![Jens Axboe](/assets/img/avatar_default.png)
Linux currently has two models for block devices: - The classic request_fn based approach, where drivers use struct request units for IO. The block layer provides various helper functionalities to let drivers share code, things like tag management, timeout handling, queueing, etc. - The "stacked" approach, where a driver squeezes in between the block layer and IO submitter. Since this bypasses the IO stack, driver generally have to manage everything themselves. With drivers being written for new high IOPS devices, the classic request_fn based driver doesn't work well enough. The design dates back to when both SMP and high IOPS was rare. It has problems with scaling to bigger machines, and runs into scaling issues even on smaller machines when you have IOPS in the hundreds of thousands per device. The stacked approach is then most often selected as the model for the driver. But this means that everybody has to re-invent everything, and along with that we get all the problems again that the shared approach solved. This commit introduces blk-mq, block multi queue support. The design is centered around per-cpu queues for queueing IO, which then funnel down into x number of hardware submission queues. We might have a 1:1 mapping between the two, or it might be an N:M mapping. That all depends on what the hardware supports. blk-mq provides various helper functions, which include: - Scalable support for request tagging. Most devices need to be able to uniquely identify a request both in the driver and to the hardware. The tagging uses per-cpu caches for freed tags, to enable cache hot reuse. - Timeout handling without tracking request on a per-device basis. Basically the driver should be able to get a notification, if a request happens to fail. - Optional support for non 1:1 mappings between issue and submission queues. blk-mq can redirect IO completions to the desired location. - Support for per-request payloads. Drivers almost always need to associate a request structure with some driver private command structure. Drivers can tell blk-mq this at init time, and then any request handed to the driver will have the required size of memory associated with it. - Support for merging of IO, and plugging. The stacked model gets neither of these. Even for high IOPS devices, merging sequential IO reduces per-command overhead and thus increases bandwidth. For now, this is provided as a potential 3rd queueing model, with the hope being that, as it matures, it can replace both the classic and stacked model. That would get us back to having just 1 real model for block devices, leaving the stacked approach to dm/md devices (as it was originally intended). Contributions in this patch from the following people: Shaohua Li <shli@fusionio.com> Alexander Gordeev <agordeev@redhat.com> Christoph Hellwig <hch@infradead.org> Mike Christie <michaelc@cs.wisc.edu> Matias Bjorling <m@bjorling.me> Jeff Moyer <jmoyer@redhat.com> Acked-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
634 lines
16 KiB
C
634 lines
16 KiB
C
/*
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* Functions related to sysfs handling
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*/
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#include <linux/kernel.h>
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#include <linux/slab.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/blktrace_api.h>
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#include <linux/blk-mq.h>
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#include "blk.h"
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#include "blk-cgroup.h"
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struct queue_sysfs_entry {
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struct attribute attr;
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ssize_t (*show)(struct request_queue *, char *);
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ssize_t (*store)(struct request_queue *, const char *, size_t);
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};
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static ssize_t
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queue_var_show(unsigned long var, char *page)
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{
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return sprintf(page, "%lu\n", var);
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}
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static ssize_t
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queue_var_store(unsigned long *var, const char *page, size_t count)
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{
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int err;
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unsigned long v;
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err = kstrtoul(page, 10, &v);
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if (err || v > UINT_MAX)
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return -EINVAL;
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*var = v;
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return count;
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}
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static ssize_t queue_requests_show(struct request_queue *q, char *page)
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{
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return queue_var_show(q->nr_requests, (page));
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}
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static ssize_t
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queue_requests_store(struct request_queue *q, const char *page, size_t count)
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{
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struct request_list *rl;
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unsigned long nr;
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int ret;
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if (!q->request_fn)
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return -EINVAL;
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ret = queue_var_store(&nr, page, count);
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if (ret < 0)
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return ret;
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if (nr < BLKDEV_MIN_RQ)
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nr = BLKDEV_MIN_RQ;
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spin_lock_irq(q->queue_lock);
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q->nr_requests = nr;
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blk_queue_congestion_threshold(q);
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/* congestion isn't cgroup aware and follows root blkcg for now */
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rl = &q->root_rl;
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if (rl->count[BLK_RW_SYNC] >= queue_congestion_on_threshold(q))
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blk_set_queue_congested(q, BLK_RW_SYNC);
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else if (rl->count[BLK_RW_SYNC] < queue_congestion_off_threshold(q))
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blk_clear_queue_congested(q, BLK_RW_SYNC);
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if (rl->count[BLK_RW_ASYNC] >= queue_congestion_on_threshold(q))
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blk_set_queue_congested(q, BLK_RW_ASYNC);
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else if (rl->count[BLK_RW_ASYNC] < queue_congestion_off_threshold(q))
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blk_clear_queue_congested(q, BLK_RW_ASYNC);
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blk_queue_for_each_rl(rl, q) {
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if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
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blk_set_rl_full(rl, BLK_RW_SYNC);
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} else {
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blk_clear_rl_full(rl, BLK_RW_SYNC);
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wake_up(&rl->wait[BLK_RW_SYNC]);
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}
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if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
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blk_set_rl_full(rl, BLK_RW_ASYNC);
