scsi_lib.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,742 行 · 第 1/4 页

		blk_run_queue(sdev->request_queue);

		spin_lock_irqsave(shost->host_lock, flags);
		if (unlikely(!list_empty(&sdev->starved_entry)))
			/*
			 * sdev lost a race, and was put back on the
			 * starved list. This is unlikely but without this
			 * in theory we could loop forever.
			 */
			break;
	}
	spin_unlock_irqrestore(shost->host_lock, flags);

	blk_run_queue(q);
}

/*
 * Function:	scsi_requeue_command()
 *
 * Purpose:	Handle post-processing of completed commands.
 *
 * Arguments:	q	- queue to operate on
 *		cmd	- command that may need to be requeued.
 *
 * Returns:	Nothing
 *
 * Notes:	After command completion, there may be blocks left
 *		over which weren't finished by the previous command
 *		this can be for a number of reasons - the main one is
 *		I/O errors in the middle of the request, in which case
 *		we need to request the blocks that come after the bad
 *		sector.
 */
static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
{
	cmd->request->flags &= ~REQ_DONTPREP;
	blk_insert_request(q, cmd->request, 1, cmd, 1);

	scsi_run_queue(q);
}

void scsi_next_command(struct scsi_cmnd *cmd)
{
	struct request_queue *q = cmd->device->request_queue;

	scsi_put_command(cmd);
	scsi_run_queue(q);
}

void scsi_run_host_queues(struct Scsi_Host *shost)
{
	struct scsi_device *sdev;

	shost_for_each_device(sdev, shost)
		scsi_run_queue(sdev->request_queue);
}

/*
 * Function:    scsi_end_request()
 *
 * Purpose:     Post-processing of completed commands called from interrupt
 *              handler or a bottom-half handler.
 *
 * Arguments:   cmd	 - command that is complete.
 *              uptodate - 1 if I/O indicates success, 0 for I/O error.
 *              sectors  - number of sectors we want to mark.
 *		requeue  - indicates whether we should requeue leftovers.
 *		frequeue - indicates that if we release the command block
 *			   that the queue request function should be called.
 *
 * Lock status: Assumed that lock is not held upon entry.
 *
 * Returns:     Nothing
 *
 * Notes:       This is called for block device requests in order to
 *              mark some number of sectors as complete.
 * 
 *		We are guaranteeing that the request queue will be goosed
 *		at some point during this call.
 */
static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int uptodate,
					  int bytes, int requeue)
{
	request_queue_t *q = cmd->device->request_queue;
	struct request *req = cmd->request;
	unsigned long flags;

	/*
	 * If there are blocks left over at the end, set up the command
	 * to queue the remainder of them.
	 */
	if (end_that_request_chunk(req, uptodate, bytes)) {
		int leftover = (req->hard_nr_sectors << 9);

		if (blk_pc_request(req))
			leftover = req->data_len;

		/* kill remainder if no retrys */
		if (!uptodate && blk_noretry_request(req))
			end_that_request_chunk(req, 0, leftover);
		else {
			if (requeue)
				/*
				 * Bleah.  Leftovers again.  Stick the
				 * leftovers in the front of the
				 * queue, and goose the queue again.
				 */
				scsi_requeue_command(q, cmd);

			return cmd;
		}
	}

	add_disk_randomness(req->rq_disk);

	spin_lock_irqsave(q->queue_lock, flags);
	if (blk_rq_tagged(req))
		blk_queue_end_tag(q, req);
	end_that_request_last(req);
	spin_unlock_irqrestore(q->queue_lock, flags);

	/*
	 * This will goose the queue request function at the end, so we don't
	 * need to worry about launching another command.
	 */
	scsi_next_command(cmd);
	return NULL;
}

static struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, int gfp_mask)
{
	struct scsi_host_sg_pool *sgp;
	struct scatterlist *sgl;

	BUG_ON(!cmd->use_sg);

	switch (cmd->use_sg) {
	case 1 ... 8:
		cmd->sglist_len = 0;
		break;
	case 9 ... 16:
		cmd->sglist_len = 1;
		break;
	case 17 ... 32:
		cmd->sglist_len = 2;
		break;
#if (SCSI_MAX_PHYS_SEGMENTS > 32)
	case 33 ... 64:
		cmd->sglist_len = 3;
		break;
#if (SCSI_MAX_PHYS_SEGMENTS > 64)
	case 65 ... 128:
		cmd->sglist_len = 4;
		break;
#if (SCSI_MAX_PHYS_SEGMENTS  > 128)
	case 129 ... 256:
		cmd->sglist_len = 5;
		break;
#endif
#endif
#endif
	default:
		return NULL;
	}

	sgp = scsi_sg_pools + cmd->sglist_len;
	sgl = mempool_alloc(sgp->pool, gfp_mask);
	if (sgl)
		memset(sgl, 0, sgp->size);
	return sgl;
}

static void scsi_free_sgtable(struct scatterlist *sgl, int index)
{
	struct scsi_host_sg_pool *sgp;

