// SPDX-License-Identifier: GPL-2.0
/*
* Tag allocation using scalable bitmaps. Uses active queue tracking to support
* fairer distribution of tags between multiple submitters when a shared tag map
* is used.
*
* Copyright (C) 2013-2014 Jens Axboe
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-sched.h"
/*
* Recalculate wakeup batch when tag is shared by hctx.
*/
static void blk_mq_update_wake_batch(struct blk_mq_tags *tags,
unsigned int users)
{
if (!users)
return;
sbitmap_queue_recalculate_wake_batch(&tags->bitmap_tags,
users);
sbitmap_queue_recalculate_wake_batch(&tags->breserved_tags,
users);
}
/*
* If a previously inactive queue goes active, bump the active user count.
* We need to do this before try to allocate driver tag, then even if fail
* to get tag when first time, the other shared-tag users could reserve
* budget for it.
*/
void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
{
unsigned int users;
unsigned long flags;
struct blk_mq_tags *tags = hctx->tags;
/*
* calling test_bit() prior to test_and_set_bit() is intentional,
* it avoids dirtying the cacheline if the queue is already active.
*/
if (blk_mq_is_shared_tags(hctx->flags)) {
struct request_queue *q = hctx->queue;
if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
return;
} else {
if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
return;
}
spin_lock_irqsave(&tags->lock, flags);
users = tags->active_queues + 1;
WRITE_ONCE(tags->active_queues, users);
blk_mq_update_wake_batch(tags, users);
spin_unlock_irqrestore(&tags->lock, flags);
}
/*
* Wakeup all potentially sleeping on tags
*/
void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
{
sbitmap_queue_wake_all(&tags->bitmap_tags);
if (include_reserve)
sbitmap_queue_wake_all(&tags->breserved_tags);
}
/*
* If a previously busy queue goes inactive, potential waiters could now
* be allowed to queue. Wake them up and check.
*/
void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
{
struct blk_mq_tags *tags = hctx->tags;
unsigned int users;
if (blk_mq_is_shared_tags(hctx->flags)) {
struct request_queue *q = hctx->queue;
if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
&q->queue_flags))
return;
} else {
if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
return;
}
spin_lock_irq(&tags->lock);
users = tags->active_queues - 1;
WRITE_ONCE(tags->active_queues, users);
blk_mq_update_wake_batch(tags, users);
spin_unlock_irq(&tags->lock);
blk_mq_tag_wakeup_all(tags, false);
}
static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
struct sbitmap_queue *bt)
{
if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
!hctx_may_queue(data->hctx, bt))
return BLK_MQ_NO_TAG;
if (data->shallow_depth)
return sbitmap_queue_get_shallow(bt, data->shallow_depth);
else
return __sbitmap_queue_get(bt);
}
unsigned long blk_mq_get_tags(struct blk_mq_alloc_data *data, int nr_tags,
unsigned int *offset)
{
struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
struct sbitmap_queue *bt = &tags->bitmap_tags;
unsigned long ret;
if (data->shallow_depth ||data->flags & BLK_MQ_REQ_RESERVED ||
data->hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
return 0;
ret = __sbitmap_queue_get_batch(bt, nr_tags, offset);
*offset += tags->nr_reserved_tags;
return ret;
}
unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
{
struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
struct sbitmap_queue *bt;
struct sbq_wait_state *ws;
DEFINE_SBQ_WAIT(wait);
unsigned int tag_offset;
int tag;
if (data->flags & BLK_MQ_REQ_RESERVED) {
if (unlikely(!tags->nr_reserved_tags)) {
WARN_ON_ONCE(1);
return BLK_MQ_NO_TAG;
}
bt = &tags->breserved_tags;
tag_offset = 0;
} else {
bt = &tags->bitmap_tags;
tag_offset = tags->nr_reserved_tags;
}
tag = __blk_mq_get_tag(data, bt);
if (tag != BLK_MQ_NO_TAG)
goto found_tag;
if (data->flags & BLK_MQ_REQ_NOWAIT)
return BLK_MQ_NO_TAG;
ws = bt_wait_ptr(bt, data->hctx);
do {
struct sbitmap_queue *bt_prev;
/*
* We're out of tags on this hardware queue, kick any
* pending IO submits before going to sleep waiting for
* some to complete.
*/
blk_mq_run_hw_queue(data->hctx, false);
/*
* Retry tag allocation after running the hardware queue,
* as running the queue may also have found completions.
