: Executes callback function of the specified BH.
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*/
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void aio_bh_call(QEMUBH *bh);
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/**
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* aio_bh_poll: Poll bottom halves for an AioContext.
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*
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* These are internal functions used by the QEMU main loop.
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* And notice that multiple occurrences of aio_bh_poll cannot
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* be called concurrently
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*/
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int aio_bh_poll(AioContext *ctx);
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/**
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* qemu_bh_schedule: Schedule a bottom half.
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*
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* Scheduling a bottom half interrupts the main loop and causes the
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* execution of the callback that was passed to qemu_bh_new.
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*
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* Bottom halves that are scheduled from a bottom half handler are instantly
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* invoked. This can create an infinite loop if a bottom half handler
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* schedules itself.
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*
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* @bh: The bottom half to be scheduled.
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*/
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void qemu_bh_schedule(QEMUBH *bh);
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/**
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* qemu_bh_cancel: Cancel execution of a bottom half.
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*
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* Canceling execution of a bottom half undoes the effect of calls to
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* qemu_bh_schedule without freeing its resources yet. While cancellation
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* itself is also wait-free and thread-safe, it can of course race with the
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* loop that executes bottom halves unless you are holding the iothread
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* mutex. This makes it mostly useless if you are not holding the mutex.
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*
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* @bh: The bottom half to be canceled.
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*/
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void qemu_bh_cancel(QEMUBH *bh);
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/**
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*qemu_bh_delete: Cancel execution of a bottom half and free its resources.
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*
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* Deleting a bottom half frees the memory that was allocated for it by
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* qemu_bh_new. It also implies canceling the bottom half if it was
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* scheduled.
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* This func is async. The bottom half will do the delete action at the finial
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* end.
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*
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* @bh: The bottom half to be deleted.
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*/
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void qemu_bh_delete(QEMUBH *bh);
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/* Return whether there are any pending callbacks from the GSource
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* attached to the AioContext, before g_poll is invoked.
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*
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* This is used internally in the implementation of the GSource.
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*/
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bool aio_prepare(AioContext *ctx);
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/* Return whether there are any pending callbacks from the GSource
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* attached to the AioContext, after g_poll is invoked.
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*
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* This is used internally in the implementation of the GSource.
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*/
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bool aio_pending(AioContext *ctx);
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/* Dispatch any pending callbacks from the GSource attached to the AioContext.
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*
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* This is used internally in the implementation of the GSource.
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*/
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void aio_dispatch(AioContext *ctx);
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/* Progress in completing AIO work to occur. This can issue new pending
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* aio as a result of executing I/O completion or bh callbacks.
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*
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* Return whether any progress was made by executing AIO or bottom half
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* handlers. If @blocking == true, this should always be true except
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* if someone called aio_notify.
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*
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* If there are no pending bottom halves, but there are pending AIO
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* operations, it may not be possible to make any progress without
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* blocking. If @blocking is true, this function will wait until one
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* or more AIO events have completed, to ensure something has moved
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* before returning.
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*/
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bool aio_poll(AioContext *ctx, bool blocking);
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/* Register a file descriptor and associated callbacks. Behaves very similarly
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* to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will
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* be invoked when using aio_poll().
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*
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* Code that invokes AIO completion functions should rely on this function
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* instead of qemu_set_fd_handler[2].
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*/
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void aio_set_fd_handler(AioContext *ctx,
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int fd,
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bool is_external,
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IOHandler *io_read,
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IOHandler *io_write,
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AioPollFn *io_poll,
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void *opaque);
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/* Set polling begin/end callbacks for a file descriptor that has already been
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* registered with aio_set_fd_handler. Do nothing if the file descriptor is
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* not registered.
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*/
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void aio_set_fd_poll(AioContext *ctx, int fd,
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IOHandler *io_poll_begin,
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IOHandler *io_poll_end);
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/* Register an event notifier and associated callbacks. Behaves very similarly
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* to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
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* will be invoked when using aio_poll().
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*
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* Code that invokes AIO completion functions should rely on this function
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* instead of event_notifier_set_handler.
