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81 lines
2.8 KiB
81 lines
2.8 KiB
3 months ago
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/*
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* UCW Library -- Asynchronous I/O
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*
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* (c) 2006 Martin Mares <mj@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#ifndef _UCW_ASIO_H
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#define _UCW_ASIO_H
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#include <ucw/workqueue.h>
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#include <ucw/clists.h>
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#ifdef CONFIG_UCW_CLEAN_ABI
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#define asio_cleanup_queue ucw_asio_cleanup_queue
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#define asio_get ucw_asio_get
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#define asio_init_queue ucw_asio_init_queue
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#define asio_put ucw_asio_put
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#define asio_submit ucw_asio_submit
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#define asio_sync ucw_asio_sync
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#define asio_wait ucw_asio_wait
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#endif
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/*
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* This module takes care of scheduling and executing asynchronous I/O requests
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* on files opened with O_DIRECT. It is primarily used by the fb-direct fastbuf
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* back-end, but you can use it explicitly, too.
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*
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* You can define several I/O queues, each for use by a single thread. Requests
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* on a single queue are always processed in order of their submits, requests
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* from different queues may be interleaved (although the current implementation
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* does not do so). Normal read and write requests are returned to their queue
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* when they are completed. Write-back requests are automatically freed when
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* done, but the number of such requests in fly is limited in order to avoid
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* consuming all memory, so a submit of a write-back request can block.
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*/
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struct asio_queue {
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uint buffer_size; // How large buffers do we use [user-settable]
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uint max_writebacks; // Maximum number of writeback requests active [user-settable]
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uint allocated_requests;
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uint running_requests; // Total number of running requests
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uint running_writebacks; // How many of them are writebacks
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clist idle_list; // Recycled requests waiting for get
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clist done_list; // Finished requests
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struct work_queue queue;
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uint use_count; // For use by the caller
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};
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enum asio_op {
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ASIO_FREE,
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ASIO_READ,
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ASIO_WRITE,
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ASIO_WRITE_BACK, // Background write with no success notification
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};
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struct asio_request {
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struct work work; // asio_requests are internally just work nodes
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struct asio_queue *queue;
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byte *buffer;
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int fd;
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enum asio_op op;
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uint len;
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int status;
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int returned_errno;
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int submitted;
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void *user_data; // For use by the caller
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};
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void asio_init_queue(struct asio_queue *q); // Initialize a new queue
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void asio_cleanup_queue(struct asio_queue *q);
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struct asio_request *asio_get(struct asio_queue *q); // Get an empty request
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void asio_submit(struct asio_request *r); // Submit the request (can block if too many writebacks)
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struct asio_request *asio_wait(struct asio_queue *q); // Wait for the first finished request, NULL if no more
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void asio_put(struct asio_request *r); // Return a finished request for recycling
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void asio_sync(struct asio_queue *q); // Wait until all requests are finished
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#endif /* !_UCW_ASIO_H */
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