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![Jens Axboe](/assets/img/avatar_default.png)
For sync IO, we'll often do them serialized. This means we'll be touching the queue timer for every IO, as opposed to only occasionally like we do for queued IO. Instead of deleting the timer when the last request is removed, just let continue running. If a new request comes up soon we then don't have to readd the timer again. If no new requests arrive, the timer will expire without side effect later. This improves high iops sync IO by ~1%. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
223 lines
5.3 KiB
C
223 lines
5.3 KiB
C
/*
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* Functions related to generic timeout handling of requests.
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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/blkdev.h>
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#include <linux/fault-inject.h>
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#include "blk.h"
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#ifdef CONFIG_FAIL_IO_TIMEOUT
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static DECLARE_FAULT_ATTR(fail_io_timeout);
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static int __init setup_fail_io_timeout(char *str)
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{
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return setup_fault_attr(&fail_io_timeout, str);
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}
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__setup("fail_io_timeout=", setup_fail_io_timeout);
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int blk_should_fake_timeout(struct request_queue *q)
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{
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if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
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return 0;
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return should_fail(&fail_io_timeout, 1);
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}
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static int __init fail_io_timeout_debugfs(void)
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{
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return init_fault_attr_dentries(&fail_io_timeout, "fail_io_timeout");
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}
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late_initcall(fail_io_timeout_debugfs);
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ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct gendisk *disk = dev_to_disk(dev);
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int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
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return sprintf(buf, "%d\n", set != 0);
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}
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ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct gendisk *disk = dev_to_disk(dev);
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int val;
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if (count) {
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struct request_queue *q = disk->queue;
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char *p = (char *) buf;
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val = simple_strtoul(p, &p, 10);
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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_FAIL_IO, q);
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else
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queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
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spin_unlock_irq(q->queue_lock);
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}
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return count;
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}
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#endif /* CONFIG_FAIL_IO_TIMEOUT */
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/*
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* blk_delete_timer - Delete/cancel timer for a given function.
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* @req: request that we are canceling timer for
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*
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*/
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void blk_delete_timer(struct request *req)
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{
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list_del_init(&req->timeout_list);
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}
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static void blk_rq_timed_out(struct request *req)
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{
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struct request_queue *q = req->q;
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enum blk_eh_timer_return ret;
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ret = q->rq_timed_out_fn(req);
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switch (ret) {
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case BLK_EH_HANDLED:
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__blk_complete_request(req);
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break;
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case BLK_EH_RESET_TIMER:
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blk_clear_rq_complete(req);
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blk_add_timer(req);
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break;
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case BLK_EH_NOT_HANDLED:
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/*
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* LLD handles this for now but in the future
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* we can send a request msg to abort the command
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* and we can move more of the generic scsi eh code to
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* the blk layer.
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*/
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break;
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default:
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printk(KERN_ERR "block: bad eh return: %d\n", ret);
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break;
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}
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}
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void blk_rq_timed_out_timer(unsigned long data)
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{
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struct request_queue *q = (struct request_queue *) data;
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unsigned long flags, next = 0;
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struct request *rq, *tmp;
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spin_lock_irqsave(q->queue_lock, flags);
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list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
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if (time_after_eq(jiffies, rq->deadline)) {
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list_del_init(&rq->timeout_list);
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/*
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* Check if we raced with end io completion
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*/
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if (blk_mark_rq_complete(rq))
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continue;
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blk_rq_timed_out(rq);
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} else {
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if (!next || time_after(next, rq->deadline))
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next = rq->deadline;
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}
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}
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/*
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* next can never be 0 here with the list non-empty, since we always
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* bump ->deadline to 1 so we can detect if the timer was ever added
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* or not. See comment in blk_add_timer()
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*/
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if (next)
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mod_timer(&q->timeout, round_jiffies_up(next));
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spin_unlock_irqrestore(q->queue_lock, flags);
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}
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/**
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* blk_abort_request -- Request request recovery for the specified command
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* @req: pointer to the request of interest
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*
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* This function requests that the block layer start recovery for the
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* request by deleting the timer and calling the q's timeout function.
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* LLDDs who implement their own error recovery MAY ignore the timeout
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* event if they generated blk_abort_req. Must hold queue lock.
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*/
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void blk_abort_request(struct request *req)
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{
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if (blk_mark_rq_complete(req))
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return;
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blk_delete_timer(req);
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blk_rq_timed_out(req);
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}
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EXPORT_SYMBOL_GPL(blk_abort_request);
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/**
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* blk_add_timer - Start timeout timer for a single request
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* @req: request that is about to start running.
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*
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* Notes:
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* Each request has its own timer, and as it is added to the queue, we
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* set up the timer. When the request completes, we cancel the timer.
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*/
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void blk_add_timer(struct request *req)
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{
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struct request_queue *q = req->q;
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unsigned long expiry;
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if (!q->rq_timed_out_fn)
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return;
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BUG_ON(!list_empty(&req->timeout_list));
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BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
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if (req->timeout)
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req->deadline = jiffies + req->timeout;
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else {
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req->deadline = jiffies + q->rq_timeout;
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/*
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* Some LLDs, like scsi, peek at the timeout to prevent
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* a command from being retried forever.
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*/
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req->timeout = q->rq_timeout;
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}
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list_add_tail(&req->timeout_list, &q->timeout_list);
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/*
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* If the timer isn't already pending or this timeout is earlier
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* than an existing one, modify the timer. Round up to next nearest
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* second.
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*/
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expiry = round_jiffies_up(req->deadline);
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if (!timer_pending(&q->timeout) ||
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time_before(expiry, q->timeout.expires))
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mod_timer(&q->timeout, expiry);
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}
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/**
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* blk_abort_queue -- Abort all request on given queue
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* @queue: pointer to queue
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*
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*/
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void blk_abort_queue(struct request_queue *q)
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{
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unsigned long flags;
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struct request *rq, *tmp;
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spin_lock_irqsave(q->queue_lock, flags);
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elv_abort_queue(q);
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list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
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blk_abort_request(rq);
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spin_unlock_irqrestore(q->queue_lock, flags);
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}
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EXPORT_SYMBOL_GPL(blk_abort_queue);
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