linux/block/blk-mq-tag.c
Laibin Qiu 180dccb0db blk-mq: fix tag_get wait task can't be awakened
In case of shared tags, there might be more than one hctx which
allocates from the same tags, and each hctx is limited to allocate at
most:
        hctx_max_depth = max((bt->sb.depth + users - 1) / users, 4U);

tag idle detection is lazy, and may be delayed for 30sec, so there
could be just one real active hctx(queue) but all others are actually
idle and still accounted as active because of the lazy idle detection.
Then if wake_batch is > hctx_max_depth, driver tag allocation may wait
forever on this real active hctx.

Fix this by recalculating wake_batch when inc or dec active_queues.

Fixes: 0d2602ca30 ("blk-mq: improve support for shared tags maps")
Suggested-by: Ming Lei <ming.lei@redhat.com>
Suggested-by: John Garry <john.garry@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220113025536.1479653-1-qiulaibin@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-01-13 12:52:14 -07:00

685 lines
18 KiB
C

// 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/blk-mq.h>
#include <linux/delay.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-sched.h"
#include "blk-mq-tag.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.
*/
bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
{
unsigned int users;
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 true;
}
} else {
if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) {
return true;
}
}
users = atomic_inc_return(&hctx->tags->active_queues);
blk_mq_update_wake_batch(hctx->tags, users);
return true;
}
/*
* 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;
}
users = atomic_dec_return(&tags->active_queues);
blk_mq_update_wake_batch(tags, users);
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);
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 {
BUG_ON(tag >= tags->nr_reserved_tags);
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;
bool reserved = iter_data->reserved;
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 (!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, reserved);
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;
bool reserved = iter_data->flags & BT_TAG_ITER_RESERVED;
struct request *rq;
bool ret = true;
bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);
if (!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, reserved);
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, bool reserved)
{
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 queue_hw_ctx
* 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;
int 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);