scsi_lib.c

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	 * If there are blocks left over at the end, set up the command
	 * to queue the remainder of them.
	 */
	if (req->bh) {
                request_queue_t *q;

		if( !requeue )
		{
			return SCpnt;
		}

                q = &SCpnt->device->request_queue;

		req->buffer = bh->b_data;
		/*
		 * Bleah.  Leftovers again.  Stick the leftovers in
		 * the front of the queue, and goose the queue again.
		 */
		scsi_queue_next_request(q, SCpnt);
		return SCpnt;
	}
	/*
	 * This request is done.  If there is someone blocked waiting for this
	 * request, wake them up.  Typically used to wake up processes trying
	 * to swap a page into memory.
	 */
	if (req->waiting != NULL) {
		complete(req->waiting);
	}
	add_blkdev_randomness(MAJOR(req->rq_dev));

        SDpnt = SCpnt->device;

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

	if( frequeue ) {
		request_queue_t *q;

		q = &SDpnt->request_queue;
		scsi_queue_next_request(q, NULL);                
	}
	return NULL;
}

/*
 * Function:    scsi_end_request()
 *
 * Purpose:     Post-processing of completed commands called from interrupt
 *              handler or a bottom-half handler.
 *
 * Arguments:   SCpnt    - command that is complete.
 *              uptodate - 1 if I/O indicates success, 0 for I/O error.
 *              sectors  - number of sectors we want to mark.
 *
 * 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.
 */
Scsi_Cmnd *scsi_end_request(Scsi_Cmnd * SCpnt, int uptodate, int sectors)
{
	return __scsi_end_request(SCpnt, uptodate, sectors, 1, 1);
}

/*
 * Function:    scsi_release_buffers()
 *
 * Purpose:     Completion processing for block device I/O requests.
 *
 * Arguments:   SCpnt   - 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(Scsi_Cmnd * SCpnt)
{
	ASSERT_LOCK(&io_request_lock, 0);

	/*
	 * Free up any indirection buffers we allocated for DMA purposes. 
	 */
	if (SCpnt->use_sg) {
		struct scatterlist *sgpnt;
		void **bbpnt;
		int i;

		sgpnt = (struct scatterlist *) SCpnt->request_buffer;
		bbpnt = SCpnt->bounce_buffers;

		if (bbpnt) {
			for (i = 0; i < SCpnt->use_sg; i++) {
				if (bbpnt[i])
					scsi_free(sgpnt[i].address, sgpnt[i].length);
			}
		}
		scsi_free(SCpnt->request_buffer, SCpnt->sglist_len);
	} else {
		if (SCpnt->request_buffer != SCpnt->request.buffer) {
			scsi_free(SCpnt->request_buffer, SCpnt->request_bufflen);
		}
	}

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

/*
 * Function:    scsi_io_completion()
 *
 * Purpose:     Completion processing for block device I/O requests.
 *
 * Arguments:   SCpnt   - 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.
 */
void scsi_io_completion(Scsi_Cmnd * SCpnt, int good_sectors,
			int block_sectors)
{
	int result = SCpnt->result;
	int this_count = SCpnt->bufflen >> 9;
	request_queue_t *q = &SCpnt->device->request_queue;

	/*
	 * We must do one of several things here:
	 *
	 *	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.
	 *
	 *	We can just use scsi_queue_next_request() here.  This
	 *	would be used if we just wanted to retry, for example.
	 *
	 */
	ASSERT_LOCK(&io_request_lock, 0);

	/*
	 * 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 (SCpnt->use_sg) {
		struct scatterlist *sgpnt;
		void **bbpnt;
		int i;

		sgpnt = (struct scatterlist *) SCpnt->buffer;
		bbpnt = SCpnt->bounce_buffers;

		if (bbpnt) {
			for (i = 0; i < SCpnt->use_sg; i++) {
				if (bbpnt[i]) {
					if (SCpnt->request.cmd == READ) {
						memcpy(bbpnt[i],
						       sgpnt[i].address,
						       sgpnt[i].length);
					}
					scsi_free(sgpnt[i].address, sgpnt[i].length);
				}
			}
		}
		scsi_free(SCpnt->buffer, SCpnt->sglist_len);
	} else {
		if (SCpnt->buffer != SCpnt->request.buffer) {
			if (SCpnt->request.cmd == READ) {
				memcpy(SCpnt->request.buffer, SCpnt->buffer,
				       SCpnt->bufflen);
			}
			scsi_free(SCpnt->buffer, SCpnt->bufflen);
		}
	}

