On Tue, May 20, 2008 at 01:58:30PM +0900, FUJITA Tomonori wrote: > The goal of this patchset is reverting the commit > 22a9189fd073db3d03a4cf8b8c098aa207602de1 (cdrom: use kmalloced buffers > instead of buffers on stack). > > http://lkml.org/lkml/2008/4/21/634 > > The commit is using kmalloced buffers for cdrom packet commands to > avoid stack corruption on non coherent platforms. But allocating a > small buffer like this is not nice (unnecessary complicity): > > + buffer = kmalloc(8, GFP_KERNEL); If I read the bio code correctly with your patch non coherent system will be punished a lot more. bio_copy_kern will allocate a whole page for this 8 bytes. Please correct me, if I'm wrong otherwise I tend to NAK that approach. > If some architectures can't do DMA on stack, we also need to a new > queue_flag like QUEUE_FLAG_NO_DMA_ON_STACK in addtion of this > patchset. DMA-mapping.txt tells that DMA on stack is forbidden. IMHO we either need to revoke that first or deal with it. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessary a good idea. [ RFC1925, 2.3 ] -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
