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![Christoph Hellwig](/assets/img/avatar_default.png)
A lot of the REQ_* flags are only used on struct requests, and only of use to the block layer and a few drivers that dig into struct request internals. This patch adds a new req_flags_t rq_flags field to struct request for them, and thus dramatically shrinks the number of common requests. It also removes the unfortunate situation where we have to fit the fields from the same enum into 32 bits for struct bio and 64 bits for struct request. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Shaun Tancheff <shaun.tancheff@seagate.com> Signed-off-by: Jens Axboe <axboe@fb.com>
402 lines
10 KiB
C
402 lines
10 KiB
C
/*
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* Functions related to tagged command queuing
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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/bio.h>
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#include <linux/blkdev.h>
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#include <linux/slab.h>
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#include "blk.h"
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/**
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* blk_queue_find_tag - find a request by its tag and queue
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* @q: The request queue for the device
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* @tag: The tag of the request
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*
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* Notes:
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* Should be used when a device returns a tag and you want to match
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* it with a request.
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*
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* no locks need be held.
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**/
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struct request *blk_queue_find_tag(struct request_queue *q, int tag)
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{
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return blk_map_queue_find_tag(q->queue_tags, tag);
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}
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EXPORT_SYMBOL(blk_queue_find_tag);
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/**
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* blk_free_tags - release a given set of tag maintenance info
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* @bqt: the tag map to free
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*
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* Drop the reference count on @bqt and frees it when the last reference
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* is dropped.
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*/
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void blk_free_tags(struct blk_queue_tag *bqt)
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{
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if (atomic_dec_and_test(&bqt->refcnt)) {
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BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
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bqt->max_depth);
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kfree(bqt->tag_index);
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bqt->tag_index = NULL;
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kfree(bqt->tag_map);
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bqt->tag_map = NULL;
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kfree(bqt);
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}
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}
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EXPORT_SYMBOL(blk_free_tags);
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/**
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* __blk_queue_free_tags - release tag maintenance info
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* @q: the request queue for the device
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*
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* Notes:
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* blk_cleanup_queue() will take care of calling this function, if tagging
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* has been used. So there's no need to call this directly.
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**/
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void __blk_queue_free_tags(struct request_queue *q)
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{
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struct blk_queue_tag *bqt = q->queue_tags;
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if (!bqt)
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return;
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blk_free_tags(bqt);
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q->queue_tags = NULL;
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queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
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}
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/**
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* blk_queue_free_tags - release tag maintenance info
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* @q: the request queue for the device
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*
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* Notes:
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* This is used to disable tagged queuing to a device, yet leave
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* queue in function.
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**/
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void blk_queue_free_tags(struct request_queue *q)
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{
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queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
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}
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EXPORT_SYMBOL(blk_queue_free_tags);
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static int
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init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
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{
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struct request **tag_index;
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unsigned long *tag_map;
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int nr_ulongs;
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if (q && depth > q->nr_requests * 2) {
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depth = q->nr_requests * 2;
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printk(KERN_ERR "%s: adjusted depth to %d\n",
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__func__, depth);
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}
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tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
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if (!tag_index)
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goto fail;
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nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
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tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
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if (!tag_map)
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goto fail;
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tags->real_max_depth = depth;
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tags->max_depth = depth;
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tags->tag_index = tag_index;
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tags->tag_map = tag_map;
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return 0;
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fail:
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kfree(tag_index);
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return -ENOMEM;
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}
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static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
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int depth, int alloc_policy)
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{
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struct blk_queue_tag *tags;
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tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
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if (!tags)
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goto fail;
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if (init_tag_map(q, tags, depth))
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goto fail;
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atomic_set(&tags->refcnt, 1);
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tags->alloc_policy = alloc_policy;
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tags->next_tag = 0;
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return tags;
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fail:
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kfree(tags);
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return NULL;
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}
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/**
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* blk_init_tags - initialize the tag info for an external tag map
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* @depth: the maximum queue depth supported
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* @alloc_policy: tag allocation policy
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**/
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struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy)
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{
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return __blk_queue_init_tags(NULL, depth, alloc_policy);
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}
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EXPORT_SYMBOL(blk_init_tags);
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/**
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* blk_queue_init_tags - initialize the queue tag info
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* @q: the request queue for the device
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* @depth: the maximum queue depth supported
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* @tags: the tag to use
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* @alloc_policy: tag allocation policy
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*
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* Queue lock must be held here if the function is called to resize an
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* existing map.
