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SubjectRe: [PATCH] ide-cd: use blk_get_request()
On Thu, 8 Jun 2006 08:30:00 +0200 Jens Axboe wrote:

> On Wed, Jun 07 2006, Randy.Dunlap wrote:
> > On Wed, 7 Jun 2006 08:22:08 +0200 Jens Axboe wrote:
> >
> > > On Tue, Jun 06 2006, Andrew Morton wrote:
> > > >
> > > > Note that Laurent is also passing through ide_cdrom_packet(), which has a
> > > > `struct request' on the stack. The kernel does this in a lot of places,
> > > > and at 168 bytes on x86, it'd really be best if we were to dynamically
> > > > allocate these things.
> > >
> > > That's an old peeve of mine, on-stack requests... It's nasty from
> > > several angles, stack usage just being one of them. Perhaps I'll give it
> > > a go for 2.6.18 and add checks for request being thrown at the block
> > > layer which didn't originate from get_request().
> >
> > This is a start at converting ide-cd.c to use blk_get_request().
> > How does it look so far?
> > It builds, but I have not tested it yet.
> > And of course, there are other drivers to be modified as well.
> >
> > ---
> > From: Randy Dunlap <rdunlap@xenotime.net>
> >
> > Convert struct request req; on function stacks to
> > use allocation via blk_get_request() to
> > (a) reduce stack pressure and
> > (b) use centralized blk_ functions and
> > (c) allow for block IO tracing.
> >
> > Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
> > ---
> > drivers/ide/ide-cd.c | 258 +++++++++++++++++++++++++++++++++------------------
> > 1 files changed, 170 insertions(+), 88 deletions(-)
> >
> > --- linux-2617-rc6.orig/drivers/ide/ide-cd.c
> > +++ linux-2617-rc6/drivers/ide/ide-cd.c
> > @@ -2033,24 +2033,32 @@ int msf_to_lba (byte m, byte s, byte f)
> >
> > static int cdrom_check_status(ide_drive_t *drive, struct request_sense *sense)
> > {
> > - struct request req;
> > + struct request *req;
> > struct cdrom_info *info = drive->driver_data;
> > struct cdrom_device_info *cdi = &info->devinfo;
> > + request_queue_t *q = cdi->disk->queue;
> > + int stat;
> >
> > - cdrom_prepare_request(drive, &req);
> > -
> > - req.sense = sense;
> > - req.cmd[0] = GPCMD_TEST_UNIT_READY;
> > - req.flags |= REQ_QUIET;
> > + req = blk_get_request(q, READ, GFP_KERNEL);
> > + if (!req)
> > + return -ENOMEM;
> > +
> > + cdrom_prepare_request(drive, req);
>
> This cannot work, have you seen what cdrom_prepare_request() does?

Obviously not.
(It calls ide_init_drive_cmd(), which clears the <request>.)

Thanks.
---
~Randy
-
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