fat: Fix fat_ent_update_ptr() for FAT12

This fixes the missing update for bhs/nr_bhs in case the caller
accessed from block boundary to first block of boundary.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 5b5f49061b7c..13513992da3c 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -317,10 +317,20 @@ static inline int fat_ent_update_ptr(struct super_block *sb,
         /* Is this fatent's blocks including this entry? */
         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
                 return 0;
-        /* Does this entry need the next block? */
-        if (sbi->fat_bits == 12 && (offset + 1) >= sb->s_blocksize) {
-                if (fatent->nr_bhs != 2 || bhs[1]->b_blocknr != (blocknr + 1))
-                        return 0;
+        if (sbi->fat_bits == 12) {
+                if ((offset + 1) < sb->s_blocksize) {
+                        /* This entry is on bhs[0]. */
+                        if (fatent->nr_bhs == 2) {
+                                brelse(bhs[1]);
+                                fatent->nr_bhs = 1;
+                        }
+                } else {
+                        /* This entry needs the next block. */
+                        if (fatent->nr_bhs != 2)
+                                return 0;
+                        if (bhs[1]->b_blocknr != (blocknr + 1))
+                                return 0;
+                }
         }
         ops->ent_set_ptr(fatent, offset);
         return 1;