[PATCH 5.10 79/86] ext4: fix overhead calculation to account for the reserved gdt blocks

Greg Kroah-Hartman
2022-04-26T08:58:34Z

From: Theodore Ts'o <tytso@mit.edu>

commit 10b01ee92df52c8d7200afead4d5e5f55a5c58b1 upstream.

The kernel calculation was underestimating the overhead by not taking
into account the reserved gdt blocks. With this change, the overhead
calculated by the kernel matches the overhead calculation in mke2fs.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/super.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3870,9 +3870,11 @@ static int count_overhead(struct super_b
ext4_fsblk_t first_block, last_block, b;
ext4_group_t i, ngroups = ext4_get_groups_count(sb);
int s, j, count = 0;
+ int has_super = ext4_bg_has_super(sb, grp);

if (!ext4_has_feature_bigalloc(sb))
- return (ext4_bg_has_super(sb, grp) + ext4_bg_num_gdb(sb, grp) +
+ return (has_super + ext4_bg_num_gdb(sb, grp) +
+ (has_super ? le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) : 0) +
sbi->s_itb_per_group + 2);

first_block = le32_to_cpu(sbi->s_es->s_first_data_block) +