target: Fix range calculation in WRITE SAME emulation when num blocks…

… == 0

When NUMBER OF LOGICAL BLOCKS is 0, WRITE SAME is supposed to write
all the blocks from the specified LBA through the end of the device.
However, dev->transport->get_blocks(dev) (perhaps confusingly) returns
the last valid LBA rather than the number of blocks, so the correct
number of blocks to write starting with lba is

dev->transport->get_blocks(dev) - lba + 1

(nab: Backport roland's for-3.6 patch to for-3.5)

Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_cdb.c

@@ -1095,7 +1095,7 @@ int target_emulate_write_same(struct se_cmd *cmd)
 	if (num_blocks != 0)
 		range = num_blocks;
 	else
-		range = (dev->transport->get_blocks(dev) - lba);
+		range = (dev->transport->get_blocks(dev) - lba) + 1;
 
 	pr_debug("WRITE_SAME UNMAP: LBA: %llu Range: %llu\n",
 		 (unsigned long long)lba, (unsigned long long)range);