From: Dongli Zhang <dongli.zhang@oracle.com>
Date: Wed, 23 Jan 2019 07:48:36 +0000 (+0800)
Subject: xen/blkback: rework validate_io_op()
X-Git-Tag: v4.1.12-124.31.3~303
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ebd6f4c1518234182cf6c36f060c40b519b487bf;p=users%2Fjedix%2Flinux-maple.git

xen/blkback: rework validate_io_op()

Rework many if statements in validate_io_op() into a switch statement.

Orabug: 29199843

Suggested-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 1f892410342a9..e14b87c422667 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1148,33 +1148,43 @@ static bool validate_io_op(const struct blkif_request *req, unsigned int nseg)
 	unsigned short req_operation = req->operation == BLKIF_OP_INDIRECT ?
 			req->u.indirect.indirect_op : req->operation;
 
-	if (unlikely(req_operation == BLKIF_OP_RESERVED_1))
+	switch (req_operation) {
+	case BLKIF_OP_RESERVED_1:
 		goto fail;
 
-	/* For discard, nseg is not meaninful */
-	if (unlikely(req_operation == BLKIF_OP_DISCARD))
+	case BLKIF_OP_DISCARD:
+		/* For discard, nseg is not meaninful */
 		return true;
 
-	if ((req_operation > BLKIF_OP_INDIRECT) ||	/* valid operation? */
-	    ((req->operation == BLKIF_OP_INDIRECT) &&	/* valid indirect-op */
-	     (req_operation != BLKIF_OP_READ) &&
-	     (req_operation != BLKIF_OP_WRITE))) {
-		goto fail;
-	}
-
-	if (unlikely(nseg == 0)) { /* if nseg == 0, is op in the correct set? */
-		if (req_operation != BLKIF_OP_FLUSH_DISKCACHE &&
-		    req_operation != BLKIF_OP_WRITE_BARRIER)
+	case BLKIF_OP_READ:
+	case BLKIF_OP_WRITE:
+		/* if nseg == 0, is op in the correct set? */
+		if (unlikely(nseg == 0))
 			goto fail;
-	} else { /* if nseg > 0, check if nseg makes sense. */
-		if (((req->operation != BLKIF_OP_INDIRECT) &&
-			(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
-		    ((req->operation == BLKIF_OP_INDIRECT) &&
-			(nseg > MAX_INDIRECT_SEGMENTS))) {
+		break;
+
+	case BLKIF_OP_WRITE_BARRIER:
+	case BLKIF_OP_FLUSH_DISKCACHE:
+		/* not valid indirect-op */
+		if (req->operation == BLKIF_OP_INDIRECT)
 			goto fail;
-		}
+		break;
+
+	default:
+		/* req_operation should never >= BLKIF_OP_INDIRECT */
+		goto fail;
 	}
 
+	/* if nseg > 0, check if nseg makes sense. */
+	if (req->operation != BLKIF_OP_INDIRECT &&
+	    nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)
+		goto fail;
+
+	/* if nseg > 0, check if nseg makes sense. */
+	if (req->operation == BLKIF_OP_INDIRECT &&
+	    nseg > MAX_INDIRECT_SEGMENTS)
+		goto fail;
+
 	return true;
 fail:
 	pr_debug("Invalid indirect operation or bad number of "