*/
tag = __blk_mq_get_tag(data, bt);
if (tag != BLK_MQ_NO_TAG)
break;
sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);
tag = __blk_mq_get_tag(data, bt);
if (tag != BLK_MQ_NO_TAG)
break;
bt_prev = bt;
io_schedule();
sbitmap_finish_wait(bt, ws, &wait);
data->ctx = blk_mq_get_ctx(data->q);
data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
data->ctx);
tags = blk_mq_tags_from_data(data);
if (data->flags & BLK_MQ_REQ_RESERVED)
bt = &tags->breserved_tags;
else
bt = &tags->bitmap_tags;
/*
* If destination hw queue is changed, fake wake up on
* previous queue for compensating the wake up miss, so
* other allocations on previous queue won't be starved.
*/
if (bt != bt_prev)
sbitmap_queue_wake_up(bt_prev, 1);
ws = bt_wait_ptr(bt, data->hctx);
} while (1);
sbitmap_finish_wait(bt, ws, &wait);
found_tag:
/*
* Give up this allocation if the hctx is inactive. The caller will
* retry on an active hctx.
*/
if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
return BLK_MQ_NO_TAG;
}
return tag + tag_offset;
}
void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
unsigned int tag)
{
if (!blk_mq_tag_is_reserved(tags, tag)) {
const int real_tag = tag - tags->nr_reserved_tags;
BUG_ON(real_tag >= tags->nr_tags);
sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu);
} else {
sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu);
}
}
void blk_mq_put_tags(struct blk_mq_tags *tags, int *tag_array, int nr_tags)
{
sbitmap_queue_clear_batch(&tags->bitmap_tags, tags->nr_reserved_tags,
tag_array, nr_tags);
}
struct bt_iter_data {
struct blk_mq_hw_ctx *hctx;
struct request_queue *q;
busy_tag_iter_fn *fn;
void *data;
bool reserved;
};
static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
unsigned int bitnr)
{
struct request *rq;
unsigned long flags;
spin_lock_irqsave(&tags->lock, flags);
rq = tags->rqs[bitnr];
if (!rq || rq->tag != bitnr || !req_ref_inc_not_zero(rq))
rq = NULL;
spin_unlock_irqrestore(&tags->lock, flags);
return rq;
}
static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
{
struct bt_iter_data *iter_data = data;
struct blk_mq_hw_ctx *hctx = iter_data->hctx;
struct request_queue *q = iter_data->q;
struct blk_mq_tag_set *set = q->tag_set;
struct blk_mq_tags *tags;
struct request *rq;
bool ret = true;
if (blk_mq_is_shared_tags(set->flags))
tags = set->shared_tags;
else
tags = hctx->tags;
if (!iter_data->reserved)
bitnr += tags->nr_reserved_tags;
/*
* We can hit rq == NULL here, because the tagging functions
* test and set the bit before assigning ->rqs[].
*/
rq = blk_mq_find_and_get_req(tags, bitnr);
if (!rq)
return true;
if (rq->q == q && (!hctx || rq->mq_hctx == hctx))
ret = iter_data->fn(rq, iter_data->data);
blk_mq_put_rq_ref(rq);
return ret;
}
/**
* bt_for_each - iterate over the requests associated with a hardware queue
* @hctx: Hardware queue to examine.
* @q: Request queue to examine.
* @bt: sbitmap to examine. This is either the breserved_tags member
* or the bitmap_tags member of struct blk_mq_tags.
* @fn: Pointer to the function that will be called for each request
* associated with @hctx that has been assigned a driver tag.
* @fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
* where rq is a pointer to a request. Return true to continue
* iterating tags, false to stop.
* @data: Will be passed as third argument to @fn.
* @reserved: Indicates whether @bt is the breserved_tags member or the
* bitmap_tags member of struct blk_mq_tags.
*/
static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct request_queue *q,
struct sbitmap_queue *bt, busy_tag_iter_fn *fn,
void *data, bool reserved)
{
struct bt_iter_data iter_data = {
.hctx = hctx,
.fn = fn,
.data = data,
.reserved = reserved,
.q = q,
};
sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
}
struct bt_tags_iter_data {
struct blk_mq_tags *tags;
busy_tag_iter_fn *fn;
void *data;
unsigned int flags;
};
#define BT_TAG_ITER_RESERVED (1 << 0)
#define BT_TAG_ITER_STARTED (1 << 1)
#define BT_TAG_ITER_STATIC_RQS (1 << 2)
static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
{
struct bt_tags_iter_data *iter_data = data;
struct blk_mq_tags *tags = iter_data->tags;
struct request *rq;
bool ret = true;
bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);
if (!(iter_data->flags & BT_TAG_ITER_RESERVED))
bitnr += tags->nr_reserved_tags;
/*
* We can hit rq == NULL here, because the tagging functions
* test and set the bit before assigning ->rqs[].
