Timer context is not very useful for drivers to perform any meaningful abort action from. So instead of calling the driver from this useless context defer it to a workqueue as soon as possible. Note that while a delayed_work item would seem the right thing here I didn't dare to use it due to the magic in blk_add_timer that pokes deep into timer internals. But maybe this encourages Tejun to add a sensible API for that to the workqueue API and we'll all be fine in the end :) Contains a major update from Keith Bush: "This patch removes synchronizing the timeout work so that the timer can start a freeze on its own queue. The timer enters the queue, so timer context can only start a freeze, but not wait for frozen." Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Keith Busch <keith.busch@intel.com> Signed-off-by: Jens Axboe <axboe@fb.com>
247 lines
6 KiB
C
247 lines
6 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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#include "blk-mq.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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struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
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NULL, &fail_io_timeout);
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return PTR_ERR_OR_ZERO(dir);
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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 = BLK_EH_RESET_TIMER;
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if (q->rq_timed_out_fn)
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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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/* Can we use req->errors here? */
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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_add_timer(req);
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blk_clear_rq_complete(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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static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
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unsigned int *next_set)
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{
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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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blk_rq_timed_out(rq);
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} else if (!*next_set || time_after(*next_timeout, rq->deadline)) {
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*next_timeout = rq->deadline;
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*next_set = 1;
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}
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}
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void blk_timeout_work(struct work_struct *work)
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{
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struct request_queue *q =
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container_of(work, struct request_queue, timeout_work);
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unsigned long flags, next = 0;
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struct request *rq, *tmp;
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int next_set = 0;
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if (blk_queue_enter(q, true))
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return;
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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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blk_rq_check_expired(rq, &next, &next_set);
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if (next_set)
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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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blk_queue_exit(q);
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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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if (req->q->mq_ops) {
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blk_mq_rq_timed_out(req, false);
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} else {
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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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}
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EXPORT_SYMBOL_GPL(blk_abort_request);
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unsigned long blk_rq_timeout(unsigned long timeout)
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{
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unsigned long maxt;
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maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
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if (time_after(timeout, maxt))
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timeout = maxt;
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return timeout;
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}
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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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* Queue lock must be held for the non-mq case, mq case doesn't care.
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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 (req->cmd_flags & REQ_NO_TIMEOUT)
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return;
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/* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
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if (!q->mq_ops && !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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/*
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* Some LLDs, like scsi, peek at the timeout to prevent a
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* command from being retried forever.
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*/
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if (!req->timeout)
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req->timeout = q->rq_timeout;
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req->deadline = jiffies + req->timeout;
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/*
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* Only the non-mq case needs to add the request to a protected list.
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* For the mq case we simply scan the tag map.
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*/
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if (!q->mq_ops)
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list_add_tail(&req->timeout_list, &req->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 = blk_rq_timeout(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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unsigned long diff = q->timeout.expires - expiry;
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/*
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* Due to added timer slack to group timers, the timer
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* will often be a little in front of what we asked for.
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* So apply some tolerance here too, otherwise we keep
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* modifying the timer because expires for value X
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* will be X + something.
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*/
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if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
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mod_timer(&q->timeout, expiry);
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}
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}
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