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 <[email protected]>
>
> 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 <[email protected]>
> ---
> 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?
--
Jens Axboe
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