On Sat, 2008-01-12 at 13:25 -0600, Robert Hancock wrote: > Alexander wrote: > > Robert Hancock wrote: > >> There's this patch which was intended to fix it: > >> > >> http://lkml.org/lkml/2007/11/22/148 > > > > I applied this patch to 2.6.24-rc7. Now at boot time my DVD-RW is > > normaly detected as: > > > > sr0: scsi3-mmc drive: 48x/48x writer dvd-ram cd/rw xa/form2 cdda tray > > > > But I cannot mount it. All my attempts failed with > > > > ISOFS: Unable to identify CD-ROM format. > > > > With mem<=4098M or sata_nv.adma=0 it still mounts and works ok. > > As I wrote, it would appear that somehow the blk_queue_bounce_limit > setting that the driver has made is not being respected and the block > layer is still trying to feed it addresses over 4GB. Any ideas anyone? Actually, I'd be very sceptical that the blk_queue_bounce_limit isn't working as advertised; there'd be a large number of failures if it were not. However, the "as advertised" part doesn't seem to be generally well understood. The point being that block commands are only bounced if they come from the filesystem or the user, not if they're generated directly inside the kernel. Since the fault occurs before mount, it's suggestive of the latter. A long time ago, GFP_KERNEL allocations meant that the memory allocated was physically under 4GB. Then x86_64 (and before it ia64) wanted to break this. So they introduced a new flag: GFP_DMA32 that behaved like the old GFP_KERNEL and then changed GFP_KERNEL on their architectures to return memory from anywhere. I'd strongly suggest some piece of kernel memory was allocated for a transfer buffer without GFP_DMA32 and then passed in to the driver. Unfortunately, that could be anywhere inside cdrom or sr. Knowing what the actual command is might help ... some of the distinctive MMC media ones only have a single source. James - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
