scsi: pcmcia: nsp_cs: 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]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/pcmcia/nsp_cs.c b/drivers/scsi/pcmcia/nsp_cs.c
index a81748e..97416e1 100644 (file)
--- a/drivers/scsi/pcmcia/nsp_cs.c
+++ b/drivers/scsi/pcmcia/nsp_cs.c
@@ -789,7 +789,7 @@ static void nsp_pio_read(struct scsi_cmnd *SCpnt)
                    SCpnt->SCp.buffers_residual != 0 ) {
                        //nsp_dbg(NSP_DEBUG_DATA_IO, "scatterlist next timeout=%d", time_out);
                        SCpnt->SCp.buffers_residual--;
-                       SCpnt->SCp.buffer++;
+                       SCpnt->SCp.buffer = sg_next(SCpnt->SCp.buffer);
                        SCpnt->SCp.ptr           = BUFFER_ADDR;
                        SCpnt->SCp.this_residual = SCpnt->SCp.buffer->length;
                        time_out = 1000;
@@ -887,7 +887,7 @@ static void nsp_pio_write(struct scsi_cmnd *SCpnt)
                    SCpnt->SCp.buffers_residual != 0 ) {
                        //nsp_dbg(NSP_DEBUG_DATA_IO, "scatterlist next");
                        SCpnt->SCp.buffers_residual--;
-                       SCpnt->SCp.buffer++;
+                       SCpnt->SCp.buffer = sg_next(SCpnt->SCp.buffer);
                        SCpnt->SCp.ptr           = BUFFER_ADDR;
                        SCpnt->SCp.this_residual = SCpnt->SCp.buffer->length;
                        time_out = 1000;