scsi: staging: unisys: visorhba: 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: devel@driverdev.osuosl.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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/staging/unisys/visorhba/visorhba_main.c b/drivers/staging/unisys/visorhba/visorhba_main.c
index 2dad36a055188f6f6917a5094dcbc761071f2670..dd979ee4dcf10c6d9364867da7ae8a8404e68c6e 100644 (file)
--- a/drivers/staging/unisys/visorhba/visorhba_main.c
+++ b/drivers/staging/unisys/visorhba/visorhba_main.c
@@ -871,12 +871,11 @@ static void do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp,
                        return;
                }
 
-               sg = scsi_sglist(scsicmd);
-               for (i = 0; i < scsi_sg_count(scsicmd); i++) {
-                       this_page_orig = kmap_atomic(sg_page(sg + i));
+               scsi_for_each_sg(scsicmd, sg, scsi_sg_count(scsicmd), i) {
+                       this_page_orig = kmap_atomic(sg_page(sg));
                        this_page = (void *)((unsigned long)this_page_orig |
-                                            sg[i].offset);
-                       memcpy(this_page, buf + bufind, sg[i].length);
+                                            sg->offset);
+                       memcpy(this_page, buf + bufind, sg->length);
                        kunmap_atomic(this_page_orig);
                }
                kfree(buf);