From: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Date: Tue, 29 Aug 2017 03:23:53 +0000 (-0700)
Subject: storvsc: don't assume SG list is contiguous
X-Git-Tag: v4.1.12-117.0_27200813_3~136
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8b7ea6a165d99ee6b3b49b4861999acc2055c2e1;p=users%2Fjedix%2Flinux-maple.git

storvsc: don't assume SG list is contiguous

Scatterlists are contiguous if they're limited to a page; but for large
I/Os, it's possible that the scatterlists span pages, in which case the
pages will not be physically contiguous - they will be chained together.
The MS patch (link below) fixes the wrong assumption in do_bounce_buffer()
that scatterlists are always contiguous, so it's a good fix to port, in
general.

Orabug: 26492697

MS patch:
https://github.com/LIS/lis-next/commit/a13bbc4ab81e459f635237a938f89737300ecfa1

Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Reviewed-by: Joe Slember <joe.slember@oracle.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
---

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index dbc9d9a1c89d..b08fa4b87f75 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -575,17 +575,18 @@ static int do_bounce_buffer(struct scatterlist *sgl, unsigned int sg_count)
 	for (i = 0; i < sg_count; i++) {
 		if (i == 0) {
 			/* make sure 1st one does not have hole */
-			if (sgl[i].offset + sgl[i].length != PAGE_SIZE)
+			if (sgl->offset + sgl->length != PAGE_SIZE)
 				return i;
 		} else if (i == sg_count - 1) {
 			/* make sure last one does not have hole */
-			if (sgl[i].offset != 0)
+			if (sgl->offset != 0)
 				return i;
 		} else {
 			/* make sure no hole in the middle */
-			if (sgl[i].length != PAGE_SIZE || sgl[i].offset != 0)
+			if (sgl->length != PAGE_SIZE || sgl->offset != 0)
 				return i;
 		}
+		sgl = sg_next(sgl);
 	}
 	return -1;
 }