On Wed, Sep 10, 2008 at 12:51 AM, Rohit Sharma <imreckless@xxxxxxxxx> wrote:
> I was going through block drivers,
> i am not able to associate request queues and bio structures.
> How are the requests processed using bio structures.
> Can anyone provide me with block driver example or tutorial.
>
looking at block/scsi_ioctl.c:sg_io() function - does line 207 and 241
answer your question?
207 rq = blk_get_request(q, writing ? WRITE : READ, GFP_KERNEL);
208 if (!rq)
209 return -ENOMEM;
210
211 if (blk_fill_sghdr_rq(q, rq, hdr, file)) {
212 blk_put_request(rq);
213 return -EFAULT;
214 }
215
216 if (hdr->iovec_count) {
217 const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
218 struct sg_iovec *iov;
219
220 iov = kmalloc(size, GFP_KERNEL);
221 if (!iov) {
222 ret = -ENOMEM;
223 goto out;
224 }
225
226 if (copy_from_user(iov, hdr->dxferp, size)) {
227 kfree(iov);
228 ret = -EFAULT;
229 goto out;
230 }
231
232 ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count,
233 hdr->dxfer_len);
234 kfree(iov);
235 } else if (hdr->dxfer_len)
236 ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
237
238 if (ret)
239 goto out;
240
241 bio = rq->bio;
242 memset(sense, 0, sizeof(sense));
243 rq->sense = sense;
244 rq->sense_len = 0;
245 rq->retries = 0;
246
247 start_time = jiffies;
248
249 /* ignore return value. All information is passed back to caller
250 * (if he doesn't check that is his problem).
251 * N.B. a non-zero SCSI status is _not_ necessarily an error.
252 */
253 blk_execute_rq(q, bd_disk, rq, 0);
254
255 hdr->duration = jiffies_to_msecs(jiffies - start_time);
256
257 return blk_complete_sghdr_rq(rq, hdr, bio);
--
Regards,
Peter Teoh
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