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} else {
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blk_clear_rl_full(rl, BLK_RW_ASYNC);
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wake_up(&rl->wait[BLK_RW_ASYNC]);
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}
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}
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spin_unlock_irq(q->queue_lock);
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return ret;
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}
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static ssize_t queue_ra_show(struct request_queue *q, char *page)
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{
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unsigned long ra_kb = q->backing_dev_info.ra_pages <<
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(PAGE_CACHE_SHIFT - 10);
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return queue_var_show(ra_kb, (page));
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}
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static ssize_t
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queue_ra_store(struct request_queue *q, const char *page, size_t count)
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{
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unsigned long ra_kb;
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ssize_t ret = queue_var_store(&ra_kb, page, count);
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if (ret < 0)
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return ret;
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q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
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return ret;
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}
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static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
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{
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int max_sectors_kb = queue_max_sectors(q) >> 1;
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return queue_var_show(max_sectors_kb, (page));
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}
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static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_max_segments(q), (page));
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}
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static ssize_t queue_max_integrity_segments_show(struct request_queue *q, char *page)
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{
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return queue_var_show(q->limits.max_integrity_segments, (page));
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}
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static ssize_t queue_max_segment_size_show(struct request_queue *q, char *page)
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{
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if (blk_queue_cluster(q))
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return queue_var_show(queue_max_segment_size(q), (page));
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return queue_var_show(PAGE_CACHE_SIZE, (page));
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}
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static ssize_t queue_logical_block_size_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_logical_block_size(q), page);
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}
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static ssize_t queue_physical_block_size_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_physical_block_size(q), page);
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}
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static ssize_t queue_io_min_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_io_min(q), page);
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}
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static ssize_t queue_io_opt_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_io_opt(q), page);
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}
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static ssize_t queue_discard_granularity_show(struct request_queue *q, char *page)
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{
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return queue_var_show(q->limits.discard_granularity, page);
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}
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static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
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{
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return sprintf(page, "%llu\n",
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(unsigned long long)q->limits.max_discard_sectors << 9);
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}
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static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *page)
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{
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return queue_var_show(queue_discard_zeroes_data(q), page);
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}
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static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
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{
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return sprintf(page, "%llu\n",
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(unsigned long long)q->limits.max_write_same_sectors << 9);
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}
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static ssize_t
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queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
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{
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unsigned long max_sectors_kb,
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max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
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page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
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ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
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if (ret < 0)
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return ret;
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if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
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return -EINVAL;
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spin_lock_irq(q->queue_lock);
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q->limits.max_sectors = max_sectors_kb << 1;
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spin_unlock_irq(q->queue_lock);
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return ret;
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}
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static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
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{
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int max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1;
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return queue_var_show(max_hw_sectors_kb, (page));
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}
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#define QUEUE_SYSFS_BIT_FNS(name, flag, neg) \
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static ssize_t \
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queue_show_##name(struct request_queue *q, char *page) \
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{ \
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int bit; \
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bit = test_bit(QUEUE_FLAG_##flag, &q->queue_flags); \
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return queue_var_show(neg ? !bit : bit, page); \
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} \
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static ssize_t \
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queue_store_##name(struct request_queue *q, const char *page, size_t count) \
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{ \
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unsigned long val; \
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ssize_t ret; \
