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man/io_uring_buf_ring_add.3
61 строка
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Jens Axboe
man/io_uring_buf_ring_add: add a note on buffer ID <-> ptr mapping
11 мар 2024, 23:43
11 мар 2024, 23:43
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.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk> .\" .\" SPDX-License-Identifier: LGPL-2.0-or-later .\" .TH io_uring_buf_ring_add 3 "May 18, 2022" "liburing-2.2" "liburing Manual" .SH NAME io_uring_buf_ring_add \- add buffers to a shared buffer ring .SH SYNOPSIS .nf .B #include <liburing.h> .PP .BI "void io_uring_buf_ring_add(struct io_uring_buf_ring *" br ", .BI " void *" addr ", .BI " unsigned int " len ", .BI " unsigned short " bid ", .BI " int " mask ", .BI " int " buf_offset ");" .fi .SH DESCRIPTION .PP The .BR io_uring_buf_ring_add (3) adds a new buffer to the shared buffer ring .IR br . The buffer address is indicated by .I addr and is of .I len bytes of length. .I bid is the buffer ID, which will be returned in the CQE. .I mask is the size mask of the ring, available from .BR io_uring_buf_ring_mask (3) . .I buf_offset is the offset to insert at from the current tail. If just one buffer is provided before the ring tail is committed with .BR io_uring_buf_ring_advance (3) or .BR io_uring_buf_ring_cq_advance (3), then .I buf_offset should be 0. If buffers are provided in a loop before being committed, the .I buf_offset must be incremented by one for each buffer added. .SH RETURN VALUE None .SH NOTES liburing (or the kernel, for that matter) doesn't care about what buffer ID maps to what buffer, and in fact when recycling buffers after use, the application is free to add a different buffer into the same buffer ID location. All that matters is that the application knows what a given buffer ID in time corresponds to in terms of virtual memory. There's no liburing or kernel assumption that these mappings are persistent over time, they can very well be different every time a given buffer ID is added to the provided buffer ring. .SH SEE ALSO .BR io_uring_register_buf_ring (3), .BR io_uring_buf_ring_mask (3), .BR io_uring_buf_ring_advance (3), .BR io_uring_buf_ring_cq_advance (3)