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*/
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void aio_set_event_notifier(AioContext *ctx,
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EventNotifier *notifier,
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bool is_external,
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EventNotifierHandler *io_read,
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AioPollFn *io_poll);
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/* Set polling begin/end callbacks for an event notifier that has already been
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* registered with aio_set_event_notifier. Do nothing if the event notifier is
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* not registered.
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*/
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void aio_set_event_notifier_poll(AioContext *ctx,
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EventNotifier *notifier,
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EventNotifierHandler *io_poll_begin,
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EventNotifierHandler *io_poll_end);
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/* Return a GSource that lets the main loop poll the file descriptors attached
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* to this AioContext.
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*/
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GSource *aio_get_g_source(AioContext *ctx);
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/* Return the ThreadPool bound to this AioContext */
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struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
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/* Setup the LinuxAioState bound to this AioContext */
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struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
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/* Return the LinuxAioState bound to this AioContext */
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struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);
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/**
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* aio_timer_new:
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* @ctx: the aio context
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* @type: the clock type
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* @scale: the scale
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* @cb: the callback to call on timer expiry
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* @opaque: the opaque pointer to pass to the callback
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*
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* Allocate a new timer attached to the context @ctx.
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* The function is responsible for memory allocation.
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*
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* The preferred interface is aio_timer_init. Use that
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* unless you really need dynamic memory allocation.
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*
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* Returns: a pointer to the new timer
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*/
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static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
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int scale,
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QEMUTimerCB *cb, void *opaque)
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{
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return timer_new_tl(ctx->tlg.tl[type], scale, cb, opaque);
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}
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/**
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* aio_timer_init:
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* @ctx: the aio context
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* @ts: the timer
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* @type: the clock type
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* @scale: the scale
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* @cb: the callback to call on timer expiry
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* @opaque: the opaque pointer to pass to the callback
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*
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* Initialise a new timer attached to the context @ctx.
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* The caller is responsible for memory allocation.
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*/
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static inline void aio_timer_init(AioContext *ctx,
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QEMUTimer *ts, QEMUClockType type,
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int scale,
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QEMUTimerCB *cb, void *opaque)
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{
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timer_init_tl(ts, ctx->tlg.tl[type], scale, cb, opaque);
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}
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/**
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* aio_compute_timeout:
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* @ctx: the aio context
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*
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* Compute the timeout that a blocking aio_poll should use.
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*/
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int64_t aio_compute_timeout(AioContext *ctx);
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|
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/**
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* aio_disable_external:
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* @ctx: the aio context
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*
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* Disable the further processing of external clients.
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*/
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static inline void aio_disable_external(AioContext *ctx)
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{
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atomic_inc(&ctx->external_disable_cnt);
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}
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|
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/**
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|
* aio_enable_external:
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* @ctx: the aio context
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*
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* Enable the processing of external clients.
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*/
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static inline void aio_enable_external(AioContext *ctx)
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{
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int old;
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old = atomic_fetch_dec(&ctx->external_disable_cnt);
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assert(old > 0);
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if (old == 1) {
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/* Kick event loop so it re-arms file descriptors */
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aio_notify(ctx);
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}
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}
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/**
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* aio_external_disabled:
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* @ctx: the aio context
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*
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* Return true if the external clients are disabled.
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*/
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static inline bool aio_external_disabled(AioContext *ctx)
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{
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return atomic_read(&ctx->external_disable_cnt);
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}
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|
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/**
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|
* aio_node_check:
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* @ctx: the aio context
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|
* @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 || !atomic_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_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 another thread it will be the main loop AioContext.
|
|
*/
|
|
AioContext *qemu_get_current_aio_context(void);
|
|
|
|
/**
|
|
* in_aio_context_home_thread:
|
|
* @ctx: the aio context
|
|
*
|
|
* Return whether we are running in the thread that normally runs @ctx. Note
|
|
* that acquiring/releasing ctx does not affect the outcome, each AioContext
|
|
* still only has one home thread that is responsible for running it.
|
|
*/
|
|
static inline bool in_aio_context_home_thread(AioContext *ctx)
|
|
{
|
|
return ctx == qemu_get_current_aio_context();
|
|
}
|
|
|
|
/**
|
|
* 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);
|
|
|
|
/**
|
|
* 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);
|
|
|
|
#endif
|