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ret = queue_var_store(&val, page, count); \
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if (ret < 0) \
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return ret; \
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if (neg) \
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val = !val; \
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\
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spin_lock_irq(q->queue_lock); \
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if (val) \
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queue_flag_set(QUEUE_FLAG_##flag, q); \
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else \
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queue_flag_clear(QUEUE_FLAG_##flag, q); \
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spin_unlock_irq(q->queue_lock); \
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return ret; \
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}
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QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
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QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
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QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
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#undef QUEUE_SYSFS_BIT_FNS
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static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
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{
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return queue_var_show((blk_queue_nomerges(q) << 1) |
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blk_queue_noxmerges(q), page);
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}
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static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
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size_t count)
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{
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unsigned long nm;
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ssize_t ret = queue_var_store(&nm, page, count);
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if (ret < 0)
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return ret;
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spin_lock_irq(q->queue_lock);
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queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
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queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
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if (nm == 2)
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queue_flag_set(QUEUE_FLAG_NOMERGES, q);
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else if (nm)
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queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
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spin_unlock_irq(q->queue_lock);
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return ret;
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}
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static ssize_t queue_rq_affinity_show(struct request_queue *q, char *page)
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{
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bool set = test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags);
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bool force = test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags);
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return queue_var_show(set << force, page);
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}
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static ssize_t
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queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
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{
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ssize_t ret = -EINVAL;
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#if defined(CONFIG_USE_GENERIC_SMP_HELPERS)
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unsigned long val;
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ret = queue_var_store(&val, page, count);
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if (ret < 0)
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return ret;
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spin_lock_irq(q->queue_lock);
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if (val == 2) {
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queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
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queue_flag_set(QUEUE_FLAG_SAME_FORCE, q);
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} else if (val == 1) {
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queue_flag_set(QUEUE_FLAG_SAME_COMP, q);
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queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
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} else if (val == 0) {
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queue_flag_clear(QUEUE_FLAG_SAME_COMP, q);
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queue_flag_clear(QUEUE_FLAG_SAME_FORCE, q);
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}
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spin_unlock_irq(q->queue_lock);
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#endif
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return ret;
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}
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static struct queue_sysfs_entry queue_requests_entry = {
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.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
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.show = queue_requests_show,
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.store = queue_requests_store,
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};
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static struct queue_sysfs_entry queue_ra_entry = {
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.attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
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.show = queue_ra_show,
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.store = queue_ra_store,
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};
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static struct queue_sysfs_entry queue_max_sectors_entry = {
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.attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
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.show = queue_max_sectors_show,
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.store = queue_max_sectors_store,
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};
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static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
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.attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
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.show = queue_max_hw_sectors_show,
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};
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static struct queue_sysfs_entry queue_max_segments_entry = {
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.attr = {.name = "max_segments", .mode = S_IRUGO },
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.show = queue_max_segments_show,
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};
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static struct queue_sysfs_entry queue_max_integrity_segments_entry = {
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.attr = {.name = "max_integrity_segments", .mode = S_IRUGO },
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.show = queue_max_integrity_segments_show,
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};
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static struct queue_sysfs_entry queue_max_segment_size_entry = {
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.attr = {.name = "max_segment_size", .mode = S_IRUGO },
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.show = queue_max_segment_size_show,
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};
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static struct queue_sysfs_entry queue_iosched_entry = {
