blk-exec.c

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/*
 * Functions related to setting various queue properties from drivers
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>

#include "blk.h"

/*
 * for max sense size
 */
#include <scsi/scsi_cmnd.h>

static void blk_end_sync_rq(struct request *rq, int error)
{
    struct completion *waiting = rq->end_io_data;

    rq->end_io_data = NULL;
    __blk_put_request(rq->q, rq);

    /*
     * complete last, if this is a stack request the process (and thus
     * the rq pointer) could be invalid right after this complete()
     */
    complete(waiting);
}

void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
               struct request *rq, int at_head,
               rq_end_io_fn *done)
{
    int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
    bool is_pm_resume;

    WARN_ON(irqs_disabled());

    rq->rq_disk = bd_disk;
    rq->end_io = done;
    /*
     * need to check this before __blk_run_queue(), because rq can
     * be freed before that returns.
     */
    is_pm_resume = rq->cmd_type == REQ_TYPE_PM_RESUME;

    spin_lock_irq(q->queue_lock);

    if (unlikely(blk_queue_dead(q))) {
        rq->errors = -ENXIO;
        if (rq->end_io)
            rq->end_io(rq, rq->errors);
        spin_unlock_irq(q->queue_lock);
        return;
    }

    __elv_add_request(q, rq, where);
    __blk_run_queue(q);
    /* the queue is stopped so it won't be run */
    if (is_pm_resume)
        q->request_fn(q);
    spin_unlock_irq(q->queue_lock);
}
EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);

int blk_execute_rq(struct request_queue *q, struct gendisk *bd_disk,
           struct request *rq, int at_head)
{
    DECLARE_COMPLETION_ONSTACK(wait);
    char sense[SCSI_SENSE_BUFFERSIZE];
    int err = 0;
    unsigned long hang_check;

    /*
     * we need an extra reference to the request, so we can look at
     * it after io completion
     */
    rq->ref_count++;

    if (!rq->sense) {
        memset(sense, 0, sizeof(sense));
        rq->sense = sense;
        rq->sense_len = 0;
    }

    rq->end_io_data = &wait;
    blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);

    /* Prevent hang_check timer from firing at us during very long I/O */
    hang_check = sysctl_hung_task_timeout_secs;
    if (hang_check)
        while (!wait_for_completion_timeout(&wait, hang_check * (HZ/2)));
    else
        wait_for_completion(&wait);

    if (rq->errors)
        err = -EIO;

    return err;
}
EXPORT_SYMBOL(blk_execute_rq);