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![Bart Van Assche](/assets/img/avatar_default.png)
No code that occurs between blk_mq_get_ctx() and blk_mq_put_ctx() depends on preemption being disabled for its correctness. Since removing the CPU preemption calls does not measurably affect performance, simplify the blk-mq code by removing the blk_mq_put_ctx() function and also by not disabling preemption in blk_mq_get_ctx(). Cc: Hannes Reinecke <hare@suse.com> Cc: Omar Sandoval <osandov@fb.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
529 lines
14 KiB
C
529 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Tag allocation using scalable bitmaps. Uses active queue tracking to support
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* fairer distribution of tags between multiple submitters when a shared tag map
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* is used.
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*
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* Copyright (C) 2013-2014 Jens Axboe
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/blk-mq.h>
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#include "blk.h"
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#include "blk-mq.h"
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#include "blk-mq-tag.h"
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bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
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{
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if (!tags)
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return true;
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return sbitmap_any_bit_clear(&tags->bitmap_tags.sb);
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}
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/*
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* If a previously inactive queue goes active, bump the active user count.
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* We need to do this before try to allocate driver tag, then even if fail
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* to get tag when first time, the other shared-tag users could reserve
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* budget for it.
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*/
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bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
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{
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if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
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!test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
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atomic_inc(&hctx->tags->active_queues);
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return true;
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}
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/*
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* Wakeup all potentially sleeping on tags
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*/
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void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
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{
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sbitmap_queue_wake_all(&tags->bitmap_tags);
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if (include_reserve)
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sbitmap_queue_wake_all(&tags->breserved_tags);
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}
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/*
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* If a previously busy queue goes inactive, potential waiters could now
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* be allowed to queue. Wake them up and check.
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*/
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void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
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{
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struct blk_mq_tags *tags = hctx->tags;
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if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
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return;
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atomic_dec(&tags->active_queues);
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blk_mq_tag_wakeup_all(tags, false);
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}
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/*
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* For shared tag users, we track the number of currently active users
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* and attempt to provide a fair share of the tag depth for each of them.
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*/
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static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
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struct sbitmap_queue *bt)
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{
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unsigned int depth, users;
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if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
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return true;
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if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
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return true;
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/*
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* Don't try dividing an ant
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*/
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if (bt->sb.depth == 1)
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return true;
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users = atomic_read(&hctx->tags->active_queues);
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if (!users)
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return true;
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/*
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* Allow at least some tags
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*/
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depth = max((bt->sb.depth + users - 1) / users, 4U);
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return atomic_read(&hctx->nr_active) < depth;
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}
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static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
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struct sbitmap_queue *bt)
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{
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if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
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!hctx_may_queue(data->hctx, bt))
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return -1;
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if (data->shallow_depth)
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return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
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else
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return __sbitmap_queue_get(bt);
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}
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unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
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{
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struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
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struct sbitmap_queue *bt;
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struct sbq_wait_state *ws;
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DEFINE_SBQ_WAIT(wait);
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unsigned int tag_offset;
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int tag;
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if (data->flags & BLK_MQ_REQ_RESERVED) {
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if (unlikely(!tags->nr_reserved_tags)) {
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WARN_ON_ONCE(1);
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return BLK_MQ_TAG_FAIL;
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}
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bt = &tags->breserved_tags;
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tag_offset = 0;
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} else {
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bt = &tags->bitmap_tags;
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tag_offset = tags->nr_reserved_tags;
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}
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tag = __blk_mq_get_tag(data, bt);
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if (tag != -1)
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goto found_tag;
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if (data->flags & BLK_MQ_REQ_NOWAIT)
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return BLK_MQ_TAG_FAIL;
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ws = bt_wait_ptr(bt, data->hctx);
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do {
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struct sbitmap_queue *bt_prev;
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/*
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* We're out of tags on this hardware queue, kick any
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* pending IO submits before going to sleep waiting for
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* some to complete.
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*/
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blk_mq_run_hw_queue(data->hctx, false);
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/*
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* Retry tag allocation after running the hardware queue,
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* as running the queue may also have found completions.
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*/
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tag = __blk_mq_get_tag(data, bt);
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if (tag != -1)
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break;
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sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);
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tag = __blk_mq_get_tag(data, bt);
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if (tag != -1)
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break;
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bt_prev = bt;
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io_schedule();
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sbitmap_finish_wait(bt, ws, &wait);
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data->ctx = blk_mq_get_ctx(data->q);
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data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
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data->ctx);
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tags = blk_mq_tags_from_data(data);
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if (data->flags & BLK_MQ_REQ_RESERVED)
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bt = &tags->breserved_tags;
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else
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bt = &tags->bitmap_tags;
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/*
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* If destination hw queue is changed, fake wake up on
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* previous queue for compensating the wake up miss, so
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* other allocations on previous queue won't be starved.
