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Message-Id: <1204186800.7362.7.camel@homer.simson.net>
Date: Thu, 28 Feb 2008 09:20:00 +0100
From: Mike Galbraith <efault@....de>
To: Tejun Heo <htejun@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Jens Axboe <jens.axboe@...cle.com>,
LKML <linux-kernel@...r.kernel.org>, linux-ide@...r.kernel.org,
linux-scsi@...r.kernel.org, Jeff Garzik <jgarzik@...ox.com>
Subject: Re: regression: CD burning (k3b) went broke
On Thu, 2008-02-28 at 16:43 +0900, Tejun Heo wrote:
> 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)
> 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.
> 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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