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**/
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int blk_queue_init_tags(struct request_queue *q, int depth,
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struct blk_queue_tag *tags, int alloc_policy)
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{
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int rc;
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BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
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if (!tags && !q->queue_tags) {
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tags = __blk_queue_init_tags(q, depth, alloc_policy);
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if (!tags)
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return -ENOMEM;
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} else if (q->queue_tags) {
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rc = blk_queue_resize_tags(q, depth);
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if (rc)
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return rc;
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queue_flag_set(QUEUE_FLAG_QUEUED, q);
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return 0;
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} else
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atomic_inc(&tags->refcnt);
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/*
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* assign it, all done
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*/
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q->queue_tags = tags;
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queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
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INIT_LIST_HEAD(&q->tag_busy_list);
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return 0;
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}
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EXPORT_SYMBOL(blk_queue_init_tags);
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/**
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* blk_queue_resize_tags - change the queueing depth
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* @q: the request queue for the device
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* @new_depth: the new max command queueing depth
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*
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* Notes:
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* Must be called with the queue lock held.
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**/
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int blk_queue_resize_tags(struct request_queue *q, int new_depth)
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{
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struct blk_queue_tag *bqt = q->queue_tags;
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struct request **tag_index;
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unsigned long *tag_map;
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int max_depth, nr_ulongs;
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if (!bqt)
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return -ENXIO;
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/*
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* if we already have large enough real_max_depth. just
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* adjust max_depth. *NOTE* as requests with tag value
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* between new_depth and real_max_depth can be in-flight, tag
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* map can not be shrunk blindly here.
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*/
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if (new_depth <= bqt->real_max_depth) {
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bqt->max_depth = new_depth;
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return 0;
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}
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/*
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* Currently cannot replace a shared tag map with a new
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* one, so error out if this is the case
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*/
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if (atomic_read(&bqt->refcnt) != 1)
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return -EBUSY;
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/*
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* save the old state info, so we can copy it back
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*/
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tag_index = bqt->tag_index;
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tag_map = bqt->tag_map;
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max_depth = bqt->real_max_depth;
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if (init_tag_map(q, bqt, new_depth))
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return -ENOMEM;
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memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
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nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
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memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
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kfree(tag_index);
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kfree(tag_map);
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return 0;
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}
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EXPORT_SYMBOL(blk_queue_resize_tags);
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/**
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* blk_queue_end_tag - end tag operations for a request
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* @q: the request queue for the device
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* @rq: the request that has completed
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*
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* Description:
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* Typically called when end_that_request_first() returns %0, meaning
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* all transfers have been done for a request. It's important to call
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* this function before end_that_request_last(), as that will put the
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* request back on the free list thus corrupting the internal tag list.
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*
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* Notes:
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* queue lock must be held.
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**/
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void blk_queue_end_tag(struct request_queue *q, struct request *rq)
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{
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struct blk_queue_tag *bqt = q->queue_tags;
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unsigned tag = rq->tag; /* negative tags invalid */
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BUG_ON(tag >= bqt->real_max_depth);
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list_del_init(&rq->queuelist);
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rq->rq_flags &= ~RQF_QUEUED;
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rq->tag = -1;
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if (unlikely(bqt->tag_index[tag] == NULL))
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printk(KERN_ERR "%s: tag %d is missing\n",
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__func__, tag);
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bqt->tag_index[tag] = NULL;
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if (unlikely(!test_bit(tag, bqt->tag_map))) {
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printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
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__func__, tag);
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return;
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}
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/*
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* The tag_map bit acts as a lock for tag_index[bit], so we need
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* unlock memory barrier semantics.
