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Date: Wed, 15 Apr 2009 16:48:35 +0900
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To: petkovbb@...il.com
Cc: tj@...nel.org, fujita.tomonori@....ntt.co.jp, bharrosh@...asas.com,
James.Bottomley@...senpartnership.com, linux-scsi@...r.kernel.org,
axboe@...nel.dk, bzolnier@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/17] scsi: replace custom rq mapping with
blk_rq_map_kern_sgl()
On Wed, 15 Apr 2009 09:26:55 +0200
Borislav Petkov <petkovbb@...glemail.com> wrote:
> Hi guys,
>
> On Wed, Apr 15, 2009 at 01:25:04PM +0900, Tejun Heo wrote:
> > >> Basically, I opted for preallocating a sense request in the ->do_request
> > >> routine and do that only on demand, i.e. I reinitialize it only if it
> > >> got used in the irq handler. So in case you want to shove a rq sense in
> > >> front of the queue, you simply use the already prepared one. Then in the
> > >> irq handler it is being finished the usual ways (blk_end_request). Next
> > >> time around you ->do_request, you reallocate it again since it got eaten
> > >> in the last round.
> > >
> > > Sounds a workable solution.
> >
> > Haven't actually looked at the code but sweeeeeet.
> >
> > >> The good thing is that now I don't need all those static block layer
> > >> structs in the driver (bio, bio_vec, etc) and do the preferred dynamic
> > >> allocation instead.
> > >
> > > That's surely good.
> > >
> > > Well, if you could remove the usage of request structure that are not
> > > came from blk_get_request, it will be super. But it's a different
> > > topic and Tejun can go forward without such change.
> > >
> > >> The patch is ontop of Tejun's series at
> > >> http://git.kernel.org/?p=linux/kernel/git/tj/misc.git;a=shortlog;h=ide-phase1
> > >> with some small modifications in commit 15783b1443f810ae72cb5ccb3a3a3ccc3aeb8729
> > >> wrt proper sense buffer length.
> > >
> > > I think that Tejun will drop some of the patchset. At least, we don't
> > > need blk_rq_map_kern_prealloc stuff. I think that Tejun doesn't need
> > > to play with the mapping API. Well, we need to play with the mapping
> > > API for OSD but it's not directly related with the block layer
> > > cleanups necessary for the libata SCSI separation.
> >
> > Yeah, the blk_rq_map_kern_prealloc() was basically shifting rq map
> > from ide to blk/bio so that at least codes are all in one place. If
> > it's not necessary, super. :-)
> >
> > I'll drop stuff from this and the other patchset and repost them with
> > Borislav's patch in a few hours. Thanks guys.
>
> here's a version which gets rid of the static drive->request_sense_rq
> structure and does the usual blk_get_request(), as Fujita suggested.
>
> @Tejun: we're gonna need the same thing for ide-atapi before you'll be
> able to get rid of the _prealloc() hack. I'll try to cook something up by
> tomorrow the latest.
>
> ---
> From: Borislav Petkov <petkovbb@...il.com>
> Date: Tue, 14 Apr 2009 13:24:43 +0200
> Subject: [PATCH] ide-cd: preallocate rq sense out of the irq path
>
> Preallocate a sense request in the ->do_request method and reinitialize
> it only on demand, in case it's been consumed in the IRQ handler path.
> The reason for this is that we don't want to be mapping rq to bio in
> the IRQ path and introduce all kinds of unnecessary hacks to the block
> layer.
>
> CC: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> CC: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> CC: Tejun Heo <tj@...nel.org>
> Signed-off-by: Borislav Petkov <petkovbb@...il.com>
> ---
> drivers/ide/ide-cd.c | 67 +++++++++++++++++++++++++++++---------------------
> include/linux/ide.h | 3 ++
> 2 files changed, 42 insertions(+), 28 deletions(-)
Great, thanks!
I have some comments.
> diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
> index 35d0973..82c9339 100644
> --- a/drivers/ide/ide-cd.c
> +++ b/drivers/ide/ide-cd.c
> @@ -206,32 +206,21 @@ static void cdrom_analyze_sense_data(ide_drive_t *drive,
> ide_cd_log_error(drive->name, failed_command, sense);
> }
>
> -static void cdrom_queue_request_sense(ide_drive_t *drive, void *sense,
> - struct request *failed_command)
> +static struct request *ide_cd_prep_sense(ide_drive_t *drive)
> {
> struct cdrom_info *info = drive->driver_data;
> - struct request *rq = &drive->request_sense_rq;
> - struct bio *bio = &drive->request_sense_bio;
> - struct bio_vec *bvec = drive->request_sense_bvec;
> - unsigned int bvec_len = ARRAY_SIZE(drive->request_sense_bvec);
> - unsigned sense_len = 18;
> - int error;
> + void *sense = &info->sense_data;
> + unsigned sense_len = sizeof(struct request_sense);
> + struct request *rq;
>
> ide_debug_log(IDE_DBG_SENSE, "enter");
>
> - if (sense == NULL) {
> - sense = &info->sense_data;
> - sense_len = sizeof(struct request_sense);
> - }
> -
> memset(sense, 0, sense_len);
>
> - /* stuff the sense request in front of our current request */
> - blk_rq_init(NULL, rq);
> + rq = blk_get_request(drive->queue, 0, __GFP_WAIT);
>
> - error = blk_rq_map_kern_prealloc(drive->queue, rq, bio, bvec, bvec_len,
> - sense, sense_len, true);
> - BUG_ON(error);
> + if (blk_rq_map_kern(drive->queue, rq, sense, sense_len, __GFP_WAIT))
> + return NULL;
>
> rq->rq_disk = info->disk;
>
> @@ -241,18 +230,17 @@ static void cdrom_queue_request_sense(ide_drive_t *drive, void *sense,
> rq->cmd_type = REQ_TYPE_SENSE;
> rq->cmd_flags |= REQ_PREEMPT;
>
> - /* NOTE! Save the failed command in "rq->special" */
> - rq->special = (void *)failed_command;
> -
> - if (failed_command)
> - ide_debug_log(IDE_DBG_SENSE, "failed_cmd: 0x%x",
> - failed_command->cmd[0]);
> + return rq;
> +}
>
> - drive->hwif->rq = NULL;
> +static void ide_cd_queue_rq_sense(ide_drive_t *drive)
> +{
> + BUG_ON(!drive->rq_sense);
>
> - elv_add_request(drive->queue, rq, ELEVATOR_INSERT_FRONT, 0);
> + elv_add_request(drive->queue, drive->rq_sense, ELEVATOR_INSERT_FRONT, 0);
> }
>
> +
> static void ide_cd_complete_failed_rq(ide_drive_t *drive, struct request *rq)
> {
> /*
> @@ -440,7 +428,7 @@ static int cdrom_decode_status(ide_drive_t *drive, u8 stat)
>
> /* if we got a CHECK_CONDITION status, queue a request sense command */
> if (stat & ATA_ERR)
> - cdrom_queue_request_sense(drive, NULL, NULL);
> + ide_cd_queue_rq_sense(drive);
> return 1;
>
> end_request:
> @@ -454,7 +442,7 @@ end_request:
>
> hwif->rq = NULL;
>
> - cdrom_queue_request_sense(drive, rq->sense, rq);
> + ide_cd_queue_rq_sense(drive);
> return 1;
> } else
> return 2;
> @@ -788,6 +776,10 @@ out_end:
>
> ide_complete_rq(drive, uptodate ? 0 : -EIO, nsectors << 9);
>
> + /* our sense buffer got used, reset it the next time around. */
> + if (sense)
> + drive->rq_sense = NULL;
Needs to call blk_put_request() here?
I guess that we also need to call blk_put_request() when ide_drive_s
is freed.
> +
> if (sense && rc == 2)
> ide_error(drive, "request sense failure", stat);
> }
> @@ -901,6 +893,25 @@ static ide_startstop_t ide_cd_do_request(ide_drive_t *drive, struct request *rq,
> goto out_end;
> }
>
> + /*
> + * prepare request sense if it got used with the last rq
> + */
> + if (!drive->rq_sense) {
> + drive->rq_sense = ide_cd_prep_sense(drive);
> + if (!drive->rq_sense) {
> + printk(KERN_ERR "%s: error prepping sense request!\n",
> + drive->name);
> + return ide_stopped;
> + }
> + }
> +
> + /*
> + * save the current request in case we'll be queueing a sense rq
> + * afterwards due to its potential failure.
> + */
> + if (!blk_sense_request(rq))
> + drive->rq_sense->special = (void *)rq;
> +
> memset(&cmd, 0, sizeof(cmd));
>
> if (rq_data_dir(rq))
> diff --git a/include/linux/ide.h b/include/linux/ide.h
> index c942533..4c2d310 100644
> --- a/include/linux/ide.h
> +++ b/include/linux/ide.h
> @@ -605,6 +605,9 @@ struct ide_drive_s {
> struct request request_sense_rq;
> struct bio request_sense_bio;
> struct bio_vec request_sense_bvec[2];
We can remove the above, right?
> +
> + /* current sense rq */
> + struct request *rq_sense;
> };
>
> typedef struct ide_drive_s ide_drive_t;
> --
> 1.6.2.2
>
>
> --
> Regards/Gruss,
> Boris.
> --
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