	BUG_ON(index > SG_MEMPOOL_NR);

	sgp = scsi_sg_pools + index;
	mempool_free(sgl, sgp->pool);
}

/*
 * Function:    scsi_release_buffers()
 *
 * Purpose:     Completion processing for block device I/O requests.
 *
 * Arguments:   cmd	- command that we are bailing.
 *
 * Lock status: Assumed that no lock is held upon entry.
 *
 * Returns:     Nothing
 *
 * Notes:       In the event that an upper level driver rejects a
 *		command, we must release resources allocated during
 *		the __init_io() function.  Primarily this would involve
 *		the scatter-gather table, and potentially any bounce
 *		buffers.
 */
static void scsi_release_buffers(struct scsi_cmnd *cmd)
{
	struct request *req = cmd->request;

	/*
	 * Free up any indirection buffers we allocated for DMA purposes. 
	 */
	if (cmd->use_sg)
		scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
	else if (cmd->request_buffer != req->buffer)
		kfree(cmd->request_buffer);

	/*
	 * Zero these out.  They now point to freed memory, and it is
	 * dangerous to hang onto the pointers.
	 */
	cmd->buffer  = NULL;
	cmd->bufflen = 0;
	cmd->request_buffer = NULL;
	cmd->request_bufflen = 0;
}

/*
 * Function:    scsi_io_completion()
 *
 * Purpose:     Completion processing for block device I/O requests.
 *
 * Arguments:   cmd   - command that is finished.
 *
 * Lock status: Assumed that no lock is held upon entry.
 *
 * Returns:     Nothing
 *
 * Notes:       This function is matched in terms of capabilities to
 *              the function that created the scatter-gather list.
 *              In other words, if there are no bounce buffers
 *              (the normal case for most drivers), we don't need
 *              the logic to deal with cleaning up afterwards.
 *
 *		We must do one of several things here:
 *
 *		a) Call scsi_end_request.  This will finish off the
 *		   specified number of sectors.  If we are done, the
 *		   command block will be released, and the queue
 *		   function will be goosed.  If we are not done, then
 *		   scsi_end_request will directly goose the queue.
 *
 *		b) We can just use scsi_requeue_command() here.  This would
 *		   be used if we just wanted to retry, for example.
 */
void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes,
			unsigned int block_bytes)
{
	int result = cmd->result;
	int this_count = cmd->bufflen;
	request_queue_t *q = cmd->device->request_queue;
	struct request *req = cmd->request;
	int clear_errors = 1;

	/*
	 * Free up any indirection buffers we allocated for DMA purposes. 
	 * For the case of a READ, we need to copy the data out of the
	 * bounce buffer and into the real buffer.
	 */
	if (cmd->use_sg)
		scsi_free_sgtable(cmd->buffer, cmd->sglist_len);
	else if (cmd->buffer != req->buffer) {
		if (rq_data_dir(req) == READ) {
			unsigned long flags;
			char *to = bio_kmap_irq(req->bio, &flags);
			memcpy(to, cmd->buffer, cmd->bufflen);
			bio_kunmap_irq(to, &flags);
		}
		kfree(cmd->buffer);
	}

	if (blk_pc_request(req)) { /* SG_IO ioctl from block level */
		req->errors = (driver_byte(result) & DRIVER_SENSE) ?
			      (CHECK_CONDITION << 1) : (result & 0xff);
		if (result) {
			clear_errors = 0;
			if (cmd->sense_buffer[0] & 0x70) {
				int len = 8 + cmd->sense_buffer[7];

				if (len > SCSI_SENSE_BUFFERSIZE)
					len = SCSI_SENSE_BUFFERSIZE;
				memcpy(req->sense, cmd->sense_buffer,  len);
				req->sense_len = len;
			}
		} else
			req->data_len -= cmd->bufflen;
	}

	/*
	 * Zero these out.  They now point to freed memory, and it is
	 * dangerous to hang onto the pointers.
	 */
	cmd->buffer  = NULL;
	cmd->bufflen = 0;
	cmd->request_buffer = NULL;
	cmd->request_bufflen = 0;