*/
if (iter_static_rqs)
rq = tags->static_rqs[bitnr];
else
rq = blk_mq_find_and_get_req(tags, bitnr);
if (!rq)
return true;
if (!(iter_data->flags & BT_TAG_ITER_STARTED) ||
blk_mq_request_started(rq))
ret = iter_data->fn(rq, iter_data->data);
if (!iter_static_rqs)
blk_mq_put_rq_ref(rq);
return ret;
}
/**
* bt_tags_for_each - iterate over the requests in a tag map
* @tags: Tag map to iterate over.
* @bt: sbitmap to examine. This is either the breserved_tags member
* or the bitmap_tags member of struct blk_mq_tags.
* @fn: Pointer to the function that will be called for each started
* request. @fn will be called as follows: @fn(rq, @data,
* @reserved) where rq is a pointer to a request. Return true
* to continue iterating tags, false to stop.
* @data: Will be passed as second argument to @fn.
* @flags: BT_TAG_ITER_*
*/
static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
busy_tag_iter_fn *fn, void *data, unsigned int flags)
{
struct bt_tags_iter_data iter_data = {
.tags = tags,
.fn = fn,
.data = data,
.flags = flags,
};
if (tags->rqs)
sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
}
static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
busy_tag_iter_fn *fn, void *priv, unsigned int flags)
{
WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
if (tags->nr_reserved_tags)
bt_tags_for_each(tags, &tags->breserved_tags, fn, priv,
flags | BT_TAG_ITER_RESERVED);
bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, flags);
}
/**
* blk_mq_all_tag_iter - iterate over all requests in a tag map
* @tags: Tag map to iterate over.
* @fn: Pointer to the function that will be called for each
* request. @fn will be called as follows: @fn(rq, @priv,
* reserved) where rq is a pointer to a request. 'reserved'
* indicates whether or not @rq is a reserved request. Return
* true to continue iterating tags, false to stop.
* @priv: Will be passed as second argument to @fn.
*
* Caller has to pass the tag map from which requests are allocated.
*/
void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
void *priv)
{
__blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
}
/**
* blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
* @tagset: Tag set to iterate over.
* @fn: Pointer to the function that will be called for each started
* request. @fn will be called as follows: @fn(rq, @priv,
* reserved) where rq is a pointer to a request. 'reserved'
* indicates whether or not @rq is a reserved request. Return
* true to continue iterating tags, false to stop.
* @priv: Will be passed as second argument to @fn.
*
* We grab one request reference before calling @fn and release it after
* @fn returns.
*/
void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
busy_tag_iter_fn *fn, void *priv)
{
unsigned int flags = tagset->flags;
int i, nr_tags;
nr_tags = blk_mq_is_shared_tags(flags) ? 1 : tagset->nr_hw_queues;
for (i = 0; i < nr_tags; i++) {
if (tagset->tags && tagset->tags[i])
__blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
BT_TAG_ITER_STARTED);
}
}
EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
static bool blk_mq_tagset_count_completed_rqs(struct request *rq, void *data)
{
unsigned *count = data;
if (blk_mq_request_completed(rq))
(*count)++;
return true;
}
/**
* blk_mq_tagset_wait_completed_request - Wait until all scheduled request
* completions have finished.
* @tagset: Tag set to drain completed request
*
* Note: This function has to be run after all IO queues are shutdown
*/
void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
{
while (true) {
unsigned count = 0;
blk_mq_tagset_busy_iter(tagset,
blk_mq_tagset_count_completed_rqs, &count);
if (!count)
break;
msleep(5);
}
}
EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);
/**
* blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
* @q: Request queue to examine.
* @fn: Pointer to the function that will be called for each request
* on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
* reserved) where rq is a pointer to a request and hctx points
* to the hardware queue associated with the request. 'reserved'
* indicates whether or not @rq is a reserved request.
* @priv: Will be passed as third argument to @fn.
*
* Note: if @q->tag_set is shared with other request queues then @fn will be
* called for all requests on all queues that share that tag set and not only
* for requests associated with @q.
*/
void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_tag_iter_fn *fn,
void *priv)
{
/*
* __blk_mq_update_nr_hw_queues() updates nr_hw_queues and hctx_table
* while the queue is frozen. So we can use q_usage_counter to avoid
* racing with it.
