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

From: Glauber de Oliveira Costa
Date: Thu Feb 16 2006 - 13:43:30 EST


This is a resend of a patch I sent on Jan 20th. Andrew, could you
please consider applying it ?

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@xxxxxxxxxx>

---

fs/ext3/balloc.c | 33 +++++++++++++++++++++++++++++----
1 files changed, 29 insertions(+), 4 deletions(-)

1164cfd9b1b413f6c4b86bac11006ba2b933ccb1
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 6250fcd..8bf87b0 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -1499,6 +1499,25 @@ int ext3_bg_has_super(struct super_block
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 +1529,15 @@ int ext3_bg_has_super(struct super_block
*/
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);
+
}

--
1.0.4
-
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