Commit 1194b5ce authored by Ming Lei's avatar Ming Lei Committed by Martin K. Petersen
Browse files

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 <oliver@neukum.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 74eb7446

drivers/usb/image/microtek.c

+8 −12
Original line number Diff line number Diff line
@@ -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;

	}

drivers/usb/image/microtek.h

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ struct mts_transfer_context 
	void *data;

	unsigned data_length;

	int data_pipe;

	int fragment;

	struct scatterlist *curr_sg;



	u8 *scsi_status; /* status returned from ep_response after command completion */

};

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