*/
if (!percpu_ref_tryget(&q->q_usage_counter))
return;
if (blk_mq_is_shared_tags(q->tag_set->flags)) {
struct blk_mq_tags *tags = q->tag_set->shared_tags;
struct sbitmap_queue *bresv = &tags->breserved_tags;
struct sbitmap_queue *btags = &tags->bitmap_tags;
if (tags->nr_reserved_tags)
bt_for_each(NULL, q, bresv, fn, priv, true);
bt_for_each(NULL, q, btags, fn, priv, false);
} else {
struct blk_mq_hw_ctx *hctx;
unsigned long i;
queue_for_each_hw_ctx(q, hctx, i) {
struct blk_mq_tags *tags = hctx->tags;
struct sbitmap_queue *bresv = &tags->breserved_tags;
struct sbitmap_queue *btags = &tags->bitmap_tags;
/*
* If no software queues are currently mapped to this
* hardware queue, there's nothing to check
*/
if (!blk_mq_hw_queue_mapped(hctx))
continue;
if (tags->nr_reserved_tags)
bt_for_each(hctx, q, bresv, fn, priv, true);
bt_for_each(hctx, q, btags, fn, priv, false);
}
}
blk_queue_exit(q);
}
static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
bool round_robin, int node)
{
return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
node);
}
int blk_mq_init_bitmaps(struct sbitmap_queue *bitmap_tags,
struct sbitmap_queue *breserved_tags,
unsigned int queue_depth, unsigned int reserved,
int node, int alloc_policy)
{
unsigned int depth = queue_depth - reserved;
bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
if (bt_alloc(bitmap_tags, depth, round_robin, node))
return -ENOMEM;
if (bt_alloc(breserved_tags, reserved, round_robin, node))
goto free_bitmap_tags;
return 0;
free_bitmap_tags:
sbitmap_queue_free(bitmap_tags);
return -ENOMEM;
}
struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
unsigned int reserved_tags,
int node, int alloc_policy)
{
struct blk_mq_tags *tags;
if (total_tags > BLK_MQ_TAG_MAX) {
pr_err("blk-mq: tag depth too large\n");
return NULL;
}
tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
if (!tags)
return NULL;
tags->nr_tags = total_tags;
tags->nr_reserved_tags = reserved_tags;
spin_lock_init(&tags->lock);
if (blk_mq_init_bitmaps(&tags->bitmap_tags, &tags->breserved_tags,
total_tags, reserved_tags, node,
alloc_policy) < 0) {
kfree(tags);
return NULL;
}
return tags;
}
void blk_mq_free_tags(struct blk_mq_tags *tags)
{
sbitmap_queue_free(&tags->bitmap_tags);
sbitmap_queue_free(&tags->breserved_tags);
kfree(tags);
}
int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
struct blk_mq_tags **tagsptr, unsigned int tdepth,
bool can_grow)
{
struct blk_mq_tags *tags = *tagsptr;
if (tdepth <= tags->nr_reserved_tags)
return -EINVAL;
/*
* If we are allowed to grow beyond the original size, allocate
* a new set of tags before freeing the old one.
*/
if (tdepth > tags->nr_tags) {
struct blk_mq_tag_set *set = hctx->queue->tag_set;
struct blk_mq_tags *new;
if (!can_grow)
return -EINVAL;
/*
* We need some sort of upper limit, set it high enough that
* no valid use cases should require more.
*/
if (tdepth > MAX_SCHED_RQ)
return -EINVAL;
/*
* Only the sbitmap needs resizing since we allocated the max
* initially.
*/
if (blk_mq_is_shared_tags(set->flags))
return 0;
new = blk_mq_alloc_map_and_rqs(set, hctx->queue_num, tdepth);
if (!new)
return -ENOMEM;
blk_mq_free_map_and_rqs(set, *tagsptr, hctx->queue_num);
*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;
}
void blk_mq_tag_resize_shared_tags(struct blk_mq_tag_set *set, unsigned int size)
{
struct blk_mq_tags *tags = set->shared_tags;
sbitmap_queue_resize(&tags->bitmap_tags, size - set->reserved_tags);
}
void blk_mq_tag_update_sched_shared_tags(struct request_queue *q)
{
sbitmap_queue_resize(&q->sched_shared_tags->bitmap_tags,
q->nr_requests - q->tag_set->reserved_tags);
}
/**
* 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);
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