On Sun, 2006-10-01 at 15:40 -0500, James Bottomley wrote: > On Sun, 2006-10-01 at 22:13 +0200, Andi Kleen wrote: > > GFP_DMA in general is deprecated and should be replaced by appropiate > > dma_alloc_coherent() > > Um, no it shouldn't. > > All of the places where we use GFP_DMA are because we might be > addressing an ISA card or other strange mask limited card (gated usually > by unchecked_isa_dma). However, what is wanted in every case is > ordinary memory, not coherent memory. They can't simply be replaced > with dma_alloc_coherent because > > a) it will waste memory for platforms that only do it in page size > multiples > b) It will fail on platforms that can't do it at all. > > Coherent memory is really only for device drivers to use in mailboxes > and shared ring buffers. > > > or similar. And I can't imagine any modern systems still need them, and for > > the few still non CONFIG_BROKEN ISA drivers maybe some other way can be found? > > And do they really require the mid layer data structures to be GFP_DMA too? > > Well, it's the "or similar" that's still the problem. All they need is > ordinary memory which respects the device mask (then I can get rid of > the unchecked_isa_dma flag as well). > > One could argue, I suppose, that when we get every SCSI path to go via > sg, then the block layer will bounce this for us, and we don't need to > worry at all. I think we might just need the blk_map_kern users now. For the async execute I added the bounce code already and the block SG_IO has it atleady. I think the blk_map_kern bounce code got dropped because we thought the correct gfp_t would be passed in. But I think all we need is the patch below and all the paths are take care of. The patch is not tested. Patch was made against scsi-misc. The last place that is sending non sg commands may just be md/dm-emc.c but that is is just waiting on alasdair to take some patches that fix that and a bunch of junk in there including adding bounce support. If the patch below is ok though and dm-emc finally gets converted then it will have sg and bonce buffer support. Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx> diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index 9c3a06b..e58b43a 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -2533,6 +2533,7 @@ int blk_rq_map_kern(request_queue_t *q, rq->bio = rq->biotail = bio; blk_rq_bio_prep(q, rq, bio); + blk_queue_bounce(q, &rq->bio); rq->buffer = rq->data = NULL; rq->data_len = len; return 0; diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c diff --git a/fs/bio.c b/fs/bio.c - 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