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

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

		SCpnt->request.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_sectors != 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.
		 */
		SCpnt = __scsi_end_request(SCpnt, 
					   1, 
					   good_sectors,
					   result == 0,
					   1);

		/*
		 * If the command completed without error, then either finish off the
		 * rest of the command, or start a new one.
		 */
		if (result == 0 || SCpnt == 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 (suggestion(result) == SUGGEST_REMAP) {
#ifdef REMAP
			/*
			 * Not yet implemented.  A read will fail after being remapped,
			 * a write will call the strategy routine again.
			 */
			if (SCpnt->device->remap) {
				result = 0;
			}
#endif
		}
		if ((SCpnt->sense_buffer[0] & 0x7f) == 0x70) {
			/*
			 * If the device is in the process of becoming ready,
			 * retry.
			 */
			if (SCpnt->sense_buffer[12] == 0x04 &&
			    SCpnt->sense_buffer[13] == 0x01) {
				scsi_queue_next_request(q, SCpnt);
				return;
			}
			if ((SCpnt->sense_buffer[2] & 0xf) == UNIT_ATTENTION) {
				if (SCpnt->device->removable) {
					/* detected disc change.  set a bit 
					 * and quietly refuse further access.
		 			 */
					SCpnt->device->changed = 1;
					SCpnt = scsi_end_request(SCpnt, 0, this_count);
					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_queue_next_request(q, SCpnt);
					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 have have read
		 * past the end of the disk.
		 */

		switch (SCpnt->sense_buffer[2]) {
		case ILLEGAL_REQUEST:
			if (SCpnt->device->ten) {
				SCpnt->device->ten = 0;
				/*
				 * This will cause a retry with a 6-byte
				 * command.
				 */
				scsi_queue_next_request(q, SCpnt);
				result = 0;
			} else {
				SCpnt = scsi_end_request(SCpnt, 0, this_count);
				return;
			}
			break;
		case NOT_READY:
			printk(KERN_INFO "Device %s not ready.\n",
			       kdevname(SCpnt->request.rq_dev));
			SCpnt = scsi_end_request(SCpnt, 0, this_count);
			return;
			break;
		case MEDIUM_ERROR:
		case VOLUME_OVERFLOW:
			printk("scsi%d: ERROR on channel %d, id %d, lun %d, CDB: ",
			       SCpnt->host->host_no, (int) SCpnt->channel,
			       (int) SCpnt->target, (int) SCpnt->lun);
			print_command(SCpnt->cmnd);
			print_sense("sd", SCpnt);
			SCpnt = scsi_end_request(SCpnt, 0, block_sectors);
			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_queue_next_request(q, SCpnt);
		return;
	}
	if (result) {
		struct Scsi_Device_Template *STpnt;

		STpnt = scsi_get_request_dev(&SCpnt->request);
		printk("SCSI %s error : host %d channel %d id %d lun %d return code = %x\n",
		       (STpnt ? STpnt->name : "device"),
		       SCpnt->device->host->host_no,
		       SCpnt->device->channel,
		       SCpnt->device->id,
		       SCpnt->device->lun, result);

		if (driver_byte(result) & DRIVER_SENSE)
			print_sense("sd", SCpnt);
		/*
		 * Mark a single buffer as not uptodate.  Queue the remainder.
		 * We sometimes get this cruft in the event that a medium error
		 * isn't properly reported.
		 */
		SCpnt = scsi_end_request(SCpnt, 0, SCpnt->request.current_nr_sectors);
		return;
	}
}

/*
 * Function:    scsi_get_request_dev()
 *
 * Purpose:     Find the upper-level driver that is responsible for this
 *              request
 *
 * Arguments:   request   - I/O request we are preparing to queue.
 *
 * Lock status: No locks assumed to be held, but as it happens the
 *              io_request_lock is held when this is called.
 *
 * Returns:     Nothing
 *
 * Notes:       The requests in the request queue may have originated
 *              from any block device driver.  We need to find out which
 *              one so that we can later form the appropriate command.
 */
struct Scsi_Device_Template *scsi_get_request_dev(struct request *req)
{
	struct Scsi_Device_Template *spnt;
	kdev_t dev = req->rq_dev;
	int major = MAJOR(dev);

	ASSERT_LOCK(&io_request_lock, 1);

	for (spnt = scsi_devicelist; spnt; spnt = spnt->next) {
		/*
		 * Search for a block device driver that supports this
		 * major.
		 */
		if (spnt->blk && spnt->major == major) {