udf: Improve anchor block detection

Add <last block>+1 and <last block>-1 to a list of blocks which can be the
real last recorded block on a UDF media. Sebastian Manciulea
<manciuleas@yahoo.com> claims this helps some drive + media combinations
he is able to test.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 9 insertions, 4 deletions

diff --git a/fs/udf/super.c b/fs/udf/super.c
index fe0dafebde7..b9e719de070 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -709,14 +709,16 @@ static int udf_check_anchor_block(struct super_block *sb, sector_t block,
 static sector_t udf_scan_anchors(struct super_block *sb, bool varconv,
                                         sector_t lastblock)
 {
-        sector_t last[4];
+        sector_t last[6];
         int i;
         struct udf_sb_info *sbi = UDF_SB(sb);
 
         last[0] = lastblock;
-        last[1] = last[0] - 2;
-        last[2] = last[0] - 150;
-        last[3] = last[0] - 152;
+        last[1] = last[0] - 1;
+        last[2] = last[0] + 1;
+        last[3] = last[0] - 2;
+        last[4] = last[0] - 150;
+        last[5] = last[0] - 152;
 
         /*  according to spec, anchor is in either:
          *     block 256
@@ -727,6 +729,9 @@ static sector_t udf_scan_anchors(struct super_block *sb, bool varconv,
         for (i = 0; i < ARRAY_SIZE(last); i++) {
                 if (last[i] < 0)
                         continue;
+                if (last[i] >= sb->s_bdev->bd_inode->i_size >>
+                                sb->s_blocksize_bits)
+                        continue;
 
                 if (udf_check_anchor_block(sb, last[i], varconv)) {
                         sbi->s_anchor[0] = last[i];