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The IOQueue has a pool of iocb structs and a function to add new read/write requests. Multiple requests can be added before calling the submit function to actually tell the host kernel to begin I/O. This allows callers to batch requests and submit them in one go. The actual I/O is performed using Linux AIO. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
58 lines
1.7 KiB
C
58 lines
1.7 KiB
C
/*
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* Linux AIO request queue
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*
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* Copyright 2012 IBM, Corp.
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* Copyright 2012 Red Hat, Inc. and/or its affiliates
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#ifndef IOQ_H
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#define IOQ_H
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#include <libaio.h>
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#include "qemu/event_notifier.h"
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typedef struct {
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int fd; /* file descriptor */
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unsigned int max_reqs; /* max length of freelist and queue */
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io_context_t io_ctx; /* Linux AIO context */
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EventNotifier io_notifier; /* Linux AIO eventfd */
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/* Requests can complete in any order so a free list is necessary to manage
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* available iocbs.
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*/
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struct iocb **freelist; /* free iocbs */
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unsigned int freelist_idx;
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/* Multiple requests are queued up before submitting them all in one go */
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struct iocb **queue; /* queued iocbs */
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unsigned int queue_idx;
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} IOQueue;
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void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs);
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void ioq_cleanup(IOQueue *ioq);
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EventNotifier *ioq_get_notifier(IOQueue *ioq);
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struct iocb *ioq_get_iocb(IOQueue *ioq);
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void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb);
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struct iocb *ioq_rdwr(IOQueue *ioq, bool read, struct iovec *iov,
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unsigned int count, long long offset);
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int ioq_submit(IOQueue *ioq);
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static inline unsigned int ioq_num_queued(IOQueue *ioq)
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{
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return ioq->queue_idx;
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}
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typedef void IOQueueCompletion(struct iocb *iocb, ssize_t ret, void *opaque);
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int ioq_run_completion(IOQueue *ioq, IOQueueCompletion *completion,
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void *opaque);
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#endif /* IOQ_H */
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