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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Keith Busch](/assets/img/avatar_default.png)
commit530ca2c9bd
upstream. A recent commit runs tag iterator callbacks under the rcu read lock, but existing callbacks do not satisfy the non-blocking requirement. The commit intended to prevent an iterator from accessing a queue that's being modified. This patch fixes the original issue by taking a queue reference instead of reading it, which allows callbacks to make blocking calls. Fixes:f5bbbbe4d6
("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter") Acked-by: Jianchao Wang <jianchao.w.wang@oracle.com> Signed-off-by: Keith Busch <keith.busch@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Giuliano Procida <gprocida@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
496 lines
12 KiB
C
496 lines
12 KiB
C
/*
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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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*/
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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_WAIT(wait);
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unsigned int tag_offset;
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bool drop_ctx;
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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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drop_ctx = data->ctx == NULL;
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do {
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prepare_to_wait(&ws->wait, &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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/*
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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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if (data->ctx)
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blk_mq_put_ctx(data->ctx);
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io_schedule();
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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->ctx->cpu);
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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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finish_wait(&ws->wait, &wait);
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ws = bt_wait_ptr(bt, data->hctx);
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} while (1);
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if (drop_ctx && data->ctx)
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blk_mq_put_ctx(data->ctx);
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finish_wait(&ws->wait, &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 assining ->rqs[].
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*/
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if (rq && rq->q == hctx->queue)
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iter_data->fn(hctx, rq, iter_data->data, reserved);
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return true;
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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)
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iter_data->fn(rq, iter_data->data, reserved);
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return true;
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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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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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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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int blk_mq_reinit_tagset(struct blk_mq_tag_set *set,
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int (reinit_request)(void *, struct request *))
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{
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int i, j, ret = 0;
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if (WARN_ON_ONCE(!reinit_request))
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goto out;
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for (i = 0; i < set->nr_hw_queues; i++) {
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struct blk_mq_tags *tags = set->tags[i];
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if (!tags)
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continue;
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for (j = 0; j < tags->nr_tags; j++) {
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if (!tags->static_rqs[j])
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continue;
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ret = reinit_request(set->driver_data,
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tags->static_rqs[j]);
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if (ret)
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goto out;
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}
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}
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out:
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return ret;
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}
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EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset);
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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 will update the nr_hw_queues and
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* queue_hw_ctx after freeze the queue, so we use q_usage_counter
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* to avoid race with it.
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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 not 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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/*
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* We need some sort of upper limit, set it high enough that
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* no valid use cases should require more.
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*/
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if (tdepth > 16 * BLKDEV_MAX_RQ)
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return -EINVAL;
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new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
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tags->nr_reserved_tags);
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if (!new)
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return -ENOMEM;
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ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
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if (ret) {
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blk_mq_free_rq_map(new);
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return -ENOMEM;
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}
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blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
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blk_mq_free_rq_map(*tagsptr);
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*tagsptr = new;
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} else {
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/*
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* Don't need (or can't) update reserved tags here, they
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* remain static and should never need resizing.
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*/
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sbitmap_queue_resize(&tags->bitmap_tags,
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tdepth - tags->nr_reserved_tags);
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}
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return 0;
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}
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/**
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* blk_mq_unique_tag() - return a tag that is unique queue-wide
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* @rq: request for which to compute a unique tag
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*
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* The tag field in struct request is unique per hardware queue but not over
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* all hardware queues. Hence this function that returns a tag with the
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* hardware context index in the upper bits and the per hardware queue tag in
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* the lower bits.
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*
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* Note: When called for a request that is queued on a non-multiqueue request
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* queue, the hardware context index is set to zero.
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*/
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u32 blk_mq_unique_tag(struct request *rq)
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{
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struct request_queue *q = rq->q;
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struct blk_mq_hw_ctx *hctx;
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int hwq = 0;
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if (q->mq_ops) {
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hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
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hwq = hctx->queue_num;
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}
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return (hwq << BLK_MQ_UNIQUE_TAG_BITS) |
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(rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
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}
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EXPORT_SYMBOL(blk_mq_unique_tag);
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