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*/
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if (bt != bt_prev)
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sbitmap_queue_wake_up(bt_prev);
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ws = bt_wait_ptr(bt, data->hctx);
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} while (1);
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sbitmap_finish_wait(bt, ws, &wait);
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found_tag:
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return tag + tag_offset;
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}
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void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags,
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struct blk_mq_ctx *ctx, unsigned int tag)
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{
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if (!blk_mq_tag_is_reserved(tags, tag)) {
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const int real_tag = tag - tags->nr_reserved_tags;
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BUG_ON(real_tag >= tags->nr_tags);
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sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
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} else {
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BUG_ON(tag >= tags->nr_reserved_tags);
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sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
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}
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}
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struct bt_iter_data {
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struct blk_mq_hw_ctx *hctx;
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busy_iter_fn *fn;
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void *data;
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bool reserved;
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};
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static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
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{
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struct bt_iter_data *iter_data = data;
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struct blk_mq_hw_ctx *hctx = iter_data->hctx;
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struct blk_mq_tags *tags = hctx->tags;
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bool reserved = iter_data->reserved;
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struct request *rq;
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if (!reserved)
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bitnr += tags->nr_reserved_tags;
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rq = tags->rqs[bitnr];
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/*
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* We can hit rq == NULL here, because the tagging functions
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* test and set the bit before assigning ->rqs[].
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*/
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if (rq && rq->q == hctx->queue)
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return iter_data->fn(hctx, rq, iter_data->data, reserved);
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return true;
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}
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/**
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* bt_for_each - iterate over the requests associated with a hardware queue
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* @hctx: Hardware queue to examine.
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* @bt: sbitmap to examine. This is either the breserved_tags member
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* or the bitmap_tags member of struct blk_mq_tags.
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* @fn: Pointer to the function that will be called for each request
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* associated with @hctx that has been assigned a driver tag.
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* @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
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* where rq is a pointer to a request. Return true to continue
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* iterating tags, false to stop.
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* @data: Will be passed as third argument to @fn.
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* @reserved: Indicates whether @bt is the breserved_tags member or the
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* bitmap_tags member of struct blk_mq_tags.
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*/
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static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
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busy_iter_fn *fn, void *data, bool reserved)
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{
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struct bt_iter_data iter_data = {
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.hctx = hctx,
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.fn = fn,
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.data = data,
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.reserved = reserved,
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};
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sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
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}
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struct bt_tags_iter_data {
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struct blk_mq_tags *tags;
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busy_tag_iter_fn *fn;
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void *data;
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bool reserved;
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};
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static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
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{
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struct bt_tags_iter_data *iter_data = data;
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struct blk_mq_tags *tags = iter_data->tags;
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bool reserved = iter_data->reserved;
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struct request *rq;
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if (!reserved)
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bitnr += tags->nr_reserved_tags;
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/*
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* We can hit rq == NULL here, because the tagging functions
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* test and set the bit before assining ->rqs[].
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*/
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rq = tags->rqs[bitnr];
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if (rq && blk_mq_request_started(rq))
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return iter_data->fn(rq, iter_data->data, reserved);
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return true;
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}
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/**
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* bt_tags_for_each - iterate over the requests in a tag map
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* @tags: Tag map to iterate over.
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* @bt: sbitmap to examine. This is either the breserved_tags member
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* or the bitmap_tags member of struct blk_mq_tags.
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* @fn: Pointer to the function that will be called for each started
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* request. @fn will be called as follows: @fn(rq, @data,
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* @reserved) where rq is a pointer to a request. Return true
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* to continue iterating tags, false to stop.
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* @data: Will be passed as second argument to @fn.
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* @reserved: Indicates whether @bt is the breserved_tags member or the
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* bitmap_tags member of struct blk_mq_tags.
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*/
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static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
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busy_tag_iter_fn *fn, void *data, bool reserved)
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{
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struct bt_tags_iter_data iter_data = {
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.tags = tags,
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.fn = fn,
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.data = data,
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.reserved = reserved,
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};
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if (tags->rqs)
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sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
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}
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/**
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* blk_mq_all_tag_busy_iter - iterate over all started requests in a tag map
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* @tags: Tag map to iterate over.
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* @fn: Pointer to the function that will be called for each started
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* request. @fn will be called as follows: @fn(rq, @priv,
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* reserved) where rq is a pointer to a request. 'reserved'
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* indicates whether or not @rq is a reserved request. Return
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* true to continue iterating tags, false to stop.
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* @priv: Will be passed as second argument to @fn.
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*/
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static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
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busy_tag_iter_fn *fn, void *priv)
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{
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if (tags->nr_reserved_tags)
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bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
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bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
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}
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/**
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* blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
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* @tagset: Tag set to iterate over.
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* @fn: Pointer to the function that will be called for each started
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* request. @fn will be called as follows: @fn(rq, @priv,
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* reserved) where rq is a pointer to a request. 'reserved'
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* indicates whether or not @rq is a reserved request. Return
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* true to continue iterating tags, false to stop.
