[SCSI] sr: consider the last written sector when determining media size

On certain cases, UDF disc doesn't report capacity correctly via
READ_CAPACITY but TOC or trackinfo contains valid information which
can be obtained using cdrom_get_last_written().  ide-cd considers both
values and uses the larger one.  Do the same in sr.  This fixes
bko#9668.

 http://bugzilla.kernel.org/show_bug.cgi?id=9668

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Milan Kocian <milan.kocian@wq.cz>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/sr.c

@@ -684,14 +684,20 @@ static void get_sectorsize(struct scsi_cd *cd)
 		cd->capacity = 0x1fffff;
 		sector_size = 2048;	/* A guess, just in case */
 	} else {
-#if 0
-		if (cdrom_get_last_written(&cd->cdi,
-					   &cd->capacity))
-#endif
-			cd->capacity = 1 + ((buffer[0] << 24) |
-						    (buffer[1] << 16) |
-						    (buffer[2] << 8) |
-						    buffer[3]);
+		long last_written;
+
+		cd->capacity = 1 + ((buffer[0] << 24) | (buffer[1] << 16) |
+				    (buffer[2] << 8) | buffer[3]);
+		/*
+		 * READ_CAPACITY doesn't return the correct size on
+		 * certain UDF media.  If last_written is larger, use
+		 * it instead.
+		 *
+		 * http://bugzilla.kernel.org/show_bug.cgi?id=9668
+		 */
+		if (!cdrom_get_last_written(&cd->cdi, &last_written))
+			cd->capacity = max_t(long, cd->capacity, last_written);
+
 		sector_size = (buffer[4] << 24) |
 		    (buffer[5] << 16) | (buffer[6] << 8) | buffer[7];
 		switch (sector_size) {