	/*
	 * Next deal with any sectors which we were able to correctly
	 * handle.
	 */
	if (good_bytes >= 0) {
		SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, %d bytes done.\n",
					      req->nr_sectors, good_bytes));
		SCSI_LOG_HLCOMPLETE(1, printk("use_sg is %d\n", cmd->use_sg));

		if (clear_errors)
			req->errors = 0;
		/*
		 * If multiple sectors are requested in one buffer, then
		 * they will have been finished off by the first command.
		 * If not, then we have a multi-buffer command.
		 *
		 * If block_bytes != 0, it means we had a medium error
		 * of some sort, and that we want to mark some number of
		 * sectors as not uptodate.  Thus we want to inhibit
		 * requeueing right here - we will requeue down below
		 * when we handle the bad sectors.
		 */
		cmd = scsi_end_request(cmd, 1, good_bytes, result == 0);

		/*
		 * If the command completed without error, then either finish off the
		 * rest of the command, or start a new one.
		 */
		if (result == 0 || cmd == NULL ) {
			return;
		}
	}
	/*
	 * Now, if we were good little boys and girls, Santa left us a request
	 * sense buffer.  We can extract information from this, so we
	 * can choose a block to remap, etc.
	 */
	if (driver_byte(result) != 0) {
		if ((cmd->sense_buffer[0] & 0x7f) == 0x70) {
			/*
			 * If the device is in the process of becoming ready,
			 * retry.
			 */
			if (cmd->sense_buffer[12] == 0x04 &&
			    cmd->sense_buffer[13] == 0x01) {
				scsi_requeue_command(q, cmd);
				return;
			}
			if ((cmd->sense_buffer[2] & 0xf) == UNIT_ATTENTION) {
				if (cmd->device->removable) {
					/* detected disc change.  set a bit 
					 * and quietly refuse further access.
		 			 */
					cmd->device->changed = 1;
					cmd = scsi_end_request(cmd, 0,
							this_count, 1);
					return;
				} else {
					/*
				 	* Must have been a power glitch, or a
				 	* bus reset.  Could not have been a
				 	* media change, so we just retry the
				 	* request and see what happens.  
				 	*/
					scsi_requeue_command(q, cmd);
					return;
				}
			}
		}
		/*
		 * If we had an ILLEGAL REQUEST returned, then we may have
		 * performed an unsupported command.  The only thing this
		 * should be would be a ten byte read where only a six byte
		 * read was supported.  Also, on a system where READ CAPACITY
		 * failed, we may have read past the end of the disk.
		 */

		switch (cmd->sense_buffer[2]) {
		case ILLEGAL_REQUEST:
			if (cmd->device->use_10_for_rw &&
			    (cmd->cmnd[0] == READ_10 ||
			     cmd->cmnd[0] == WRITE_10)) {
				cmd->device->use_10_for_rw = 0;
				/*
				 * This will cause a retry with a 6-byte
				 * command.
				 */
				scsi_requeue_command(q, cmd);
				result = 0;
			} else {
				cmd = scsi_end_request(cmd, 0, this_count, 1);
				return;
			}
			break;
		case NOT_READY:
			printk(KERN_INFO "Device %s not ready.\n",
			       req->rq_disk ? req->rq_disk->disk_name : "");
			cmd = scsi_end_request(cmd, 0, this_count, 1);
			return;
			break;
		case MEDIUM_ERROR:
		case VOLUME_OVERFLOW:
			printk("scsi%d: ERROR on channel %d, id %d, lun %d, CDB: ",
			       cmd->device->host->host_no, (int) cmd->device->channel,
			       (int) cmd->device->id, (int) cmd->device->lun);
			__scsi_print_command(cmd->data_cmnd);
			scsi_print_sense("", cmd);
			cmd = scsi_end_request(cmd, 0, block_bytes, 1);
			return;
		default:
			break;
		}
	}			/* driver byte != 0 */
	if (host_byte(result) == DID_RESET) {
		/*
		 * Third party bus reset or reset for error
		 * recovery reasons.  Just retry the request
		 * and see what happens.  
		 */
		scsi_requeue_command(q, cmd);
		return;
	}
	if (result) {
		printk("SCSI error : <%d %d %d %d> return code = 0x%x\n",
		       cmd->device->host->host_no,
		       cmd->device->channel,
		       cmd->device->id,
		       cmd->device->lun, result);

		if (driver_byte(result) & DRIVER_SENSE)
			scsi_print_sense("", cmd);
		/*
		 * Mark a single buffer as not uptodate.  Queue the remainder.
		 * We sometimes get this cruft in the event that a medium error