linux-2.6.25/blk_queue_make_request() の履歴(No.96)

参照元†

linux-2.6.25/blk_plug_device()

↑

説明†

パス: linux-2.6.25/block/blk-settings.c

FIXME: これは何？
- 説明

↑

引数†

struct request_queue *q
make_request_fn *mfn

↑

返り値†

なし

↑

参考†

なし

↑

実装†

/**
 * blk_queue_make_request - define an alternate make_request function for a device
 * @q:  the request queue for the device to be affected
 * @mfn: the alternate make_request function
 *
 * Description:
 *    The normal way for &struct bios to be passed to a device
 *    driver is for them to be collected into requests on a request
 *    queue, and then to allow the device driver to select requests
 *    off that queue when it is ready.  This works well for many block
 *    devices. However some block devices (typically virtual devices
 *    such as md or lvm) do not benefit from the processing on the
 *    request queue, and are served best by having the requests passed
 *    directly to them.  This can be achieved by providing a function
 *    to blk_queue_make_request().
 *
 * Caveat:
 *    The driver that does this *must* be able to deal appropriately
 *    with buffers in "highmemory". This can be accomplished by either calling
 *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
 *    blk_queue_bounce() to create a buffer in normal memory.
 **/
void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
{
        /*
         * set defaults
         */
        q->nr_requests = BLKDEV_MAX_RQ;
        blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
        blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
        q->make_request_fn = mfn;
        q->backing_dev_info.ra_pages =
                        (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
        q->backing_dev_info.state = 0;
        q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
        blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
        blk_queue_hardsect_size(q, 512);
        blk_queue_dma_alignment(q, 511);
        blk_queue_congestion_threshold(q);
        q->nr_batching = BLK_BATCH_REQ;

        q->unplug_thresh = 4;           /* hmm */
        q->unplug_delay = (3 * HZ) / 1000;      /* 3 milliseconds */
        if (q->unplug_delay == 0)
                q->unplug_delay = 1;

        INIT_WORK(&q->unplug_work, blk_unplug_work);

        q->unplug_timer.function = blk_unplug_timeout;
        q->unplug_timer.data = (unsigned long)q;

        /*
         * by default assume old behaviour and bounce for any highmem page
         */
        blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
}
EXPORT_SYMBOL(blk_queue_make_request);

↑

linux-2.6.25/blk_queue_make_request() の履歴(No.96)

参照元†

説明†

引数†

返り値†

参考†

実装†

コメント†