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*/
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clear_bit_unlock(tag, bqt->tag_map);
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}
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EXPORT_SYMBOL(blk_queue_end_tag);
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/**
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* blk_queue_start_tag - find a free tag and assign it
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* @q: the request queue for the device
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* @rq: the block request that needs tagging
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*
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* Description:
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* This can either be used as a stand-alone helper, or possibly be
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* assigned as the queue &prep_rq_fn (in which case &struct request
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* automagically gets a tag assigned). Note that this function
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* assumes that any type of request can be queued! if this is not
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* true for your device, you must check the request type before
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* calling this function. The request will also be removed from
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* the request queue, so it's the drivers responsibility to readd
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* it if it should need to be restarted for some reason.
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*
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* Notes:
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* queue lock must be held.
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**/
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int blk_queue_start_tag(struct request_queue *q, struct request *rq)
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{
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struct blk_queue_tag *bqt = q->queue_tags;
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unsigned max_depth;
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int tag;
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if (unlikely((rq->rq_flags & RQF_QUEUED))) {
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printk(KERN_ERR
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"%s: request %p for device [%s] already tagged %d",
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__func__, rq,
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rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
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BUG();
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}
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/*
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* Protect against shared tag maps, as we may not have exclusive
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* access to the tag map.
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*
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* We reserve a few tags just for sync IO, since we don't want
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* to starve sync IO on behalf of flooding async IO.
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*/
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max_depth = bqt->max_depth;
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if (!rq_is_sync(rq) && max_depth > 1) {
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switch (max_depth) {
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case 2:
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max_depth = 1;
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break;
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case 3:
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max_depth = 2;
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break;
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default:
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max_depth -= 2;
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}
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if (q->in_flight[BLK_RW_ASYNC] > max_depth)
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return 1;
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}
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do {
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if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) {
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tag = find_first_zero_bit(bqt->tag_map, max_depth);
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if (tag >= max_depth)
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return 1;
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} else {
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int start = bqt->next_tag;
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int size = min_t(int, bqt->max_depth, max_depth + start);
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tag = find_next_zero_bit(bqt->tag_map, size, start);
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if (tag >= size && start + size > bqt->max_depth) {
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size = start + size - bqt->max_depth;
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tag = find_first_zero_bit(bqt->tag_map, size);
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}
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if (tag >= size)
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return 1;
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}
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} while (test_and_set_bit_lock(tag, bqt->tag_map));
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/*
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* We need lock ordering semantics given by test_and_set_bit_lock.
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* See blk_queue_end_tag for details.
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*/
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bqt->next_tag = (tag + 1) % bqt->max_depth;
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rq->rq_flags |= RQF_QUEUED;
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rq->tag = tag;
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bqt->tag_index[tag] = rq;
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blk_start_request(rq);
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list_add(&rq->queuelist, &q->tag_busy_list);
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return 0;
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}
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EXPORT_SYMBOL(blk_queue_start_tag);
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/**
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* blk_queue_invalidate_tags - invalidate all pending tags
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* @q: the request queue for the device
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*
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* Description:
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* Hardware conditions may dictate a need to stop all pending requests.
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* In this case, we will safely clear the block side of the tag queue and
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* readd all requests to the request queue in the right order.
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*
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* Notes:
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* queue lock must be held.
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**/
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void blk_queue_invalidate_tags(struct request_queue *q)
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{
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struct list_head *tmp, *n;
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list_for_each_safe(tmp, n, &q->tag_busy_list)
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blk_requeue_request(q, list_entry_rq(tmp));
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}
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EXPORT_SYMBOL(blk_queue_invalidate_tags);
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