[PATCH] ext3: Properly report backup block present in a group

In filesystems with the meta block group flag on, ext3_bg_num_gdb() fails
to report the correct number of blocks used to store the group descriptor
backups in a given group.  It happens because meta_bg follows a different
logic from the original ext3 backup placement in groups multiples of 3, 5
and 7.

Signed-off-by: Glauber de Oliveira Costa <glommer@br.ibm.com>
Cc: Andreas Dilger <adilger@clusterfs.com>
Cc: "Stephen C. Tweedie" <sct@redhat.com>
Cc: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 33 insertions, 7 deletions

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 6250fcdf14a1..46623f77666b 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1493,12 +1493,33 @@ static int ext3_group_sparse(int group)
  */
 int ext3_bg_has_super(struct super_block *sb, int group)
 {
-        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
-            !ext3_group_sparse(group))
+        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,
+                                EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
+                        !ext3_group_sparse(group))
                 return 0;
         return 1;
 }
 
+static unsigned long ext3_bg_num_gdb_meta(struct super_block *sb, int group)
+{
+        unsigned long metagroup = group / EXT3_DESC_PER_BLOCK(sb);
+        unsigned long first = metagroup * EXT3_DESC_PER_BLOCK(sb);
+        unsigned long last = first + EXT3_DESC_PER_BLOCK(sb) - 1;
+
+        if (group == first || group == first + 1 || group == last)
+                return 1;
+        return 0;
+}
+
+static unsigned long ext3_bg_num_gdb_nometa(struct super_block *sb, int group)
+{
+        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,
+                                EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
+                        !ext3_group_sparse(group))
+                return 0;
+        return EXT3_SB(sb)->s_gdb_count;
+}
+
 /**
  *      ext3_bg_num_gdb - number of blocks used by the group table in group
  *      @sb: superblock for filesystem
@@ -1510,9 +1531,14 @@ int ext3_bg_has_super(struct super_block *sb, int group)
  */
 unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
 {
-        if (EXT3_HAS_RO_COMPAT_FEATURE(sb,EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER)&&
-            !ext3_group_sparse(group))
-                return 0;
-        return EXT3_SB(sb)->s_gdb_count;
-}
+        unsigned long first_meta_bg =
+                        le32_to_cpu(EXT3_SB(sb)->s_es->s_first_meta_bg);
+        unsigned long metagroup = group / EXT3_DESC_PER_BLOCK(sb);
+
+        if (!EXT3_HAS_INCOMPAT_FEATURE(sb,EXT3_FEATURE_INCOMPAT_META_BG) ||
+                        metagroup < first_meta_bg)
+                return ext3_bg_num_gdb_nometa(sb,group);
 
+        return ext3_bg_num_gdb_meta(sb,group);
+
+}