On Thu, 2008-02-28 at 16:43 +0900, Tejun Heo wrote:
quoted text
> Hello, all.
> 
> Sorry about the delay.  Was buried under other stuff.  Mike, thanks a
> lot for reporting and analyzing the problem; however, the patch is
> slightly incorrect.  rq->data_len is rq->data_len + extra stuff for
> alignment and padding, so the correct thing to do is...
> 
>   req->raw_data_len -= req->data_len - scsi_get_resid(cmd);
>   req->data_len = scsi_get_resid(cmd);

Ah, close but no banana.  (feeds poor wingless patchlet to bit-wolf)

quoted text
> which is ugly and error-prone.  In addition, this isn't the only place
> where resid is set.  Other block drivers do this too.  This definitely
> should be done in block layer.
> 
> With rq->data_len and rq->raw_data_len, it's impossible to translate
> resid of rq->data_len to resid of rq->raw_data_len as block layer
> doesn't know how much was extra data after rq->data_len is modified.
> The attached patch substitutes rq->raw_data_len w/ rq->extra_len and
> adds blk_rq_raw_data_len().  Things look cleaner this way and the resid
> problem should be solved with this.
> 
> Can you please verify the attached patch fixes the problem?
> 
> Thanks.

Thank you, works fine.

quoted text
> plain text document attachment (patch)
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 775c851..929ab61 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -127,7 +127,7 @@ void rq_init(struct request_queue *q, struct request *rq)
>  	rq->nr_hw_segments = 0;
>  	rq->ioprio = 0;
>  	rq->special = NULL;
> -	rq->raw_data_len = 0;
> +	rq->extra_len = 0;
>  	rq->buffer = NULL;
>  	rq->tag = -1;
>  	rq->errors = 0;
> @@ -2016,7 +2016,6 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
>  	rq->hard_cur_sectors = rq->current_nr_sectors;
>  	rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
>  	rq->buffer = bio_data(bio);
> -	rq->raw_data_len = bio->bi_size;
>  	rq->data_len = bio->bi_size;
>  
>  	rq->bio = rq->biotail = bio;
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 09f7fd0..c67a75f 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -19,7 +19,6 @@ int blk_rq_append_bio(struct request_queue *q, struct request *rq,
>  		rq->biotail->bi_next = bio;
>  		rq->biotail = bio;
>  
> -		rq->raw_data_len += bio->bi_size;
>  		rq->data_len += bio->bi_size;
>  	}
>  	return 0;
> @@ -156,6 +155,7 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
>  		bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len;
>  		bio->bi_size += pad_len;
>  		rq->data_len += pad_len;
> +		rq->extra_len += pad_len;
>  	}
>  
>  	rq->buffer = rq->data = NULL;
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 7506c4f..efb5b4d 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -232,6 +232,7 @@ new_segment:
>  			    (PAGE_SIZE - 1));
>  		nsegs++;
>  		rq->data_len += q->dma_drain_size;
> +		rq->extra_len += q->dma_drain_size;
>  	}
>  
>  	if (sg)
> diff --git a/block/bsg.c b/block/bsg.c
> index 7f3c095..81b2133 100644
> --- a/block/bsg.c
> +++ b/block/bsg.c
> @@ -437,14 +437,14 @@ static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr,
>  	}
>  
>  	if (rq->next_rq) {
> -		hdr->dout_resid = rq->raw_data_len;
> -		hdr->din_resid = rq->next_rq->raw_data_len;
> +		hdr->dout_resid = blk_rq_raw_data_len(rq);
> +		hdr->din_resid = blk_rq_raw_data_len(rq->next_rq);
>  		blk_rq_unmap_user(bidi_bio);
>  		blk_put_request(rq->next_rq);
>  	} else if (rq_data_dir(rq) == READ)
> -		hdr->din_resid = rq->raw_data_len;
> +		hdr->din_resid = blk_rq_raw_data_len(rq);
>  	else
> -		hdr->dout_resid = rq->raw_data_len;
> +		hdr->dout_resid = blk_rq_raw_data_len(rq);
>  
>  	/*
>  	 * If the request generated a negative error number, return it
> diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
> index e993cac..32424b3 100644
> --- a/block/scsi_ioctl.c
> +++ b/block/scsi_ioctl.c
> @@ -266,7 +266,7 @@ static int blk_complete_sghdr_rq(struct request *rq, struct sg_io_hdr *hdr,
>  	hdr->info = 0;
>  	if (hdr->masked_status || hdr->host_status || hdr->driver_status)
>  		hdr->info |= SG_INFO_CHECK;
> -	hdr->resid = rq->raw_data_len;
> +	hdr->resid = blk_rq_raw_data_len(rq);
>  	hdr->sb_len_wr = 0;
>  
>  	if (rq->sense_len && hdr->sbp) {
> @@ -528,8 +528,8 @@ static int __blk_send_generic(struct request_queue *q, struct gendisk *bd_disk,
>  	rq = blk_get_request(q, WRITE, __GFP_WAIT);
>  	rq->cmd_type = REQ_TYPE_BLOCK_PC;
>  	rq->data = NULL;
> -	rq->raw_data_len = 0;
>  	rq->data_len = 0;
> +	rq->extra_len = 0;
>  	rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
>  	memset(rq->cmd, 0, sizeof(rq->cmd));
>  	rq->cmd[0] = cmd;
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 0562b0a..5cab84c 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -2539,7 +2539,8 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
>  	 * want to set it properly, and for DMA where it is
>  	 * effectively meaningless.
>  	 */
> -	nbytes = min(scmd->request->raw_data_len, (unsigned int)63 * 1024);
> +	nbytes = min(blk_rq_raw_data_len(scmd->request),
> +		     (unsigned int)63 * 1024);
>  
>  	/* Most ATAPI devices which honor transfer chunk size don't
>  	 * behave according to the spec when odd chunk size which
> diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 6fe67d1..57e2a9e 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -216,8 +216,8 @@ struct request {
>  	unsigned int cmd_len;
>  	unsigned char cmd[BLK_MAX_CDB];
>  
> -	unsigned int raw_data_len;
>  	unsigned int data_len;
> +	unsigned int extra_len;
>  	unsigned int sense_len;
>  	void *data;
>  	void *sense;
> @@ -477,6 +477,11 @@ enum {
>  
>  #define rq_data_dir(rq)		((rq)->cmd_flags & 1)
>  
> +static inline unsigned int blk_rq_raw_data_len(struct request *rq)
> +{
> +	return rq->data_len - min(rq->extra_len, rq->data_len);
> +}
> +
>  /*
>   * We regard a request as sync, if it's a READ or a SYNC write.
>   */

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