From 1194b5ce57d27c2ad49ed26f8cec98757c7c23ec Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 18 Jun 2019 09:37:48 +0800 Subject: scsi: usb: image: microtek: use sg helper to iterate over scatterlist Unlike the legacy I/O path, scsi-mq preallocates a large array to hold the scatterlist for each request. This static allocation can consume substantial amounts of memory on modern controllers which support a large number of concurrently outstanding requests. To facilitate a switch to a smaller static allocation combined with a dynamic allocation for requests that need it, we need to make sure all SCSI drivers handle chained scatterlists correctly. Convert remaining drivers that directly dereference the scatterlist array to using the iterator functions. [mkp: clarified commit message] Cc: Oliver Neukum Cc: Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org Reviewed-by: Bart Van Assche Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Martin K. Petersen --- drivers/usb/image/microtek.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) (limited to 'drivers/usb/image/microtek.c') diff --git a/drivers/usb/image/microtek.c b/drivers/usb/image/microtek.c index 607be1f4fe27..0a57c2cc8e5a 100644 --- a/drivers/usb/image/microtek.c +++ b/drivers/usb/image/microtek.c @@ -488,7 +488,6 @@ static void mts_command_done( struct urb *transfer ) static void mts_do_sg (struct urb* transfer) { - struct scatterlist * sg; int status = transfer->status; MTS_INT_INIT(); @@ -500,13 +499,12 @@ static void mts_do_sg (struct urb* transfer) mts_transfer_cleanup(transfer); } - sg = scsi_sglist(context->srb); - context->fragment++; + context->curr_sg = sg_next(context->curr_sg); mts_int_submit_urb(transfer, context->data_pipe, - sg_virt(&sg[context->fragment]), - sg[context->fragment].length, - context->fragment + 1 == scsi_sg_count(context->srb) ? + sg_virt(context->curr_sg), + context->curr_sg->length, + sg_is_last(context->curr_sg) ? mts_data_done : mts_do_sg); } @@ -526,22 +524,20 @@ static void mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc) { int pipe; - struct scatterlist * sg; - + MTS_DEBUG_GOT_HERE(); desc->context.instance = desc; desc->context.srb = srb; - desc->context.fragment = 0; if (!scsi_bufflen(srb)) { desc->context.data = NULL; desc->context.data_length = 0; return; } else { - sg = scsi_sglist(srb); - desc->context.data = sg_virt(&sg[0]); - desc->context.data_length = sg[0].length; + desc->context.curr_sg = scsi_sglist(srb); + desc->context.data = sg_virt(desc->context.curr_sg); + desc->context.data_length = desc->context.curr_sg->length; } -- cgit v1.2.3