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Revision b22fa62a35d7f2029d757a518d78041822b7c7c1 authored by Pavel Begunkov on 21 October 2021, 12:20:29 UTC, committed by Jens Axboe on 21 October 2021, 17:19:38 UTC 
io_uring: apply worker limits to previous users
 
Another change to the API io-wq worker limitation API added in 5.15,
apply the limit to all prior users that already registered a tctx. It
may be confusing as it's now, in particular the change covers the
following 2 cases:

TASK1                   | TASK2
_________________________________________________
ring = create()         |
                        | limit_iowq_workers()
*not limited*           |

TASK1                   | TASK2
_________________________________________________
ring = create()         |
                        | issue_requests()
limit_iowq_workers()    |
                        | *not limited*

A note on locking, it's safe to traverse ->tctx_list as we hold
->uring_lock, but do that after dropping sqd->lock to avoid possible
problems. It's also safe to access tctx->io_wq there because tasks
kill it only after removing themselves from tctx_list, see
io_uring_cancel_generic() -> io_uring_clean_tctx()

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d6e09ecc3545e4dc56e43c906ee3d71b7ae21bed.1634818641.git.asml.silence@gmail.com
Reviewed-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 parent 4ea672a
Raw File
blk-mq-virtio.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2016 Christoph Hellwig.
 */
#include <linux/device.h>
#include <linux/blk-mq.h>
#include <linux/blk-mq-virtio.h>
#include <linux/virtio_config.h>
#include <linux/module.h>
#include "blk-mq.h"

/**
 * blk_mq_virtio_map_queues - provide a default queue mapping for virtio device
 * @qmap:	CPU to hardware queue map.
 * @vdev:	virtio device to provide a mapping for.
 * @first_vec:	first interrupt vectors to use for queues (usually 0)
 *
 * This function assumes the virtio device @vdev has at least as many available
 * interrupt vectors as @set has queues.  It will then query the vector
 * corresponding to each queue for it's affinity mask and built queue mapping
 * that maps a queue to the CPUs that have irq affinity for the corresponding
 * vector.
 */
int blk_mq_virtio_map_queues(struct blk_mq_queue_map *qmap,
		struct virtio_device *vdev, int first_vec)
{
	const struct cpumask *mask;
	unsigned int queue, cpu;

	if (!vdev->config->get_vq_affinity)
		goto fallback;

	for (queue = 0; queue < qmap->nr_queues; queue++) {
		mask = vdev->config->get_vq_affinity(vdev, first_vec + queue);
		if (!mask)
			goto fallback;

		for_each_cpu(cpu, mask)
			qmap->mq_map[cpu] = qmap->queue_offset + queue;
	}

	return 0;
fallback:
	return blk_mq_map_queues(qmap);
}
EXPORT_SYMBOL_GPL(blk_mq_virtio_map_queues);
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