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 1f892410342a9707b9aa6df5030135814313d5df..e14b87c422667dbe4e56679f5f4e435b9655e9cb 100644 (file)
--- 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 "