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.attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
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.show = elv_iosched_show,
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.store = elv_iosched_store,
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};
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static struct queue_sysfs_entry queue_hw_sector_size_entry = {
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.attr = {.name = "hw_sector_size", .mode = S_IRUGO },
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.show = queue_logical_block_size_show,
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};
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static struct queue_sysfs_entry queue_logical_block_size_entry = {
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.attr = {.name = "logical_block_size", .mode = S_IRUGO },
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.show = queue_logical_block_size_show,
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};
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static struct queue_sysfs_entry queue_physical_block_size_entry = {
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.attr = {.name = "physical_block_size", .mode = S_IRUGO },
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.show = queue_physical_block_size_show,
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};
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static struct queue_sysfs_entry queue_io_min_entry = {
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.attr = {.name = "minimum_io_size", .mode = S_IRUGO },
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.show = queue_io_min_show,
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};
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static struct queue_sysfs_entry queue_io_opt_entry = {
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.attr = {.name = "optimal_io_size", .mode = S_IRUGO },
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.show = queue_io_opt_show,
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};
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static struct queue_sysfs_entry queue_discard_granularity_entry = {
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.attr = {.name = "discard_granularity", .mode = S_IRUGO },
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.show = queue_discard_granularity_show,
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};
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static struct queue_sysfs_entry queue_discard_max_entry = {
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.attr = {.name = "discard_max_bytes", .mode = S_IRUGO },
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.show = queue_discard_max_show,
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};
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static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
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.attr = {.name = "discard_zeroes_data", .mode = S_IRUGO },
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.show = queue_discard_zeroes_data_show,
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};
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static struct queue_sysfs_entry queue_write_same_max_entry = {
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.attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
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.show = queue_write_same_max_show,
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};
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static struct queue_sysfs_entry queue_nonrot_entry = {
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.attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
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.show = queue_show_nonrot,
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.store = queue_store_nonrot,
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};
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static struct queue_sysfs_entry queue_nomerges_entry = {
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.attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
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.show = queue_nomerges_show,
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.store = queue_nomerges_store,
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};
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static struct queue_sysfs_entry queue_rq_affinity_entry = {
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.attr = {.name = "rq_affinity", .mode = S_IRUGO | S_IWUSR },
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.show = queue_rq_affinity_show,
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.store = queue_rq_affinity_store,
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};
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static struct queue_sysfs_entry queue_iostats_entry = {
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.attr = {.name = "iostats", .mode = S_IRUGO | S_IWUSR },
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.show = queue_show_iostats,
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.store = queue_store_iostats,
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};
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static struct queue_sysfs_entry queue_random_entry = {
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.attr = {.name = "add_random", .mode = S_IRUGO | S_IWUSR },
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.show = queue_show_random,
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.store = queue_store_random,
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};
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static struct attribute *default_attrs[] = {
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&queue_requests_entry.attr,
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&queue_ra_entry.attr,
|
|
&queue_max_hw_sectors_entry.attr,
|
|
&queue_max_sectors_entry.attr,
|
|
&queue_max_segments_entry.attr,
|
|
&queue_max_integrity_segments_entry.attr,
|
|
&queue_max_segment_size_entry.attr,
|
|
&queue_iosched_entry.attr,
|
|
&queue_hw_sector_size_entry.attr,
|
|
&queue_logical_block_size_entry.attr,
|
|
&queue_physical_block_size_entry.attr,
|
|
&queue_io_min_entry.attr,
|
|
&queue_io_opt_entry.attr,
|
|
&queue_discard_granularity_entry.attr,
|
|
&queue_discard_max_entry.attr,
|
|
&queue_discard_zeroes_data_entry.attr,
|
|
&queue_write_same_max_entry.attr,
|
|
&queue_nonrot_entry.attr,
|
|
&queue_nomerges_entry.attr,
|
|
&queue_rq_affinity_entry.attr,
|
|
&queue_iostats_entry.attr,
|
|
&queue_random_entry.attr,
|
|
NULL,
|
|
};
|
|
|
|
#define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
|
|
|
|
static ssize_t
|
|
queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
|
|
{
|
|
struct queue_sysfs_entry *entry = to_queue(attr);
|
|
struct request_queue *q =
|
|
container_of(kobj, struct request_queue, kobj);
|
|
ssize_t res;
|
|
|
|
if (!entry->show)
|
|
return -EIO;
|
|
mutex_lock(&q->sysfs_lock);
|
|
if (blk_queue_dying(q)) {
|
|
mutex_unlock(&q->sysfs_lock);
|
|
return -ENOENT;
|
|
}
|
|
res = entry->show(q, page);
|
|
mutex_unlock(&q->sysfs_lock);
|
|
return res;
|
|
}
|
|
|
|
static ssize_t
|
|
queue_attr_store(struct kobject *kobj, struct attribute *attr,
|
|
const char *page, size_t length)
|
|
{
|
|
struct queue_sysfs_entry *entry = to_queue(attr);
|
|
struct request_queue *q;
|
|
ssize_t res;
|
|
|
|
if (!entry->store)
|
|
return -EIO;
|
|
|
|
q = container_of(kobj, struct request_queue, kobj);
|
|
mutex_lock(&q->sysfs_lock);
|
|
if (blk_queue_dying(q)) {
|
|
mutex_unlock(&q->sysfs_lock);
|
|
return -ENOENT;
|
|
}
|
|
res = entry->store(q, page, length);
|
|
mutex_unlock(&q->sysfs_lock);
|
|
return res;
|
|
}
|
|
|
|
static void blk_free_queue_rcu(struct rcu_head *rcu_head)
|
|
{
|
|
struct request_queue *q = container_of(rcu_head, struct request_queue,
|
|
rcu_head);
|
|
kmem_cache_free(blk_requestq_cachep, q);
|
|
}
|
|
|
|
/**
|
|
* blk_release_queue: - release a &struct request_queue when it is no longer needed
|
|
* @kobj: the kobj belonging to the request queue to be released
|
|
*
|
|
* Description:
|
|
* blk_release_queue is the pair to blk_init_queue() or
|
|
* blk_queue_make_request(). It should be called when a request queue is
|
|
* being released; typically when a block device is being de-registered.
