Quelle blk-timeout.c Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
* Functions related to generic timeout handling of requests.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/fault-inject.h>

#include "blk.h"
#include "blk-mq.h"

#ifdef CONFIG_FAIL_IO_TIMEOUT

static DECLARE_FAULT_ATTR(fail_io_timeout);

static int __init setup_fail_io_timeout(char *str)
{
return setup_fault_attr(&fail_io_timeout, str);
}
__setup("fail_io_timeout=", setup_fail_io_timeout);

bool __blk_should_fake_timeout(struct request_queue *q)
{
return should_fail(&fail_io_timeout, 1);
}
EXPORT_SYMBOL_GPL(__blk_should_fake_timeout);

static int __init fail_io_timeout_debugfs(void)
{
struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
      NULL, &fail_io_timeout);

return PTR_ERR_OR_ZERO(dir);
}

late_initcall(fail_io_timeout_debugfs);

ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
     char *buf)
{
struct gendisk *disk = dev_to_disk(dev);
int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);

return sprintf(buf, "%d\n", set != 0);
}

ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
      const char *buf, size_t count)
{
struct gendisk *disk = dev_to_disk(dev);
int val;

if (count) {
  struct request_queue *q = disk->queue;
  char *p = (char *) buf;

  val = simple_strtoul(p, &p, 10);
  if (val)
   blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  else
   blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
}

return count;
}

#endif /* CONFIG_FAIL_IO_TIMEOUT */

/**
* blk_abort_request - Request recovery for the specified command
* @req: pointer to the request of interest
*
* This function requests that the block layer start recovery for the
* request by deleting the timer and calling the q's timeout function.
* LLDDs who implement their own error recovery MAY ignore the timeout
* event if they generated blk_abort_request.
*/
void blk_abort_request(struct request *req)
{
/*
* All we need to ensure is that timeout scan takes place
* immediately and that scan sees the new timeout value.
* No need for fancy synchronizations.
*/
WRITE_ONCE(req->deadline, jiffies);
kblockd_schedule_work(&req->q->timeout_work);
}
EXPORT_SYMBOL_GPL(blk_abort_request);

static unsigned long blk_timeout_mask __read_mostly;

static int __init blk_timeout_init(void)
{
blk_timeout_mask = roundup_pow_of_two(HZ) - 1;
return 0;
}

late_initcall(blk_timeout_init);

/*
* Just a rough estimate, we don't care about specific values for timeouts.
*/
static inline unsigned long blk_round_jiffies(unsigned long j)
{
return (j + blk_timeout_mask) + 1;
}

unsigned long blk_rq_timeout(unsigned long timeout)
{
unsigned long maxt;

maxt = blk_round_jiffies(jiffies + BLK_MAX_TIMEOUT);
if (time_after(timeout, maxt))
  timeout = maxt;

return timeout;
}

/**
* blk_add_timer - Start timeout timer for a single request
* @req: request that is about to start running.
*
* Notes:
*    Each request has its own timer, and as it is added to the queue, we
*    set up the timer. When the request completes, we cancel the timer.
*/
void blk_add_timer(struct request *req)
{
struct request_queue *q = req->q;
unsigned long expiry;

/*
* Some LLDs, like scsi, peek at the timeout to prevent a
* command from being retried forever.
*/
if (!req->timeout)
  req->timeout = q->rq_timeout;

req->rq_flags &= ~RQF_TIMED_OUT;

expiry = jiffies + req->timeout;
WRITE_ONCE(req->deadline, expiry);

/*
* If the timer isn't already pending or this timeout is earlier
* than an existing one, modify the timer. Round up to next nearest
* second.
*/
expiry = blk_rq_timeout(blk_round_jiffies(expiry));

if (!timer_pending(&q->timeout) ||
     time_before(expiry, q->timeout.expires)) {
  unsigned long diff = q->timeout.expires - expiry;

  /*
* Due to added timer slack to group timers, the timer
* will often be a little in front of what we asked for.
* So apply some tolerance here too, otherwise we keep
* modifying the timer because expires for value X
* will be X + something.
*/
  if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
   mod_timer(&q->timeout, expiry);
}

}

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