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); I tried to remove generic_packet() and convert cdrom users to use the block queue like pkt_generic_packet (as Jens suggested in the thread if I correctly understand), but it turned out that it needs tricky surgery (like handling ssleep and retries for packet commands in ide). Then I found that we can easily handle packet commands on non coherent platforms. The diffstat is pretty small except for the revert. All this patchset does is just setting the dma_pad_mask to ARCH_KMALLOC_MINALIGN. Only scsi and ide-cd do DMA generic_packet. In the case of scsi, sr_packet uses blk_rq_map_kern (the commit 68154e90c9d1492d570671ae181d9a8f8530da55) post 2.6.25. So if we set the dma padding on non coherent platforms, sr_packet uses allocated pages properly. In the case of IDE, ide-cd has a mechanism to handle alignment and padding for SG_IO. So we can easily exploit it for packet commands. 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. The diffstat is: block/blk-settings.c | 30 +++++- drivers/ata/libata-scsi.c | 3 +- drivers/cdrom/cdrom.c | 274 +++++++++++++++------------------------------ drivers/ide/ide-cd.c | 17 ++- include/linux/blkdev.h | 1 + 5 files changed, 134 insertions(+), 191 deletions(-) -- 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
