Theodore Tso wrote:
On Wed, Nov 11, 2009 at 01:09:00PM +0100, Damien Guibouret wrote:
Yup, you're right. Ouch. That is a kernel bug, and it means that if
we resize a filesystem to the point where we need to use meta_bg
(because we've run out of blocks to reserve), if there are
uninitialized block bitmaps, kernels that don't have a fix will
misbehave by reserving too many file system metadata blocks. This
will waste bit of disk space, which fsck will fix.
(s_first_meta_bg by definition is always less than or equal to
s_gdb_count.)
I think this patch should fix things up.
- Ted
commit b33c339814f97fc48a843f45f6068f84bc735141
Author: Theodore Ts'o <tytso@xxxxxxx>
Date: Sat Nov 14 23:20:30 2009 -0500
ext4: Fix uninit block bitmap initialization when s_meta_first_bg is non-zero
The number of old-style block group descriptor blocks is
s_meta_first_bg when the meta_bg feature flag is set.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 1d04189..f3032c9 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -761,7 +761,13 @@ static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
ext4_group_t group)
{
- return ext4_bg_has_super(sb, group) ? EXT4_SB(sb)->s_gdb_count : 0;
+ if (!ext4_bg_has_super(sb, group))
+ return 0;
+
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
+ return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
+ else
+ return EXT4_SB(sb)->s_gdb_count;
}
/**
Hello,
I've open a kernel bug since:
http://bugzilla.kernel.org/show_bug.cgi?id=14601
with a proposed patch (little different from yours but it is matter of
taste :)
And I think there is some other places where kernel should be fixed when
it uses s_gdb_count (but here my knowledge of the sources are not deep
enough to be sure on what shall be performed).
Regards,
Damien
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