|
|
* Currently, its primary task it to free all the &struct request
|
|
* structures that were allocated to the queue and the queue itself.
|
|
*
|
|
* Caveat:
|
|
* Hopefully the low level driver will have finished any
|
|
* outstanding requests first...
|
|
**/
|
|
static void blk_release_queue(struct kobject *kobj)
|
|
{
|
|
struct request_queue *q =
|
|
container_of(kobj, struct request_queue, kobj);
|
|
|
|
blk_sync_queue(q);
|
|
|
|
blkcg_exit_queue(q);
|
|
|
|
if (q->elevator) {
|
|
spin_lock_irq(q->queue_lock);
|
|
ioc_clear_queue(q);
|
|
spin_unlock_irq(q->queue_lock);
|
|
elevator_exit(q->elevator);
|
|
}
|
|
|
|
blk_exit_rl(&q->root_rl);
|
|
|
|
if (q->queue_tags)
|
|
__blk_queue_free_tags(q);
|
|
|
|
percpu_counter_destroy(&q->mq_usage_counter);
|
|
|
|
if (q->mq_ops)
|
|
blk_mq_free_queue(q);
|
|
|
|
blk_trace_shutdown(q);
|
|
|
|
bdi_destroy(&q->backing_dev_info);
|
|
|
|
ida_simple_remove(&blk_queue_ida, q->id);
|
|
call_rcu(&q->rcu_head, blk_free_queue_rcu);
|
|
}
|
|
|
|
static const struct sysfs_ops queue_sysfs_ops = {
|
|
.show = queue_attr_show,
|
|
.store = queue_attr_store,
|
|
};
|
|
|
|
struct kobj_type blk_queue_ktype = {
|
|
.sysfs_ops = &queue_sysfs_ops,
|
|
.default_attrs = default_attrs,
|
|
.release = blk_release_queue,
|
|
};
|
|
|
|
int blk_register_queue(struct gendisk *disk)
|
|
{
|
|
int ret;
|
|
struct device *dev = disk_to_dev(disk);
|
|
struct request_queue *q = disk->queue;
|
|
|
|
if (WARN_ON(!q))
|
|
return -ENXIO;
|
|
|
|
/*
|
|
* Initialization must be complete by now. Finish the initial
|
|
* bypass from queue allocation.
|
|
*/
|
|
blk_queue_bypass_end(q);
|
|
queue_flag_set_unlocked(QUEUE_FLAG_INIT_DONE, q);
|
|
|
|
ret = blk_trace_init_sysfs(dev);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
|
|
if (ret < 0) {
|
|
blk_trace_remove_sysfs(dev);
|
|
return ret;
|
|
}
|
|
|
|
kobject_uevent(&q->kobj, KOBJ_ADD);
|
|
|
|
if (q->mq_ops)
|
|
blk_mq_register_disk(disk);
|
|
|
|
if (!q->request_fn)
|
|
return 0;
|
|
|
|
ret = elv_register_queue(q);
|
|
if (ret) {
|
|
kobject_uevent(&q->kobj, KOBJ_REMOVE);
|
|
kobject_del(&q->kobj);
|
|
blk_trace_remove_sysfs(dev);
|
|
kobject_put(&dev->kobj);
|
|
return ret;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
void blk_unregister_queue(struct gendisk *disk)
|
|
{
|
|
struct request_queue *q = disk->queue;
|
|
|
|
if (WARN_ON(!q))
|
|
return;
|
|
|
|
if (q->mq_ops)
|
|
blk_mq_unregister_disk(disk);
|
|
|
|
if (q->request_fn)
|
|
elv_unregister_queue(q);
|
|
|
|
kobject_uevent(&q->kobj, KOBJ_REMOVE);
|
|
kobject_del(&q->kobj);
|
|
blk_trace_remove_sysfs(disk_to_dev(disk));
|
|
kobject_put(&disk_to_dev(disk)->kobj);
|
|
}
|