[DRBD-cvs] svn commit by lars - r2451 - trunk/drbd - grmbl... don't dereference what is a NULL pointer most

[drbd-cvs at lists.linbit.com]

Author: lars
Date: 2006-09-23 13:39:56 +0200 (Sat, 23 Sep 2006)
New Revision: 2451

Modified:
   trunk/drbd/drbd_req.c
Log:
grmbl... don't dereference what is a NULL pointer most of the time...

Modified: trunk/drbd/drbd_req.c
===================================================================
--- trunk/drbd/drbd_req.c	2006-09-23 10:15:40 UTC (rev 2450)
+++ trunk/drbd/drbd_req.c	2006-09-23 11:39:56 UTC (rev 2451)
@@ -1122,14 +1122,17 @@
 	limit = AL_EXTENT_SIZE - ((bio_offset & (AL_EXTENT_SIZE-1)) + bio_size);
 #endif
 	if (limit < 0) limit = 0;
-	if (limit <= bvec->bv_len && bio_size == 0)
-		limit = bvec->bv_len;
-
-	if(limit && inc_local(mdev)) {
-		backing_limit = mdev->bc->bmbf(q,bio,bvec);
-		limit = min(limit,backing_limit);
+	if (bio_size == 0) {
+		if (limit <= bvec->bv_len) limit = bvec->bv_len;
+	} else if (limit && inc_local(mdev)) {
+		/* FIXME
+		 * I don't think taking a shortcut is valid, the backing device
+		 * is allowed to change its merge bvec function anytime... */
+		if (mdev->bc->bmbf) {
+			backing_limit = mdev->bc->bmbf(q,bio,bvec);
+			limit = min(limit,backing_limit);
+		}
 		dec_local(mdev);
 	}
-
 	return limit;
 }