From 159c54c67e8f639112a54ad18bdde4e46d0ea223 Mon Sep 17 00:00:00 2001
From: Vladislav Bolkhovitin <vst@vlnb.net>
Date: Fri, 20 Jul 2012 22:05:22 +0000
Subject: [PATCH] Improve handling of zero len unmap descriptors

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4413 d57e44dd-8a1f-0410-8b47-8ef2f437770f
---
 scst/src/dev_handlers/scst_vdisk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index 20d953af8..72a47c96a 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -1878,6 +1878,9 @@ static int vdisk_unmap_range(struct scst_cmd *cmd,
 
 	TRACE_ENTRY();
 
+	if (len == 0)
+		goto success;
+
 	if ((start > virt_dev->nblocks) ||
 	    ((start + len) > virt_dev->nblocks)) {
 		PRINT_ERROR("Device %s: attempt to write beyond max "
@@ -1947,6 +1950,7 @@ static int vdisk_unmap_range(struct scst_cmd *cmd,
 #endif
 	}
 
+success:
 	res = 0;
 
 out: