Re: memory allocation in sg_io()

[Jens Axboe <jens.axboe@oracle.com>]

On Thu, Jan 10 2008, Oliver Neukum wrote:
> Am Donnerstag, 10. Januar 2008 14:05:25 schrieb Boaz Harrosh:
> > On Thu, Jan 10 2008 at 14:33 +0200, Oliver Neukum <oliver@neukum.org> wrote:
> > > Hi,
> > > 
> > > could you explain to me why this code can get away with allocating the
> > > sense buffer on the stack?
> > > 
> > > static int sg_io(struct file *file, struct request_queue *q,
> > > 		struct gendisk *bd_disk, struct sg_io_hdr *hdr)
> > > {
> > > 	unsigned long start_time;
> > > 	int writing = 0, ret = 0, has_write_perm = 0;
> > > 	struct request *rq;
> > > 	char sense[SCSI_SENSE_BUFFERSIZE];
> > > 
> > > 	Regards
> > > 		Oliver
> > > -
> > where? what? do you mean in scsi_ioctl.c?
> > why not it's a synchronous call?
> > Do you mean 96 bytes is too big?
> > Do you mean DMA alignment and cache coherency? I'm working
> > on that for scsi devices.
> 
> Yes, you are doing DMA on the stack.

There are many offenders like that, just take a peek in cdrom.c for
instance.

-- 
Jens Axboe