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* @priv: Will be passed as second argument to @fn.
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*/
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void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
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busy_tag_iter_fn *fn, void *priv)
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{
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int i;
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for (i = 0; i < tagset->nr_hw_queues; i++) {
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if (tagset->tags && tagset->tags[i])
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blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv);
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}
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}
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EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
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/**
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* blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
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* @q: Request queue to examine.
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* @fn: Pointer to the function that will be called for each request
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* on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
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* reserved) where rq is a pointer to a request and hctx points
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* to the hardware queue associated with the request. 'reserved'
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* indicates whether or not @rq is a reserved request.
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* @priv: Will be passed as third argument to @fn.
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*
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* Note: if @q->tag_set is shared with other request queues then @fn will be
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* called for all requests on all queues that share that tag set and not only
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* for requests associated with @q.
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*/
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void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
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void *priv)
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{
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struct blk_mq_hw_ctx *hctx;
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int i;
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/*
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* __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
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* while the queue is frozen. So we can use q_usage_counter to avoid
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* racing with it. __blk_mq_update_nr_hw_queues() uses
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* synchronize_rcu() to ensure this function left the critical section
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* below.
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*/
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if (!percpu_ref_tryget(&q->q_usage_counter))
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return;
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queue_for_each_hw_ctx(q, hctx, i) {
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struct blk_mq_tags *tags = hctx->tags;
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/*
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* If no software queues are currently mapped to this
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* hardware queue, there's nothing to check
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*/
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if (!blk_mq_hw_queue_mapped(hctx))
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continue;
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if (tags->nr_reserved_tags)
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bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
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bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
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}
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blk_queue_exit(q);
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}
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static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
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bool round_robin, int node)
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{
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return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
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node);
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}
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static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
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int node, int alloc_policy)
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{
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unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
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bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
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if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node))
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goto free_tags;
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if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
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node))
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goto free_bitmap_tags;
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return tags;
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free_bitmap_tags:
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sbitmap_queue_free(&tags->bitmap_tags);
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free_tags:
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kfree(tags);
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return NULL;
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}
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struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
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unsigned int reserved_tags,
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int node, int alloc_policy)
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{
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struct blk_mq_tags *tags;
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if (total_tags > BLK_MQ_TAG_MAX) {
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pr_err("blk-mq: tag depth too large\n");
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return NULL;
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}
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tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
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if (!tags)
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return NULL;
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tags->nr_tags = total_tags;
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tags->nr_reserved_tags = reserved_tags;
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return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
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}
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void blk_mq_free_tags(struct blk_mq_tags *tags)
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{
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sbitmap_queue_free(&tags->bitmap_tags);
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sbitmap_queue_free(&tags->breserved_tags);
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kfree(tags);
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}
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int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
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struct blk_mq_tags **tagsptr, unsigned int tdepth,
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bool can_grow)
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{
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struct blk_mq_tags *tags = *tagsptr;
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if (tdepth <= tags->nr_reserved_tags)
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return -EINVAL;
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/*
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* If we are allowed to grow beyond the original size, allocate
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* a new set of tags before freeing the old one.
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*/
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if (tdepth > tags->nr_tags) {
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struct blk_mq_tag_set *set = hctx->queue->tag_set;
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struct blk_mq_tags *new;
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bool ret;
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if (!can_grow)
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return -EINVAL;
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|
|
/*
|
|
* We need some sort of upper limit, set it high enough that
|
|
* no valid use cases should require more.
|
|
*/
|
|
if (tdepth > 16 * BLKDEV_MAX_RQ)
|
|
return -EINVAL;
|
|
|
|
new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
|
|
tags->nr_reserved_tags);
|
|
if (!new)
|
|
return -ENOMEM;
|
|
ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
|
|
if (ret) {
|
|
blk_mq_free_rq_map(new);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
|
|
blk_mq_free_rq_map(*tagsptr);
|
|
*tagsptr = new;
|
|
} else {
|
|
/*
|
|
* Don't need (or can't) update reserved tags here, they
|
|
* remain static and should never need resizing.
|
|
*/
|
|
sbitmap_queue_resize(&tags->bitmap_tags,
|
|
tdepth - tags->nr_reserved_tags);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* blk_mq_unique_tag() - return a tag that is unique queue-wide
|
|
* @rq: request for which to compute a unique tag
|
|
*
|
|
* The tag field in struct request is unique per hardware queue but not over
|
|
* all hardware queues. Hence this function that returns a tag with the
|
|
* hardware context index in the upper bits and the per hardware queue tag in
|
|
* the lower bits.
|
|
*
|
|
* Note: When called for a request that is queued on a non-multiqueue request
|
|
* queue, the hardware context index is set to zero.
|
|
*/
|
|
u32 blk_mq_unique_tag(struct request *rq)
|
|
{
|
|
return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
|
|
(rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
|
|
}
|
|
EXPORT_SYMBOL(blk_mq_unique_tag);
|