[PATCH] UDF: fix anchor point detection

[Pavel Emelyanov <xemul@openvz.org>]

According to ECMA 167 rev. 3 (see 3/8.4.2.1), Anchor Volume
Descriptor Pointer should be recorded at two or more anchor 
points located at sectors 256, N, N - 256, where N - is a 
largest logical sector number at volume space.

So we should always try to detect N on UDF volume before 
trying to find Anchor Volume Descriptor (i.e. calling to 
udf_find_anchor()).

That said, all this patch does is updates the s_last_block 
even if the udf_vrs() returns positive value.

Originally written and tested by Yuri Per, ported on latest 
mainline by me.

Signed-off-by: Yuri Per <Yuri.Per@acronis.com>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Max Lyadvinsky <Max.Lyadvinsky@acronis.com>
Cc: Vladimir Simonov <Vladimir.Simonov@acronis.com>
Cc: Andrew Neporada <Andrew.Neporada@acronis.com>
Cc: Kirill Korotaev <dev@openvz.org>

---

diff --git a/fs/udf/super.c b/fs/udf/super.c
index f3ac4ab..abd5e30 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1486,16 +1486,17 @@ static int udf_check_valid(struct super_block *sb, int novrs, int silent)
 	/* Check that it is NSR02 compliant */
 	/* Process any "CD-ROM Volume Descriptor Set" (ECMA 167 2/8.3.1) */
 	else {
+		struct udf_sb_info *sbi = UDF_SB(sb);
+
 		block = udf_vrs(sb, silent);
-		if (block == -1) {
-			struct udf_sb_info *sbi = UDF_SB(sb);
+		if (block == -1)
 			udf_debug("Failed to read byte 32768. Assuming open "
 				  "disc. Skipping validity check\n");
-			if (!sbi->s_last_block)
-				sbi->s_last_block = udf_get_last_block(sb);
-			return 0;
-		} else
-			return !block;
+
+		if (block && !sbi->s_last_block)
+			sbi->s_last_block = udf_get_last_block(sb);
+
+		return !block;
 	}
 }